One blemished one's underwear

[Effem]

Last night I switched on my system to warm up ready for my usual nightly listening sesh, put the kettle on for a cuppa, opened the package containing the new Adele album that arrived yesterday morning to give that a whirl in the CD player.

Played track number 1 fine, around 10 seconds into track 2 the speakers let out the biggest bang you could ever imagine AND I INSTANTLY BLEMISHED MY UNDERWEAR :( I stood there in total shock expecting a huge cloud of acrid smoke from either the amp or speakers - my ears were still ringing a minute later, but no signs of smoke, no smell of burning and the CD was happily playing away at the same low volume level I had it at. Amp was as warm as normal, sniffed around the vents and no telltale smells emanating from it, placed my finger gently on all the bass/mid cones and they were doing as they should be doing. Ear pressed to each tweeter - fine.

I am donald ducked if I know what on earth caused this massive bang. I didn't notice the lights dim or brighten (perhaps they did), the missus said the telly and lights in the lounge were fine. If it was a mains surge, the the Belkin PF30 should have caught that one would assume :scratch:

Any road up, despite much trepidation and nail biting, I listened to the rest of Adele at low volume, then played the whole of Yello's Baby and cranked the volume up halfway - was fine.

[Alex_UK]

Sorry to hear that Frank. Hopefully some of the clever members will be able to offer a technical theory on what happened, but at least it doesn't sound like any damage was done to the speakers. :( Let's hope it was a one-off.

(PS - I might finally cave in and get the Adele albums today.)

[Barry]

Has the problem re-occured Frank? In other words, 10 seconds into track 2 of the same CD.

The only thing that occurs to me, is that it might be static discharge from the disc. Unlikely, I know and something that has never happened to me.

Suggest you use a 'Hot wash' for the concomitant 'problem'.

Regards

[electric beach]

I've had a similar experience Frank, but it could be a completely different cause. My valve power amp was giving some almighty lightening-like cracks in the first few minutes after power up. I assumed it was a capacitor or something building a charge and letting go (I know nothing of the workings of these things and don't know if this is even possible!). Also there were low volume crackles and rustles that had me checking that the amp wasn't actually on fire, then eventually one of the KT88 valves died, I replaced it and the problem ended.

PS. What do you think of the Adele 21 quality? I'm finding it quite distorted and I hope it may be the copy as I like the album.

[Effem]

I've had a similar experience Frank, but it could be a completely different cause. My valve power amp was giving some almighty lightening-like cracks in the first few minutes after power up. I assumed it was a capacitor or something building a charge and letting go (I know nothing of the workings of these things and don't know if this is even possible!). Also there were low volume crackles and rustles that had me checking that the amp wasn't actually on fire, then eventually one of the KT88 valves died, I replaced it and the problem ended.

PS. What do you think of the Adele 21 quality? I'm finding it quite distorted and I hope it may be the copy as I like the album.

I have had valve amps in the past that popped, hissed, rustled and crackled, but this was a whole magnitude louder.

I did for one brief fleeting moment think it was the CD and it was supposed to be there, so I played it again and no bang ensued. Having said that, if it was purposely put there and I had the volume on "11" then gawd helps us all :mental:

Yes the SQ of the Adele 21 album isn't all that great. I also bought Imelda May's "Mayhem" and that really is dire :(

[GaryB]

My power amp did this a few years ago and it turned out to be the electrolytic capacitors that had 'dried out'. When they were removed, you could shake them and hear the internals wobbling about inside. I replaced all the electrolytics and it's been as good as gold since.

Looking into it further, I found that the electrolytics in my amp were actually rated far too close to their operating voltage and in some cases were below that. I replaced them with higher spec. parts.

[Effem]

My power amp did this a few years ago and it turned out to be the electrolytic capacitors that had 'dried out'. When they were removed, you could shake them and hear the internals wobbling about inside. I replaced all the electrolytics and it's been as good as gold since.

Looking into it further, I found that the electrolytics in my amp were actually rated far too close to their operating voltage and in some cases were below that. I replaced them with higher spec. parts.

This amp is brand new :eek:

Many moons ago when I was in the TV repair trade we used to put a big smoothing cap into a mains safeblock and slam it shut for some light entertainment on a rainy day :lol:

If a smoothing cap had gone bang then there would be electrolyte all over the boards and I can't see any signs of it.

[GaryB]

If a smoothing cap had gone bang then there would be electrolyte all over the boards and I can't see any signs of it.

Mine failed after several years of operation and there was no sign of electrolyte having leaked out. None of the caps had physically 'exploded' so I guess the electrolyte had somehow evaporated. If your amp is new then it does sound like a different problem.

[Mark Grant]

I had something similar happen a few years ago.

About 3 am we where woken by an almighty 'bang' similar to the noise of a very near lightning strike. :eek:

One of those noises in the night that makes your heart miss a beat :eek:

Went downstairs expecting some damage of some kind or a break in, nothing, everything as normal.

A few days later the same happened during the night.

Eventually traced to my subwoofer that I had at the time.

It was a faulty capacitor in the PSU that must have decide to leak something during the night. This was a powerful subwoofer :) very noisy when asleep :eek:

I now switch subwoofers of at the wall socket at night, not on standby.:)

-

[Effem]

I have sent an email off to Shaun at Audiosantum to see what he makes of it

[hifi_dave]

I can confirm that the recorded quality of the Adele 21 album is indeed, NAFF...:doh:

No idea about the 'crack' though.

[Effem]

Crikey that was quick.

Just got an email back from Shaun saying he has passed my email over to the tech guys at XTZ for their thoughts

[The Grand Wazoo]

I have a memory of an electronics lesson in Sixth Form at school, where we decided to investigate exactly why the teacher had sternly warned us to wire up capacitors with great care & to be sure they were not connected the wrong way. Someone connected two flying leads to one & wired the other ends into a mains plug, plugged it in, flicked the switch & dived behind a desk.
Kabooooom!! - windows shook, teenagers were temporarily deafened & the cane was liberally and repeatedly applied to various rear ends by the Deputy Headmaster!

[Effem]

Had a response from XTZ via Audiosanctum:

"Hm, the only thing I can think of that makes sense is if he runs the amp using digital inputs, and the DAC for some reason lost sync with the source signal. This can cause loud noises as the most significant bits of a data word are misinterpreted. If it happens again we can always replace the DAC. On the other hand, if he use the analog inputs this cannot happen really. (at least not without some nasty smoke coming out)"

[Butuz]

Irk that's a strange one!!

I guess that's what you get for trying to listen to Adelle. It probably wasn't the amp it was just god banging his head on the desk ;)

Butuz

[Alex_UK]

Presume you were using one of the digital inputs Frank? Guess that explanation is plausible - if you were.

[Effem]

As it happens, I was using it via the coax digi input.

I have had odd whistles, screeches and wails before out of systems that had lost the sync input, but this was a loud bang :scratch:

[Reid Malenfant]

If it lost the lock it's quite possible it could think you have a high input & then lock & go to DC quickly, this would make a loud bang as the thing possibly reset. The same is of course possible if it lost lock, sat at a DC (0V) level & then went high as it regained the lock...

I'd monitor the thing, if it happens again it might be worth having a new DAC fitted.

How long a coaxial lead are you using Frank?

[Effem]

How long a coaxial lead are you using Frank?

It's 1 metre long Mark, triple screened silver job

[Reid Malenfant]

That should give zero problems then :scratch: No idea why the hell it should lose lock...

[magiccarpetride]

Last night I switched on my system to warm up ready for my usual nightly listening sesh, put the kettle on for a cuppa, opened the package containing the new Adele album that arrived yesterday morning to give that a whirl in the CD player.

Played track number 1 fine, around 10 seconds into track 2 the speakers let out the biggest bang you could ever imagine AND I INSTANTLY BLEMISHED MY UNDERWEAR :( I stood there in total shock expecting a huge cloud of acrid smoke from either the amp or speakers - my ears were still ringing a minute later, but no signs of smoke, no smell of burning and the CD was happily playing away at the same low volume level I had it at. Amp was as warm as normal, sniffed around the vents and no telltale smells emanating from it, placed my finger gently on all the bass/mid cones and they were doing as they should be doing. Ear pressed to each tweeter - fine.

I am donald ducked if I know what on earth caused this massive bang. I didn't notice the lights dim or brighten (perhaps they did), the missus said the telly and lights in the lounge were fine. If it was a mains surge, the the Belkin PF30 should have caught that one would assume :scratch:

Any road up, despite much trepidation and nail biting, I listened to the rest of Adele at low volume, then played the whole of Yello's Baby and cranked the volume up halfway - was fine.

Are you sure you weren't able to smell anything after this incident?

[Marco]

Yes, shite.

Marco.

[Tim]

Yes, shite.

Marco.
:D

[Effem]

Are you sure you weren't able to smell anything after this incident?

I did say that I had blemished my underwear and it sure as heck wasn't smelling of Roses :D

[Marco]

S'ok, his nappy caught it ;)

Marco.

[anthonyTD]

It definately sounds like something arcing over, i would suspect something in the low signal end, either CD player, or Preamp, it was then amplified by the power amps hence the percieved volume of the Crack.
out of interest, you say you went to put the kettle on, did you notice the cracking sound just after the kettle switched off ?
if so, it could be that when you put the kettle on the mains dropped, and when it clicked off the mains went back up suddenly, is this a posibility ?
hope this helps.
Anthony,TD...

[Effem]

It definately sounds like something arcing over, i would suspect something in the low signal end, either CD player, or Preamp, it was then amplified by the power amps hence the percieved volume of the Crack.
out of interest, you say you went to put the kettle on, did you notice the cracking sound just after the kettle switched off ?
if so, it could be that when you put the kettle on the mains dropped, and when it clicked off the mains went back up suddenly, is this a posibility ?
hope this helps.
Anthony,TD...

The kettle had finished boiling long before I switched the system on and I was having a slurp on me cuppa as I was playing track one of the CD

[anthonyTD]

The kettle had finished boiling long before I switched the system on and I was having a slurp on me cuppa as I was playing track one of the CD
OK,
Are there any other high current items in the house that might have swiched on and off around that time ie; shower, emersion heater, electric fire, heater etc.
Anthony,TD...

[Effem]

OK,
Are there any other high current items in the house that might have swiched on and off around that time ie; shower, emersion heater, electric fire, heater etc.
Anthony,TD...

No nothing.

I also have the entire system plugged into a Belkin PF30 so I would expect that to capture any nasties of the mains.

[Marco]

Are you sure it wasn't just a pre-'panty pop', a mini explosion, a little chuff-ette, as it were (perhaps due to over-excitement at how wonderful your system was sounding), before the full-on soiling happened? :eyebrows:

Marco.

[Effem]

Are you sure it wasn't just a pre-'panty pop', a mini explosion, a little chuff-ette, as it were (perhaps due to over-excitement at how wonderful your system was sounding), before the full-on soiling happened? :eyebrows:

Marco.

Well if it happens again Marco I am going to plumb the washing machine in my listening room to save running to the utility room :eyebrows:

[Haselsh1]

Just to add my bit on the sound quality issue; I had no intention of buying the second Adele album on the grounds that the first one was so bad. There were moments on the first album when I worried for the safety of my then Dali speakers as the treble completely broke up. Really not good.

[anthonyTD]

As for the Adele song that has been playing non stop recently, i cant stand it!
I know she has won awards etc, but i just wish she would leave the guy alone and just get on with here life,GET IT, he's with someone else stop wining on, and on, and...!:lolsign:
Anthony,TD...

[audiosanctum]

Is it still running ok now Frank?

[Effem]

So far so good Shaun. Thanks for your speedy assistance :)

[The Black Adder]

I'm sure this won't happen to you guys but a year ago or so my previous set up (transistor) let out a very loud 'WEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE - BANG....Phhhhhhhhh WOOOOOOOOOOOUGH!"

Seconds later my right speaker was on fire, the amps were melting away and the room was half full of toxic fumes. A nice pair of Wilson Benesch's up the spout and NVA amps boiled to an inch of their lives.

The fire alarm saved us as it was 1am in the morning... if you don't already have one... BUY ONE!

http://i457.photobucket.com/albums/qq295/musical_submarine/WB/ResizeofDSC03177.jpg http://i457.photobucket.com/albums/qq295/musical_submarine/WB/ResizeofDSC03165.jpg

Turn your shit off at night - Lesson learned.

[Reid Malenfant]

:eek: Bloody hell! I have never seen anything like that before :eek:

[The Black Adder]

Yeah.. it was pretty bad and it took months for the insurance to pay out for new carpets and a re-paint of the room.

It was amazing in regards to how much smoke there was, horrid toxic smoke too, it took weeks for it to fully go away.

[Effem]

Did you ever find out what caused it Joe?

[Lodgesound]

.....an abject lesson in why you build protection circuits into amplifiers........they are extremely dangerous under certain fault conditions...

[Reid Malenfant]

.....an abject lesson in why you build protection circuits into amplifiers........they are extremely dangerous under certain fault conditions...
Exactly, no loudspeaker can self destruct & catch fire without some signal from an amplifier!

[Lodgesound]

....indeed Sir.....how on EARTH did the output fuses not blow or protection circuits not operate???

[WOStantonCS100]

Scary stuff...

I've usually heard of this happening with folks who run music from their PCs where losing lock seems to more common due to software, sometimes possible even when things are configured rather meticulously. At least the inside of your amp didn't look like this! (see below) Ought not have your hands in there when it lets go. :eek:

http://i815.photobucket.com/albums/zz80/TCKA1ESa/Projects/explodedjtm45cap.jpg

ABOVE: Exploded cap inside a vintage JTM45 guitar amp

[The Black Adder]

Did you ever find out what caused it Joe?

Well Frank, after further investigation it was most definately the amplifier.

Saying that, with CE safty rules I'd expect all manufacturers of loudspeakers to now use different materials for speaker cones or at least coat them with some kind of flame retardent I know this was a rare incident and I hope it never happens to anyone else but safty rules should come first me thinks.

[The Black Adder]

.....an abject lesson in why you build protection circuits into amplifiers........they are extremely dangerous under certain fault conditions...

Yep.. Well, NVA don't not have these protection circuits but should have even if it sits on the sound slightly... it's a no brainer.

And if you leave your stuff on 24/7 I'd seriously consider not doing... for the amount of difference in the sound it's really not worth it.

If the sound is really that bad not being left on then in my opinion I'd buy somthing else.

Chord have a very good system inside their amps which turns off the output circuits all together whilst on standby, I guess sound studios would sue the crap out of them if they caught fire whilst un attended.

[The Black Adder]

I've got some pics of inside the amps.. I'll dig them out

[The Grand Wazoo]

Mark, if I was a NS1000 driver owner, I'd be rather worried to see a thing like that.

Beryllium does not burn easily in air but if involved in a fire at high temperature (say > 8OO°C) then it will rapidly oxidise and the oxide may contaminate the atmosphere, building and equipment. Beryllium burns easily in air when finely divided or as massive metal in pure oxygen or in oxygen enriched atmospheres. Beryllium alloys also may be disseminated in a fire and contaminate buildings and equipment to above the recognised limit of 0.1 mg/m2 of beryllium at which a cleaning operation must be carried out.

(From: http://lhc-proj-qawg.web.cern.ch/lhc-proj-qawg/CD-ROM/Safety/IS25.pdf )

[Reid Malenfant]

Indeed, i know the stuff is extremely hazardous Chris & it's one of the only substances that the lungs simply can't deal with. However, i always switch off the power amplifiers after use. Obviously that doesn't prevent something else somewhere in the house from catching fire though :rolleyes: It hasn't happened yet & fingers crossed it never will :)

I think i'm more worried about the fridge exploding due to the gas they use these days (it has been known to happen if there is a leak) :eek:

[Garfed]

After several years of operation of the mine did not, there are no signs of electrolyte leakage. There was no body cover 'explosion', so I guess somehow lost electrolytes. If your amp is new, then it is like the sound of a different problem...

[Techno Commander]

Thats quite impressive (in a bad way). I have seen pro drivers mashed to within an inch of their lives, but nothing like that.

[Reid Malenfant]

I've got some pics of inside the amps.. I'll dig them out
Did you ever find the pics of the interior of the amps Joe?

I honestly still can't get over the destruction of that speaker :mental: You just want to be glad you had a fire alarm installed or it might have been much more serious :eek:

[spendorman]

Many years ago my Quad preamp went BANG after switching on. All kept working though.

On inspection found the mains suppressor had exploded. A new one was ordered from Quad.

[Dr Bunsen Honeydew]

Did you ever find the pics of the interior of the amps Joe?

I honestly still can't get over the destruction of that speaker :mental: You just want to be glad you had a fire alarm installed or it might have been much more serious :eek:
Quite simple. He has a photo of the voice coil that shows where the over heating originated before the voice coil burnt out. It shows a clear hot spot as the former is burnt through at that point. When this happens with a high power voice coil the insulation vaporises before the wire fuses and creates a progressive short across the voice coil, which in turn takes out the amp. Now about 80% of the time the output devices on the amp will go open circuit, which just means a repair. But sometimes they fuse closed and put the DC rail down the voltage line. When blipped on when the amp came back there was no DC on the output, the device had fused open circuit, but I think there must have been DC present for some of the time otherwise the burn out of the voice coil wouldn't have been so extensive, unless it was heat created by the fire.

The fire was caused by a progressive short in the voice coil, which caused the amp to blow and causing the heat from the voice coil to set fire to the speaker wadding and to the melt the speaker cone.

These are speaker faults both in faulty part, the voice coil, and faulty design to use flammable products in loudspeaker manufacture. In over 30 year of producing amplifiers and speakers I have never seen anything like this.

That was my report I put through to the insurers, who after their usual performance of trying to avoid it, paid out.

To be safe the owner wont use either product involved again and I don't blame him, in his situation I would do the same.

Regarding photos of the inside of the amp you will see some resistors burnt out, one small cap popped, and the smoke damage of that. Nothing would get outside the amp but a very small amount of smoke / fumes from the lacquer burning off the resistors.

[Reid Malenfant]

All very nice Richard, but what i'm saying is that the voicecoil will not burn out without power being fed to it & the only place it can get that from is the amplifier.

Do you know of another place? If so please fill me in :)

So Joe goes to bed after a listening session & unfortunately leaves the power amps switched on... They aren't being fed a signal as he has finished listening to music for the day :)

So all should be well but obviously it wasn't to be, for some strange reason a signal appeared that produced a good deal of power, enough to fry the voicecoils of a rather expensive pair of loadspeakers :doh:

So lets have a good think here, no signal into the amp so how come it can output one? Either it went unstable or there was a collector/emitter short due to ageing or thermal stress (silicon/copper interface breaking down in the transistor). If it was due to instability i'd expect a rather buggered tweeter. So it was probably a collector/emitter short & the amp supplied DC to the speaker.

Why no output fuse? Why no current limiting? Why no crowbar to blow fuses on the DC lines?

Just a thought..

[Dr Bunsen Honeydew]

Are you incapable of reading English, or do you just want a fight?

The sequence is explained perfectly. The relevant point is that a short circuit on the voice coil overheated the amp which obviously then popped its output stage and put DC down the speaker line. You can get the report from the insurers as they have to hold it on file in case it leads to a court case, it didn't. The court case would have been because a speaker manufacturer is using inflammable material in places that contravene safety regs, that is the reason the speaker caught fire, nothing else. I have amps go DC at least a couple of times a year and neither the amp or the speaker have caught fire in any such case but this one and nor should they.

Now I know you want to run diversion to take away the post aimed at DSJR, but why are you being his keeper, why do you wish to have a fight with me.

[Dr Bunsen Honeydew]

This getting boring, so now you edit the post to add other ignorant claim.

"So it was probably a collector/emitter short & the amp supplied DC to the speaker.

Why no output fuse? Why no current limiting? Why no crowbar to blow fuses on the DC lines?"

Because they mess up the sound of the amp, and there are very few times they cause problems not being there, as when a customers wife unplugged the speakers and dropped the cables on the floor and hoovered over the top of them behind the speakers and short circuited both channels and then plugged the cables back in.

Did it cause a speaker fire, no. One channel of the amp failed open circuit one failed closed circuit, so even though it wasn't our fault we did a deal with the speaker company so the guy wasn't stitched up the way you usual are over repairs and fitted a new bass driver for him and we repaired the amp free of charge even though it was five years old. That I think was the funniest one I remember.

Do you actually understand what a fuse is? and what it means to fuse. It is not only a bit of glass with a thin wire in it, it can be anything, all it is is the first thing that goes open circuit on failure. In this case the emitter resistors act as the fuse.

[Reid Malenfant]

Richard, i don't stick up for anyone but myself.

The thing is is this though. Joe was listening to his system before he went to bed & it was obviously ok. Now maybe it did have a 'hot spot' on the voicecoil which may well have shorted a few turns. Ok so it's now a DC resistance of 3.4 instead of 3.7 ohms. AC impedance might a very badly off & i'd expect that a shorted turn in a voicecoil will mess things up totally whilst being fed with an AC signal, but it was ok whilst listening to music or Joe would have quickly shut it down & not left it switched on. Transformer short circuits do much the same. Ok with no signal but feed it one & you are in the crap :eek:

I'd have expected vastly more damage to have been done with a few Watts RMS whilst listening than an amplifier doing bugger all...

So i can't accept what you say, simples :)

No fight as you call it, i feel you are the one getting upset as i certain am not. It's simply that i cannot accept the version of the events that have been portrayed.

Like i said already, where was the output fuse or the current limiting or the crowbar to blow fuses in the DC lines in the event of a fault?

[Dr Bunsen Honeydew]

I have answered all of this in previous posts, So either you are incapable of reading it, or you do not wish to, or you wish to create and prolong a conflict. Well in either of these cases I am afraid you can just play with yourself.

[Reid Malenfant]

I have answered all of this in previous posts, So either you are incapable of reading it, or you do not wish to, or you wish to create and prolong a conflict. Well in either of these cases I am afraid you can just play with yourself.
Fine :)

[Marco]

Ok, guys, I've let this one run for a while, but it's time to let it go now and change the record - cheers! :cool:

Marco.

[DSJR]

I think that in this day and age, and with the usually more capable components available now, that audio products shouldn't need to be left on 24/7. I think this ruse was used as an excuse of cheap components, drifting quiescents and inadequate thought on the part of a particular amp manufacturer back in the bad old days of the 80's.

[AlexM]

Going back to Effem's original issue, I wouldn't have thought that loss of sync would lead to an output significantly higher in volume than that set by the volume control, i.e. you may get a nasty noise which could be loud, but it wouldn't be higher than 0Db level signal on the source.

I would guess therefore that the amplifier had a transient fault, and that the manufacturer's explanation doesn't hold water. I also haven't experienced any very large bangs as a result of mains-bourne interference or glitches - these are more of a quiet 'tick' or 'pop' for me..

I'd look for a warranty repair or replacement if I were you..

Regards,
Alex

[Dr Bunsen Honeydew]

I think that in this day and age, and with the usually more capable components available now, that audio products shouldn't need to be left on 24/7. I think this ruse was used as an excuse of cheap components, drifting quiescents and inadequate thought on the part of a particular amp manufacturer back in the bad old days of the 80's.
Nonsense, and provable to anyone who wants to hear it.

If an amplifier is incapable of resolving information to high enough level then it is up pretty quickly, but with a good amp you are probably waiting half an hour or more for it to come up, do you want that, most peoples listening sessions don't last for more than an hour, so half the time is spent not hearing the true potential of your system. Regarding components you are arse about face, old passive components (which are the ones causing these changes) made pre 1970 are better than than those made pre 1990 which are better than those made now. The difference now is size and to a degree consistency and longivity and cheapness of manufacture, nothing more. Quiescent current drifts with temperature, nothing more, and makes not a blind bit of bloody difference to the sound of an amplifier, within acceptable parameters, all it does is offset the the voltage swing slightly. But the DC offset is useful when the system is on but out of use by providing a constant minute current across the voice coil, which again makes an audible difference as it keeps the coil formed internally and also keeps the crossover caps active. Only music can loosen up the spider and the surround of a drive unit (a bit like tenderising a steak) which is why speakers need a track or two to come on song.

So there are very strong arguments for leaving a system powered up. With valve amps not so much so as they come up more quickly due to the voltages involved and often cost a lot in electricity to keep powered up, and also valves are finite beasts that go down over time of usage, where as transistors don't, they go down according to the number of times they are stressed with switch-on.

[Yomanze]

I don't have old caps etc. that might make the effect more pronounced, but there is definitely a big difference between listening to my Exposure amp "cold" vs. left on. The sound becomes more liquid and refined if it's nicely warmed up. In fact the other day Carly put some tunes on & it didn't take me long to comment: "did you switch the amp off last night?".

[AlexM]

In terms of warm-up, I think it isn't too hard to switch on the kit 30mins or so before a listening session and that this is too much of a sacrifice to be environmentally friendly. I think leaving any electrical appliance powered up when unused and unattended is wasteful and will shorten it's working life, and following Joe's horror show earlier in this thread, potentially dangerous!.

My kit is all hollow-state, so leaving it powered up isn't really an option anyway if I want a realistic service life from my valves.

Regards,
Alex

[Dr Bunsen Honeydew]

More nonsense. It was nothing to do with the system being left on, it was caused by a faulty bass driver with a short circuit on its voice coil.

[Marco]

I think Alex was just making a general point, Richard, and not necessarily referring to the previous argument :)

Marco.

[AlexM]

Marco - Just so...

Richard - no need to be antagonistic. I wasn't referring to Joe's issue, simply making a point that equipment can fault at any time, sometimes with safety consequences and it is best not to leave things powered up when unattended for this reason.

[roob]

Oh dear it's starting ;)

[Butuz]

Personally I think leaving the system on 24/7 is a ridiculous idea. I mean you don't leave your car on 24/7 because it runs better when its warmed up do you?

Personally I think anything that takes more than 30 mins to warm up is poorly designed in some way. My PC is cold when I switch it on but it works at 100% effectiveness and at 100% speed from the moment I turn it on regardless if the ambient is 10 degrees or 30 degrees. A PC is orders of magnitude more complicated than an amplifier electrically

Butuz

[worthingpagan]

I used to leave to leave my kit on, till one day an old Luxman amp I had started to make a buzzing noise :scratch: Spoke to a techie friend who swore blind that all I was doing by leaving kit switched on was drying out the caps quicker. He also stated that "solid state" did not need warm up time like valves used to, they are ready to use from the off (don't shoot, i'm only the messenger) :sofa: Don't think it makes much difference with the budget kit I listen to nowadays and definately don't think it makes any difference at all to Lemmy & friends :band:

[Audioman]

Because it takes 30 mins to warm up doesn't mean the design is poor. If it takes several hours I would agree. I do agree that leaving everything on 24/7 is ridiculous and that with power amps there may be a slight risk. However a risk I wouldn't present to an insurance company as a get out. The exception is solid state phono stages which are low power and safe to leave on with the greatest benefit to sound.

If you switch on your hi-fi from cold and are a vinyl user it will take one side of an LP for the stylus to warm up to optimum performance (20 mins) and nearly as long for speaker cones to loosen up. By then your amp should be close to warming up. Best idea is to switch everything on and go make a cuppa (or something stronger) before commencing a listening session. It will still take approx an Lp side to approach optimum sound. :cool:

[WOStantonCS100]

Personally I think leaving the system on 24/7 is a ridiculous idea. I mean you don't leave your car on 24/7 because it runs better when its warmed up do you?

Personally I think anything that takes more than 30 mins to warm up is poorly designed in some way. My PC is cold when I switch it on but it works at 100% effectiveness and at 100% speed from the moment I turn it on regardless if the ambient is 10 degrees or 30 degrees. A PC is orders of magnitude more complicated than an amplifier electrically

Butuz

After all, what's heat to a thermionic valve... ;) Yes, I agree over 30 minutes is a bit too long for a "warm up". However, all the valve amps I have seem to be "settled in" when they're good and warm and that may be longer than 30 minutes. Besides... my PC sounds like crap... even when it's warmed up.

[Marco]

The only components I have in my system that are solid-state are my CDP, DAC, and the PSU for my T/T, and those are left switched on 24/7. The DAC, in particular, sounds pants for about 2 hours after switch on, if it's been switched off for any longer than 10 mins. I ain't waiting that long for my music to sound right.

I also take the view that the internal components actually age LESS when left in use. It's the continual on>off>on>off cycle that's actually worse.

After all, most equipment failure occurs during switch-on, due to the stress impacted on the circuitry via the initial electrical surge. Therefore, the less that kit is switched on (after being switched off), and subjected to that initial surge, the better! ;)

To take a simplistic view, how many light bulbs have you seen fail, due to being permanently illuminated? They usually go pop after you've flicked the light switch on...... Think about it.

No way do I leave my valve amps on though, for three main reasons:

1) Valves can be rather volatile beasts - and so are major potential fire hazards if left permanently switched on.

2) My power amp operates in pure Class A, and therefore the running costs would be horrendous.

3) It would drastically reduce valve life, especially considering that I mostly prefer using expensive NOS valves, and thus want them to last for as long as possible!

When switched on my amps are up to speed, sonically, in around 20 mins - so it's no real hardship to switch them off every night.

Marco.

[Alex_UK]

To take a simplistic view, how many light bulbs have you seen fail, due to being permanently left lit? They usually go pop after you've flicked the light switch on...... Think about it.

That's exactly the analogy I've used - rightly or wrongly - to justify leaving my kit on 24/7. I've done this for the last 15+ years, I'd much rather my kit is ready for action whenever I get the chance to listen.

[Marco]

Always best being 'primed and ready for action', eh big boy? :lol:

:booty:

Marco.

[Dr Bunsen Honeydew]

Just because we use the expression warm up doesn't mean the process has anything to do with heat. Sometimes it does such as with a TT stylus.

I don't fully understand the process but I will throw experience at you. The bigger and more complex the power supply then the longer it takes. An AP10 will take about 2 days to sing to the point you don't detect change from new, and it will take about 20mins to come on song if having been off for a day. Where as a TDS will take over a month to fully stop getting better from new, and will take the same amount of time to come up to full potential as it has been off.

Major difference is AP10 has 30va PSU for the whole circuit. TDS has 1000va for the output stage, 750va for the driver stage, 500va for the pre driver / current mirror and 300va for the input stage.

The interesting thing is that from switch on the amps sound very similar, after 10 minutes they are different beasts. The process is logarithmic, in other words the biggest change is in the first minute and then the curve of change diminishes until it becomes inaudible. I believe change at a minute level is still going on but it has dropped below the ability of the system to resolve it. I think of a system as a window to your music and windows get dirty or have distorted glass, if so then small detailed changes in your view get blocked or changed, same with musical information.

[Butuz]

To take a simplistic view, how many light bulbs have you seen fail, due to being permanently illuminated? They usually go pop after you've flicked the light switch on...... Think about it.

No way do I leave my valve amps on though, for three main reasons:

3) It would drastically reduce valve life, especially considering that I mostly prefer using expensive NOS valves, and thus want them to last for as long as possible!

:scratch::scratch::scratch::scratch: Surely valves have more in common with lightbulbs than solid state integrated circuits do?

So shouldn't you be leaving your valve amps on in order to prolong life??? Or should you be turning your lightbulbs off to prolong life??

I am confused now :D

Butuz

[Dr Bunsen Honeydew]

A valve is not a light bulb, the same as window is not the same as a bottle even though they are all made of glass.

[Butuz]

No but it sure turns electricity into light and heat pretty good..

Butuz

[AlexM]

valves age and loose emission, out-gas and generally age with use, so better to listen to music with them than just heat the
room!

[Thing Fish]

A valve is not a light bulb, the same as window is not the same as a bottle even though they are all made of glass.

But surely what a glass is to a bottle is what a bottle is to a valve therefore a valve is to a light bulb what a valve is to a bottle. Where the window comes in feck only knows...?

[WOStantonCS100]

But surely what a glass is to a bottle is what a bottle is to a valve therefore a valve is to a light bulb what a valve is to a bottle. Where the window comes in feck only knows...?

:lolsign::lolsign:

[cuddles]

http://i106.photobucket.com/albums/m262/mumblescuddles/glassbottle-1.jpg

BOTTLE GLASS GLASS BOTTLE

:lol:

[Marco]

valves age and loose emission, out-gas and generally age with use, so better to listen to music with them than just heat the
room!

Indeed.

I suppose there is an argument to say that valves also don't 'like' being switched on and off, the same as light bulbs, for similar reasons, but this is outweighed by the fact that they lose emission and generally wear out with use, thus adversely affecting their sonic performance and reliability - and that replacing them costs considerably more than replacing light bulbs! ;)

Marco.

[Dr Bunsen Honeydew]

Anything electrical or electronic can have problems, My sister had a hoover catch fire. But specifically audio the one I remember most vividly is sitting having a cuppa in the original shop of Hi-Fi Consultants in Peterborough right at the end of my time with AR as I had done some freelance work on a couple of speaker designs for them. We were listening to the first valve amp to emerge after about 15 - 20 years of non production in the UK, it was the Michaelson & Austin TVA1, well for no apparent reason while playing music it decided to catch fire and set fire to the carpet, my cup of tea put out the carpet. OTL valve amps were also notorious for catching fire and one did famously burn a house down in the USA.

But as I say *any* industry that involves using mains electricity has stories like this - shit happens very occasionally. I had a friend who I played cricket with when living up in Leicestershire, who was head fire officer for Leicester. He had some incredibly gory stories about the things he had seen, but he also always moaned about our ring main system which he said was a major cause of house fires, he said we would be much safer sticking to a radial system.

[Marco]

Indeed, Richard.

I think you'll also find that smoking, chip pans, or things like Christmas tree lights being left on unattended, statistically cause way more fires than any hi-fi equipment! ;)

Marco.

[spendorman]

I suppose that I had an incident that could have been much more serious, if it was not for the 2A fuse in my B&W DM5 speakers.

Music was playing at quite low level (Radford ZD50 and B&W DM5) and I noticed that one channel had stopped working.

The ZD50 had some some reason put out very heavy DC on one channel. This blew the DM5 2A fuse.

The ZD50 has protection circuits too, but they must have failed.

Anyway, I happy that the speaker was saved by the fuse. I suppose that the fuse reduced the chance of a fire as well. Just as well as the ZD50 has a massive power supply.

[AlexM]

Yes, almost anything can fail in unanticipated ways. My Bosch kettle almost stated a fire when the thermostat or switch failed and it spontaneously switched on, boiled dry and melted down!.

As you say, s**t happens sometimes!.

[Dr Bunsen Honeydew]

I suppose that I had an incident that could have been much more serious, if it was not for the 2A fuse in my B&W DM5 speakers.

Music was playing at quite low level (Radford ZD50 and B&W DM5) and I noticed that one channel had stopped working.

The ZD50 had some some reason put out very heavy DC on one channel. This blew the DM5 2A fuse.

The ZD50 has protection circuits too, but they must have failed.

Anyway, I happy that the speaker was saved by the fuse. I suppose that the fuse reduced the chance of a fire as well. Just as well as the ZD50 has a massive power supply.
The problem is that 2amp fuse is really screwing up the sound of that speaker. As I said before a fuse doesn't have to be glass with a bit of wire in it, a fuse is the first thing that burns out in a overloaded circuit. In your case without the fuse it would probably be the voice coil in your bass speaker, which would have been expensive. BUT the thing that never should happen is for the fusing of that voice coil to set fire to the wadding and loudspeaker cone, that is plain and simply bad and dangerous design. Both by EU and UK safety regs and laws they should both be either non flammable or fire resistant, as with furniture regs about being set on fire by a cigarette.

[spendorman]

Yes, almost anything can fail in unanticipated ways. My Bosch kettle almost stated a fire when the thermostat or switch failed and it spontaneously switched on, boiled dry and melted down!.

As you say, s**t happens sometimes!.

Now that should not have happened. Going back 25 years or so, I worked developing domestic electrical appliances and kettles was one of them.

There should be reliable protection in the actual element.

I remember engineers playing a trick on the development manager. they put a sample of the newly developed plastic electric kettle in an industrial oven, just long enough for it to collapse.

This was left on the bench for him to find.

When he did, not surprisingly, he looked very worried. He must have thought that it was a serious failure.

Someone soon put him straight and he had a good laugh.

This was at Sunbeam/ Rowenta.

[spendorman]

The problem is that 2amp fuse is really screwing up the sound of that speaker. As I said before a fuse doesn't have to be glass with a bit of wire in it, a fuse is the first thing that burns out in a overloaded circuit. In your case without the fuse it would probably be the voice coil in your bass speaker, which would have been expensive. BUT the thing that never should happen is for the fusing of that voice coil to set fire to the wadding and loudspeaker cone, that is plain and simply bad and dangerous design. Both by EU and UK safety regs and laws they should both be either non flammable or fire resistant, as with furniture regs about being set on fire by a cigarette.

Well, yes, I understand that fuses may have a small effect on the sound, but one has to weigh up the pro's and con's.

In a late 70's test, the DM5's (with their 2A) fuse still managed to come higher in sound quality than most speakers that did not have fuses. Strangely, the top loudspeaker in that test was the JR149 that also has fuses in.

Both these speaker beat things like Spendor BC1's

[Rare Bird]

I would rather have protection. Ballerkz to any so called sound detriment, my speakers don't have fused crossovers at the mo but they will be getting them well a minature circuit breaker that is.

[DSJR]

Nonsense, and provable to anyone who wants to hear it.

If an amplifier is incapable of resolving information to high enough level then it is up pretty quickly, but with a good amp you are probably waiting half an hour or more for it to come up, do you want that, most peoples listening sessions don't last for more than an hour, so half the time is spent not hearing the true potential of your system. Regarding components you are arse about face, old passive components (which are the ones causing these changes) made pre 1970 are better than than those made pre 1990 which are better than those made now. The difference now is size and to a degree consistency and longivity and cheapness of manufacture, nothing more. Quiescent current drifts with temperature, nothing more, and makes not a blind bit of bloody difference to the sound of an amplifier, within acceptable parameters, all it does is offset the the voltage swing slightly. But the DC offset is useful when the system is on but out of use by providing a constant minute current across the voice coil, which again makes an audible difference as it keeps the coil formed internally and also keeps the crossover caps active. Only music can loosen up the spider and the surround of a drive unit (a bit like tenderising a steak) which is why speakers need a track or two to come on song.

So there are very strong arguments for leaving a system powered up. With valve amps not so much so as they come up more quickly due to the voltages involved and often cost a lot in electricity to keep powered up, and also valves are finite beasts that go down over time of usage, where as transistors don't, they go down according to the number of times they are stressed with switch-on.

I have to disagree, but then, I don't have an agenda here.

Modern transistors, especially output ones are far more capable than most used in audio twenty to thirty years ago and I'm informed also that capacitors are performing better and longer lasting too - compared to the rubbish used in UK made gear back then. The fact that the resistors used today would have been regarded as luxury items in the 70's as well, kind of supports this I feel.

If my "HiFi" was so "revealing" that it needed to be left on all the time and that I had to sit on the edge of my seat to listen to it, I'd have binned it decades ago - I did in fact, but ended up with something even better :)

[Dr Bunsen Honeydew]

I have to disagree, but then, I don't have an agenda here.

Modern transistors, especially output ones are far more capable than most used in audio twenty to thirty years ago and I'm informed also that capacitors are better and longer lasting too. The fact that the resistors used today would have been regarded as luxury items in the 70's as well, kind of supports this I feel.

If my "HiFi" was so "revealing" that it needed to be left on all the time and that I had to sit on the edge of my seat to listen to it, I'd have binned it decades ago - I did in fact, but ended up with something even better :)
Simply not true, how do you come to these conclusions do you make or design gear, have you used and compared components over that time period. well I have!

Transistors have changed very little in 30 years. The major changes were in the 60's and early 70's. The change from germanium to silicon was large. The availability of high current Darlington long tailed pairs in the early 70's was major as well (which along with the invention of toroid transformers by Avel Lindberg created Naim products). Since then nought of importance apart from production moving to the far east and becoming cheaper. Ah! also the intro of power fets (if you like them) was another late 70's thing. All the progress in the 80's 90's and 00's has been in encapsulation.

Passive components in the 50's and 60's were *far* better sonically than they are now. Paper in oil caps are still by far the best sounding in big caps and polystyrene in small, but paper in oil is not practical in solid state amps due to size, and polystyrene cannot be used due to flow soldering machines now used for PCB production (they melt). Resistor are now produced with less pure oxides due to the Chinese cheapening things, terminations are now steel instead of tin plated copper. Transformers and coils made in the far east use less pure copper in the windings largely scrap reclaim, plates are of inferior steel with rust built in because they often come from scrap. Electrolytics are not so good now due to termination and plate quality, but are now smaller for reasonable quality

I can tell you from personal experience it is a struggle now to get components to the standard you need for good audio performance and a lot of my time is now spent sourcing them, often from new old stock. The thing that has interfered the most is the intro of CE regs and the other damn fool bureaucracy that has been imposed on us, and the removal of the use of lead tin solder from use hasn't helped either.

Once again I am sorry but you are talking out of your hat. For simple electronics or for things not built for something so resolving as musical quality then components are better because they are smaller and cheaper. But for us trying to create a product that reproducing a highly delicate art form it has made the problem far worse and is a constant struggle to maintain standards.

[Dr Bunsen Honeydew]

I would rather have protection. Ballerkz to any so called sound detriment, my speakers don't have fused crossovers at the mo but they will be getting them well a minature circuit breaker that is.
The sound detriment is not small. Obviously depending on how good the gear is in the first place. Put crap through crap and you don't hear it is crap you think it is normal!

[Marco]

If my "HiFi" was so "revealing" that it needed to be left on all the time and that I had to sit on the edge of my seat to listen to it, I'd have binned it decades ago

Sorry, Dave, I don't understand your logic... Revealing is precisely what you want, if you have any notions of achieving high-fidelity with your audio system. What would you rather have instead - a quagmire of coloration?

Sometimes I think folk are just playing at it and kidding on that they're a genuine hi-fi enthusiast, as well as being a music lover.

Yes, the latter is ultimately the most important, but if you're going to pretend to also being the former - then at least provide some convincing evidence....! ;)

Marco.

[WOStantonCS100]

Simply not true, how do you come to these conclusions do you make or design gear, have you used and compared components over that time period. well I have!

Transistors have changed very little in 30 years. The major changes were in the 60's and early 70's. The change from germanium to silicon was large. The availability of high current Darlington long tailed pairs in the early 70's was major as well (which along with the invention of toroid transformers by Avel Lindberg created Naim products). Since then nought of importance apart from production moving to the far east and becoming cheaper. Ah! also the intro of power fets (if you like them) was another late 70's thing. All the progress in the 80's 90's and 00's has been in encapsulation.

Passive components in the 50's and 60's were *far* better sonically than they are now. Paper in oil caps are still by far the best sounding in big caps and polystyrene in small, but paper in oil is not practical in solid state amps due to size, and polystyrene cannot be used due to flow soldering machines now used for PCB production (they melt). Resistor are now produced with less pure oxides due to the Chinese cheapening things, terminations are now steel instead of tin plated copper. Transformers and coils made in the far east use less pure copper in the windings largely scrap reclaim, plates are of inferior steel with rust built in because they often come from scrap. Electrolytics are not so good now due to termination and plate quality, but are now smaller for reasonable quality

I can tell you from personal experience it is a struggle now to get components to the standard you need for good audio performance and a lot of my time is now spent sourcing them, often from new old stock. The thing that has interfered the most is the intro of CE regs and the other damn fool bureaucracy that has been imposed on us, and the removal of the use of lead tin solder from use hasn't helped either.

Once again I am sorry but you are talking out of your hat. For simple electronics or for things not built for something so resolving as musical quality then components are better because they are smaller and cheaper. But for us trying to create a product that reproducing a highly delicate art form it has made the problem far worse and is a constant struggle to maintain standards.

I would imagine this sounds like a rant to some. However, when you actually start building amps and sourcing parts for them, the reality of many of the things just stated become glaringly obvious and annoying. On a very, very, very small scale this situation has spawned some specialists who provide as close to old school production of capacitors as possible. When you can get them, they are quite expensive.

[Marco]

Transistors have changed very little in 30 years. The major changes were in the 60's and early 70's. The change from germanium to silicon was large. The availability of high current Darlington long tailed pairs in the early 70's was major as well (which along with the invention of toroid transformers by Avel Lindberg created Naim products). Since then nought of importance apart from production moving to the far east and becoming cheaper. Ah! also the intro of power fets (if you like them) was another late 70's thing. All the progress in the 80's 90's and 00's has been in encapsulation.


That's kind also my understanding, Richard, although I've had some excellent results with metal-film resistors in my Croft preamp, which I guess are a modern invention.


Passive components in the 50's and 60's were *far* better sonically than they are now. Paper in oil caps are still by far the best sounding in big caps and polystyrene in small...


I think much depends on how the equipment is voiced that they're been put in. Again, electricial suitability aside, it's about sonic synergy.

I've tried paper-in-oils in both the crossovers in my Tannoys, and as coupling caps in my preamp, and took them out nearly as quickly as they were put in, as they smoothed and slowed the the sound down too much, and so were replaced with high-quality polys (Clarity Cap MRs) and teflon-film types from SCR, respectively, which were to my ears much more open, detailed and 'faster' sounding.

Perhaps results are different with valve amps?

However, I also know that paper-in-oils, in the right application can sound magical. It's just my experience to date has shown that I generally prefer quality polypropylene caps. For me, they tend to have less of a 'signature' - but that's ONLY based on the equipment I've used so far.


Electrolytics are not so good now due to termination and plate quality, but are now smaller for reasonable quality...


Again, experience so far tells me that I prefer quality polypropylene caps to most electrolytic types, for the same reasons as I explained about paper-in-oils. For me, however, there is no automatic 'best' - it's all application and interface dependent. One must also voice by ear accordingly in the final scenario.


I can tell you from personal experience it is a struggle now to get components to the standard you need for good audio performance and a lot of my time is now spent sourcing them, often from new old stock. The thing that has interfered the most is the intro of CE regs and the other damn fool bureaucracy that has been imposed on us, and the removal of the use of lead tin solder from use hasn't helped either.


Totally agree! If there's one thing I can't stand is pointless red tape and bureaucracy!! The no-life muppets, who sit on their fat arses in offices all day, dreaming up how to make life the most difficult for everyone else, need a damn good slap! :steam:


But for us trying to create a product that reproducing a highly delicate art form it has made the problem far worse and is a constant struggle to maintain standards.

I wish that more audio designers looked upon audio as a "highly delicate art form" (I totally agree), and didn't merely see it as a soulless 'black & white' entity for which current science has all the answers, and thus miss so much that's relevant in the process.... :rolleyes:

Marco.

[Lodgesound]

Very interesting read this thread with some very valid points.

In terms of resolution I have no doubt that some of the amplifier designs referred to here are an audible marvel of resolution.

What I think would disappoint folk here greatly is the equipment and the quality thereof that some of these recordings that we buy are made on.

Having worked in studio and high-end post production environments for some years (I don't anymore as I'm far too old to be of any use and cannot survive on the minimum wage) I can vouch for the fact that much of the equipment is built to a very high standard but nowhere even approaching the quality of some of the machinery used by members of this forum and designed / built by Richard.

Modern recordings are to a very large extent pretty awful sounding and "mastered" (I use the term loosely) by 18 year olds "so that they sound like really like loud yeah..." You only have to rip one of the tracks of your favourite CD into your favourite wave editing package to see how compressed and hideous some recordings are - even the ones perporting to be "high end".

Oddly enough some of the highest quality sound available to the domestic end-user is present on Blu-Ray discs of feature films. Feature film sound has for a long time escaped music industry and studio idiots largely because so much money is thrown at it along with the huge complexity of mixing and producing it. Small insights into this kind of quality can be heard if one listens to film music scores which are often recorded with a massive dynamic range for insertion in the feature itself. This has led to the rather odd phenomenon of absolutely full range soundtracks being present on Blu-Ray titles. If correctly decoded some of these can be quite staggering sonically especially with the improvements in Protools over the last few years (most feature films are mixed using this).

[Dr Bunsen Honeydew]

I've tried paper-in-oils in both the crossovers in my Tannoys, and as coupling caps in my preamp, and took them out nearly as quickly as they were put in, as they smoothed and slowed the the sound down too much, and so were replaced with high-quality polys (Clarity Cap MRs) and teflon-film types from SCR, which were to my ears, much more open, detailed and 'faster' sounding.

Perhaps results are different with valve amps?

However, I also know that paper-in-oils, in the right application can sound magical. It's just that my experience to date has shown that I generally prefer quality polypropylene caps. For me, they generally have less of a 'signature' - but that's ONLY based on the equipment I've used so far.

Again, experience so far tells me that I prefer quality polypropylene caps to most electrolytic types, for the same reasons as I explained before. For me, however, there is no automatic 'best' - it's all application and interface dependent. One has also to voice by ear accordingly in any scenario.

Totally agree! If there's one thing I can't stand is pointless red tape and bureaucracy!! The no-life muppets, who sit on their fat arses in offices all day, dreaming up how to make life the most difficult for everyone else, need a damn good slap! :steam:

I wish that more audio designers looked upon audio as a "highly delicate art form" (I totally agree), and didn't merely see it as a soulless 'black & white' entity for which current science has all the answers.... :rolleyes:

Marco.
Paper in oil needs a ridiculous run in time, until up they do sound slow. Best to buy second hand. I don't use them in sand amps, they are really only suitable for bottle amps. I use them in my crossovers though. I use polyprop' and some polystyrene that I add to the PCB after they have been flow soldered.

Metal oxide resistors have been around since the early 70's so are not new. The standard fodder now made in China is inferior to then, but there are Japanese manufacturers like Takman who are very good, but best by far are the sadly missed tantalum resistors made by Shinkho. The company having now closed, but if you can still find them they are seriously expensive. Hi Fi Collective seem to have cornered all the old stock. Audio Note have copied them for small scale production but they are not as good.

[Marco]

In terms of resolution I have no doubt that some of the amplifier designs referred to here are an audible marvel of resolution.

What I think would disappoint folk here greatly is the equipment and the quality thereof that some of these recordings that we buy are made on.

Having worked in studio and high-end post production environments for some years (I don't anymore as I'm far too old to be of any use and cannot survive on the minimum wage) I can vouch for the fact that much of the equipment is built to a very high standard but nowhere even approaching the quality of some of the machinery used by members of this forum and designed / built by Richard.

Modern recordings are to a very large extent pretty awful sounding and "mastered" (I use the term loosely) by 18 year olds "so that they sound like really like loud yeah..." You only have to rip one of the tracks of your favourite CD into your favourite wave editing package to see how compressed and hideous some recordings are - even the ones perporting to be "high end".


Totally agree, Stewart. However, when I mention a system achieving "high-fidelity", I mean merely a sound which is closest to replicating that of the source recording (good or bad) - and of course, as consumers, the latter is totally out with of our control :)

Marco.

[Dr Bunsen Honeydew]

My speakers mate i don't give two hoots what you think, i'd rather save the units than listern for things..besides i'm not using a fuse i'm using a QB resettable circuit breaker that are faster action & have a vastly smaller internal resistance of 0.3 Ohm as opposed to the standard fuse & fuse holder!
Well lets look at reality, my amps are unprotected and so are my speakers. Out of over 2000 amps being used worldwide I have had no failures that have taken out drive units in 2011. In 2010 we had the Wilson Benesch saga as referred to in this thread and one Ruark bass driver in the whole year. So how big a problem is it compared with Fff-up music that *any* form of protection circuit in the signal path gives you.

[Marco]

Hi Richard,


Paper in oil needs a ridiculous run in time, until up they do sound slow. Best to buy second hand.


Yup, indeed if that's the case, because the sort of PIOs I'd like to use (AN silver foils) are rather too expensive to be bought, left to run in, and then discarded after discovering that even after the run-in process, I still prefer my favourite polys, at a fraction of the price! ;)


I don't use them in sand amps, they are really only suitable for bottle amps. I use them in my crossovers though. I use polyprop' and some polystyrene that I add to the PCB after they have been flow soldered.


I had a feeling that PIOs were best when used in valve amps. One day I may try some really good ones, but for the moment I'll stick to my favourite Clarity Cap MRs and SCR teflons (for signal duties) and (Mundorf Tube Caps) for PSU applications.


Metal oxide resistors have been around since the early 70's so are not new. The standard fodder now made in China is inferior to then, but there are Japanese manufacturers like Takman who are very good, but best by far are the sadly missed tantalum resistors made by Shinkho. The company having now closed, but if you can still find them they are seriously expensive. Hi Fi Collective seem to have cornered all the old stock.


HFC is where I get most of my parts from. It was the Takman metal-film resistors I was referring to. Interesting about the Tantalums - I'll bear those in mind for my next project :)

Marco.

[swampy]

Interesting thread. I have an home built F5 and originally fitted fuses to the speaker output but these really affected the sound. I then tried a relay DC protection circuit but again, not great. In the end I removed it and wired directly. Much better sound-wise.

The F5 design does have built in current limit under short conditions but no DC protection. This is always the issue with most sand amps apart from the single ended ones like the F3 that use output caps on the + speaker line. Some directly coupled amps use more elaborate protection like crowbar.

I've had a KT88 p-p amp go bang, tubes flashed over and scared the crap out of me. Pops and cracks usually mean a cap or more likely a bad tube. When a power tube goes it can go big style. The only saving grace is the output tx usually protects the speakers from damage.
If the amp starts making cracking noises I'd be very cautious and don't leave it un-attended.

[Reid Malenfant]

Well lets look at reality, my amps are unprotected and so are my speakers. Out of over 2000 amps being used worldwide I have had no failures that have taken out drive units in 2011. In 2010 we had the Wilson Benesch saga as referred to in this thread and one Ruark bass driver in the whole year. So how big a problem is it compared with Fff-up music that *any* form of protection circuit in the signal path gives you.
You don't need to put anything in the signal path to protect equipment :doh:

Why can't you simply crowbar the mains & blow the fuse that really must be there for safetys sake. A simple circuit to detect DC offset (rather than melting voice coils) & a crowbar...

Not difficult is it, i suppose you have heard of a component called a triac?

[Dr Bunsen Honeydew]

They still mess up the music by increasing the impedance of the power supply.

You love this emoticon :doh: don't you, perhaps you over use it.

[anthonyTD]

You don't need to put anything in the signal path to protect equipment :doh:

Why can't you simply crowbar the mains & blow the fuse that really must be there for safetys sake. A simple circuit to detect DC offset (rather than melting voice coils) & a crowbar...

Not difficult is it, i suppose you have heard of a component called a triac?
Totaly agree!
Anthony,TD...

[Reid Malenfant]

So let me get this straight Richard, are you saying you don't incorporate a mains fuse into your amplifiers? Are you relying on the one that just happens to be fitted in the mains plug?

Have you considered that anyone could change that to a 13A version :mental:

[Dr Bunsen Honeydew]

Do you know anything at all about class 2 regs, do I have to give you a link again.

[Reid Malenfant]

Do you know anything at all about class 2 regs, do I have to give you a link again.
No, i'm not familiar with them as i'm not a manufacturer selling to the public or anyone else for that matter.

It wasn't a difficult question to answer, so i'd appreciate it if you could fill me in. A simple yes or no would do after all. Do you fit an internal mains fuse to your amplifiers?

Thanks in advance :)

[Dr Bunsen Honeydew]

No, i'm not familiar with them as i'm not a manufacturer selling to the public or anyone else for that matter.

It wasn't a difficult question to answer, so i'd appreciate it if you could fill me in. A simple yes or no would do after all. Do you fit an internal mains fuse to your amplifiers?

Thanks in advance :)
No, nor am I required to, you obviously have no knowledge about appliance regulations and yet you can attempt to diss me and my products, nice guy aren't you?

You obviously don't read threads before you spout, try this, it is simplistic so will suit you down to the ground.

http://en.wikipedia.org/wiki/Appliance_classes this link was posted only a couple of days ago.

If you wish to understand further you can go and take a course on it or get a full copy of the regs. It is not my job to teach you electronics.

Sorry Marco, but this is deserved.

[Marco]

Lol - just keep it less 'emotive' and strictly factual, Richard, and you'll be fine!

Mark, play nice with the ol' fella ;)

Marco.

[Reid Malenfant]

I wouldn't want you to teach me about electronics if you were the last person on the earth Richard :) I also don't need you to as i have worked at a couple of electronics firms doing test, repair & R & D on various bits of electronics ;)

Just because you might stick to the regulations doesn't stop you being one of the most un-safety concious designers i have ever come accross, with what appears to be bugger all regard for your customers equipment!

I'm sure there will be plenty more bass drivers catching fire in the not too distant future, after all it's just a question of time before the heating & cooling of silicon on the copper substrate causes another power transistor to go collector emitter short circuit :mental:

So it sounds like there is not a single fuse on the interior of your amplifiers. That's nice to know & i'm sure anyone who happens to run one or more will be eternally greatful that there loudspeakers are being treated with kidd gloves :)


Mark, play nice with the ol' fella
I'm trying my hardest :)

[spendorman]

I believe that Reid Malenfant has a similar background in electronics to myself and has a very good understanding of the subject.

[Dr Bunsen Honeydew]

There is that condescending streak again!

[Dr Bunsen Honeydew]

I believe that Reid Malenfant has a similar background in electronics to myself and has a very good understanding of the subject.

I have worked in the design of consumer electrics prior to working in electronics, albeit quite a few years ago, when British Standards ruled.

A basic rule is that the appliance should be fail safe. This obviously was not the case with the amplifier and speakers that caught fire.

In that situation, something else needed to be done to make the system safe.
BOLLOCKS!

YOU obviously don't understand! it has been explained over and over until I am blue in the face, the only company that faced prosecution over this was the speaker manufacturer. The ONLY company who broke regulations was the speaker manufacturer.

[Marco]

There is that condescending streak again!


Not intended to be condescending, Richard - merely a bit of friendly banter. We all rib each other a bit on AoS. It is not meant in a negative way. You'll appreciate this more when you've been here longer. I haven't even called you a 'daftee' yet! ;)

Marco.

[Reid Malenfant]

YOU obviously don't understand! it has been explained over and over until I am blue in the face, the only company that faced prosecution over this was the speaker manufacturer. The ONLY company who broke regulations was the speaker manufacturer.
I'm sure he understands perfectly well that a pair of speakers that operated with no problems being fed an AC signal from your amp/s obviously didn't have a shorted turn whilst they were being listened to.

Have you ever shorted a turn on a transformer & applied power to it? It's not pretty! So, as I understand things from an electrical point of view why didn't this loudspeaker with the so called shorted turn blow the amp while music was playing?

After all that's when it'll be supplying power :eyebrows:

Sorry old chap but it just doesn't wash...

I don't accept your version of events & anyone who is competent certainly wouldn't either i have a feeling :cool:

[Audioman]

Just have to chip in since knowone stated the obvious. Uk mains has a fused plug to protect the cable. In addition there are trips on the consumer unit (previously wire fuses). These are sensitive enough to trip out if anything goes wrong. Hence modern amps do not have fuses in the back as some classic kit did. In addition there is usualy an RCD which may cover the entire mains supply or just garage/kitchen. Overall the system should be adequately protected in instances of shorts. May not prevent component damage but complete burn out or possibility of electrocution.

[swampy]

Are you relying on the one that just happens to be fitted in the mains plug?

Have you considered that anyone could change that to a 13A version :mental:

Or a copper blank !! :stalks:

[Dr Bunsen Honeydew]

Just have to chip in since knowone stated the obvious. Uk mains has a fused plug to protect the cable. In addition there are trips on the consumer unit (previously wire fuses). These are sensitive enough to trip out if anything goes wrong. Hence modern amps do not have fuses in the back as some classic kit did. In addition there is usualy an RCD which may cover the entire mains supply or just garage/kitchen. Overall the system should be adequately protected in instances of shorts. May not prevent component damage but complete burn out or possibility of electrocution.
At last some bloody sense.

I have said it at least three times - what is a fuse? what does the word fuse mean? does it mean a tube of glass with a wire in it? NO. I have a fuse in the power supply in terms of something fuses when the current flow gets too high, but it is a component, not a bloody glass fuse that shits all over the current rating and impedance of the power supply. Apart from that people can mind their own bloody business, it is not my job to teach ignorant people electronics. That is fact, that is me! take it or leave it.

[spendorman]

Or a copper blank !! :stalks:

He he, I thought about that, been done, not be me though.

[Reid Malenfant]

Just have to chip in since knowone stated the obvious. Uk mains has a fused plug to protect the cable. In addition there are trips on the consumer unit (previously wire fuses). These are sensitive enough to trip out if anything goes wrong. Hence modern amps do not have fuses in the back as some classic kit did. In addition there is usualy an RCD which may cover the entire mains supply or just garage/kitchen. Overall the system should be adequately protected in instances of shorts. May not prevent component damage but complete burn out or possibility of electrocution.
Are you sure about this?

Have you noticed that the smallest value fuse you can fit in a mains plug is 3 Amps?

That is over 700 Watts at UK voltage of approximately 240V.

So you have a 60W amplifier with maybe a 100 - 150VA transformer, do you honestly think a 3A fuse will protect it?

Get real, stuff the regulations! It needs to be fused internally with at the most a 1A fuse!

[anthonyTD]

Just have to chip in since knowone stated the obvious. Uk mains has a fused plug to protect the cable. In addition there are trips on the consumer unit (previously wire fuses). These are sensitive enough to trip out if anything goes wrong. Hence modern amps do not have fuses in the back as some classic kit did. In addition there is usualy an RCD which may cover the entire mains supply or just garage/kitchen. Overall the system should be adequately protected in instances of shorts. May not prevent component damage but complete burn out or possibility of electrocution.
hi paul,
the type of fault that occured in this instance i fear would not have activated an RCD, all that would have happend is the unit would have drawn more current due to one or more of the output devices or the voltage rail becoming defective rendering the normaly self balancing output to become more positive or negative depending on which device or rail became faulty!
this would then turn an AC amplifier with normaly very low DC offset [within microvolts to millivolts]into a DC positive or negative current dump!
Anthony,TD...

[Dr Bunsen Honeydew]

I wouldn't want you to teach me about electronics if you were the last person on the earth Richard :) I also don't need you to as i have worked at a couple of electronics firms doing test, repair & R & D on various bits of electronics ;)

Just because you might stick to the regulations doesn't stop you being one of the most un-safety concious designers i have ever come accross, with what appears to be bugger all regard for your customers equipment!

I'm sure there will be plenty more bass drivers catching fire in the not too distant future, after all it's just a question of time before the heating & cooling of silicon on the copper substrate causes another power transistor to go collector emitter short circuit :mental:

So it sounds like there is not a single fuse on the interior of your amplifiers. That's nice to know & i'm sure anyone who happens to run one or more will be eternally greatful that there loudspeakers are being treated with kidd gloves :)


I'm trying my hardest :)

This is libel, please provide me with your real name and address for my solicitors. If not supplied then by law the owners and mods of this forum must supply it. If they don't then they become equally liable for the libel.

I will leave it up to you.

[spendorman]

hi paul,
the type of fault that occured in this instance i fear would not have activated an RCD, all that would have happend is the unit would have drawn more current due to one or more of the output devices or the voltage rail becoming defective rendering the normaly self balancing output to become more positive or negative depending on which device or rail became faulty!
this would then turn an AC amplifier with normaly very low DC offset [within microvolts to millivolts]into a DC positive or negative current dump!
Anthony,TD...


Absolutely, the RCD detects only the imbalance between live and neutral.

I accidentally cut through the hedge clipper mains cable, big flash, fuse in plug gone, but RCD not tripped. Hedge trimmer was double insulated. It's a good machine (from Lidl years ago), but cable was black, not the best colour for garden use. Changed it to an orange cable and have been more careful!

If nothing else, this thread has got many people thinking about safety of hi fi systems, not a bad thing.

[Reid Malenfant]

This is libel, please provide me with your real name and address for my solicitors. If not supplied then by law the owners and mods of this forum must supply it. If they don't then they become equally liable for the libel.

I will leave it up to you.
No it isn't :lol: It's the truth man! You might stick to the regs, but you just don't give a monkeys about other peoples equipment. NO PROTECTION, what are you thinking :rolleyes:

You really are the most nasty piece of work aren't you :eyebrows: Don't get your way & it's "i'll call in the lawyers". We can now all see how you'll stoop so low to keep up appearances :mental:

Oh, please don't forget that this is all "in my opinion" :ner:

[swampy]

The only components I have in my system that are solid-state are my CDP, DAC, and the PSU for my T/T, and those are left switched on 24/7.
Marco.

Maybe leaving solid state pre/ phono / dac / CDP is ok but I'd never leave any kind of tube amp on 24/7, nor a solid state power or integrated.

This thread has got me thinking I should have another go at refitting my DC protection module on my diy F5....:scratch:

The F3 uses a largish cap on the + output rail and it sounds not that dis-similar to the F5 which is direct coupled. I did wonder about trying a large non polar cap on the F5 + output but is this a really silly idea ???

Some vintage sand amps which had a single ended PSU needed such an output cap.

[Marco]

No it isn't :lol: It's the truth man! You might stick to the regs, but you just don't give a monkeys about other peoples equipment. NO PROTECTION, what are you thinking :rolleyes:

You really are the most nasty piece of work aren't you :eyebrows: Don't get your way & it's "i'll call in the lawyers". We can now all see how you'll stoop so low to keep up appearances :mental:

Oh, please don't forget that this is all "in my opinion" :ner:

Ok, guys, both of you, that's quite enough now for today. This is going nowhere and it's now turning personal. Therefore, any further continuation of this argument will be deleted without further warning.

Marco.

[Marco]

Hi David,


Maybe leaving solid state pre/ phono / dac / CDP is ok but I'd never leave any kind of tube amp on 24/7, nor a solid state power or integrated.


Indeed, dude, hence why I said so earlier. No WAY would I leave my valve amps on for an extended period of time, unattended!

Btw, on a totally unrelated subject, are you still up for building modified crossovers for Tannoys? If so, I've got a friend you could help :)

Marco.

[Audioman]

hi paul,
the type of fault that occured in this instance i fear would not have activated an RCD, all that would have happend is the unit would have drawn more current due to one or more of the output devices or the voltage rail becoming defective rendering the normaly self balancing output to become more positive or negative depending on which device or rail became faulty!
this would then turn an AC amplifier with normaly very low DC offset [within microvolts to millivolts]into a DC positive or negative current dump!
Anthony,TD...

Anthony

This appears to be an extremely nasty and I hope rare fault and I bow to your expertice. I was refering more to a particular forum member (Reid Malenfant) who is insisting on internal fuses on everything. I would think he would be adequately protected by the consumer unit trips if the 13/5/3 amp did not blow. This would probably protect a total meltdown and fire as well as possibility of electrocution. Of course it cannot prevent internal damage anymore than a 1 amp internal fuse in all circumstances. Lower value fuses certainly slug the sound. I have found replacing a 5 amp with 13 amp in the plug for a CD player improves sound. You will find most audiophile mains cables are supplied with 13 amp fuse only and are intended for use with all components.

Paul

[Reid Malenfant]

This appears to be an extremely nasty and I hope rare fault and I bow to your expertice. I was refering more to a particular forum member (Reid Malenfant) who is insisting on internal fuses on everything. I would think he would be adequately protected by the consumer unit trips if the 13/5/3 amp did not blow. This would probably protect a total meltdown and fire as well as possibility of electrocution. Of course it cannot prevent internal damage anymore than a 1 amp internal fuse in all circumstances. Lower value fuses certainly slug the sound. I have found replacing a 5 amp with 13 amp in the plug for a CD player improves sound. You will find most audiophile mains cables are supplied with 13 amp fuse only and are intended for use with all components.

Paul
No Paul, it's not a rare fault at all. It happens to all transistors sooner or later, it's just a question of time & how much heat they have to dissipate as well as the difference between the cold & hot temperature.

The bigger the difference the sooner the transistor will fail. You see silicon expands at a different rate to the copper substrate, so as it ages it begins to break away from the substrate & can't dissipate as much heat. It's a viscious circle that ends up with the transistor failing! As it gets hot it begins to break away due to the different thermal expansion of the metals, because of this it gets hotter because it can't get rid of the heat (due to it breaking away from the copper substrate) so it gets hotter & breaks away more, so it's harder to dissipate heat, so it gets hotter, etc...

[swampy]

Anthony
You will find most audiophile mains cables are supplied with 13 amp fuse only and are intended for use with all components.

Paul

From my understanding (which may be flawed ?) .... Such fuses (i.e 13A) in these audio mains leads just protect the lead itself, not the equipment it is connected to, or you for that matter (an RCD does that later part). The plug fuse would protect a dead short on the mains lead which may otherwise lead to a fire, the mains IEC of the amp and maybe if the primary of the mains tx goes dead short. However a fault on the secondary side of the mains tx or amp inself; it will do bugger all to prevent a disaster.

[spendorman]

I believe that originally the Quad 405 had no real protection against outputting DC.

As an afterthought, a crowbar protection board was mounted on the speaker output terminals.

I know that this worked on several occasions, having repaired several 405's.

[anthonyTD]

Anthony

This appears to be an extremely nasty and I hope rare fault and I bow to your expertice. I was refering more to a particular forum member (Reid Malenfant) who is insisting on internal fuses on everything. I would think he would be adequately protected by the consumer unit trips if the 13/5/3 amp did not blow. This would probably protect a total meltdown and fire as well as possibility of electrocution. Of course it cannot prevent internal damage anymore than a 1 amp internal fuse in all circumstances. Lower value fuses certainly slug the sound. I have found replacing a 5 amp with 13 amp in the plug for a CD player improves sound. You will find most audiophile mains cables are supplied with 13 amp fuse only and are intended for use with all components.

Paul

hi paul,
on the subject of fuses, yes, i agree in some instances a marked improvement can be heard when changing the right rated fuse for a larger higher current capable type, its just plain old resistance, however, the same improvements can be had by fitting a larger than adequate mains transformer to start with.
Irispective of whether this type of failier happens rarely or often, it does happen, and when a designer or manufacturer produces a piece of equipment that has the potential to cause this type of damage when it fails, IMHO it is of the utmost importance to do all that is necessary to protect the end user from all eventualities that could arise from such potential catastrophic failiers.
Anthony,TD...

[anthonyTD]

I am drawn back in again as this is complete fucking nonsense. I have amplifiers that have been used everyday for 30 years with no transistor failure, in fact all of them as they only fail due to outside circumstances. AND so does every other long term transistor amp manufacturer. Do you really think that Naim would lose the trick of an expensive output stage replacement (like they do with PSU caps) if this was true and they have nearer 40 years of amps out there.

This is the last one, I have had it with a forum that allows libel to be perpetrated on its pages, the next contact will be legal.
hi Richard,
i dont see libel only a diffrence of opinion of how important the safety aspect must be considered when supplying a product to the genral public.:scratch:
yes it may have gotten a bit out of hand at times but if you truly believe that IYHO you think the risk of not fitting internal protection to your power amps is worth the added sonic improvements then just say so and leave it at that, the good folk here can then make up their own mind whether this type of equipment is for them or not.
Anthony,TD...

[swampy]

As long as the customer is aware of an amplifiers lack of output protection then it should not be a problem, leave it up to the buyer to decide. Maybe they could have a buyer option of output protect relay fitted or not as long as they know the compromise if fitted ?

[Marco]

hi Richard,
i dont see libel only a diffrence of opinion of how important the safety aspect must be considered when supplying a product to the genral public.:scratch:
yes it may have gotten a bit out of hand at times but if you truly believe that IYHO you think the risk of not fitting internal protection to your power amps is worth the added sonic improvements then just say so and leave it at that, the good folk here can then make up their own mind whether this type of equipment is for them or not.
Anthony,TD...

+1, particularly the bit in bold.

Richard, you're not banned, and so are welcome to contribute when you wish, or not. The decision is yours.

But leave off of the libel nonsense. There is no libel. If I genuinely thought that there was, it would be removed instantly. There is only OPINION. Cawley tried that pish, if you remember, over me reporting his (provable) dishonest misdemeanours with Mike New, and look where it got him ;)

So don't be daft. Lick your wounds and come back when you're ready.

Marco.

[Marco]

Hi David,


As long as the customer is aware of an amplifiers lack of output protection then it should not be a problem, leave it up to the buyer to decide. Maybe they could have a buyer option of output protect relay fitted or not as long as they know the compromise if fitted ?

Did you miss what I asked you about the Tannoys earlier? :)

Marco.

[swampy]

Errr, yes.... what did you ask.

[Marco]

Lol - this:


Btw, on a totally unrelated subject, are you still up for building modified crossovers for Tannoys? If so, I've got a friend you could help :)


Marco.

[swampy]

Do you still have a copy of the final circuit. I remember Dave H tweaked the circuit you originally proposed which ended up being the one used when you fitted the premium parts. Otherwise would need good photos of the board to reverse engineer.

[Marco]

Yup, I've got all that dude, but it's not for me. It's for someone who's got Tannoy Ardens, which use 15" HPD drivers, not Monitor Golds (like mine), so the crossovers will be different.

What I'd need you to do is have a look at the current circuit for his crossovers, and the bits used, and recommend which components to modify and/or upgrade :)

Marco.

[Marco]

{Continual argumentative posts between Mark and Richard removed}

Ok, guys, that's enough for today. I'm locking this thread until the morning, as I'm about to go to bed, and don't want to wake up tomorrow with a whole pile of crap to delete!

Nighty, night :goodnight:

Marco.

[Marco]

Thread now re-opened, so play nicely, chaps - and I mean that! ;)

Richard appears to have resigned his desire to post on AoS, due to him considering that he's been libelled and unfairly treated. I won't comment further on this, and instead allow people to make up their own minds whether his accusations have any basis in reality. He however has not been banned and so still retains his right of reply.

What I would appreciate some feedback on, getting the thread back on course, is some recent comments about the use of equipment fuses on Richard's forum (see here:http://thehifisubjectivist.noadforum.com/viewtopic.php?f=4&t=438#p7497), such as this from Lindsay T (why this chap doesn't post here, if likes the discussions so much, I've no idea):


Very interesting and informative post in the AoS thread about the quality of passive electriconic components not being as good as it used to be.

Also, reading that thread it seems that some people's definition of safety in electronic items means having bolt-on dedicated safety-only components such as wire-in-glass fuses or circuit breakers. Whilst, another approach - that seems to be more elegant to me from an engineering point of view - is to have components that would be there anyway for optimum functioning of the device, such as resistors, that also double as safety features.


This is apparently what Richard was getting at. Would someone with the requisite technical knowledge, and extensive experience of designing audio equipment, care to comment on the efficacy of what is being suggested?

Cheers! :cool:

Marco.

[hifi_dave]

Fusing resistors are/were often used in valve amps to protect circuitry when things go wrong. Not sure if they still are ?

In my experience, these fusing resistors sometimes cause a whole heap of problems. I won't mention any amps in particular but I have seen very badly burnt out PCB's and associated components caused whilst the fusing resistors were burning out.

The problem appeared to be that the fusing resistors would heat up and glow for some time before they went open circuit and all the time were causing damage to surrounding parts with some spectacular fireworks..:eek:

[roob]

I am afraid it's only a matter of time before Richard is banned from here, the same happens on every other HiFi forum he joins.

[Rare Bird]

A very famous Valve amplifier design uses a protection resistor to protect it's mains transformer, when it gets too hot it physically desolders itself, hence cuts out the amp, saves the transformer from damage...

[spendorman]

A very famous Valve amplifier design uses a protection resistor to protect it's mains transformer, when it gets too hot it physically desolders itself, hence cuts out the amp, saves the transformer from damage...

I was thinking about you mentioning this to me. It's am amp who's name sounds like a vegetable!

or unwanted water!!

[AlexM]

No wish to stir the pot, but here is my personal POV on the issues being discussed.

Personally I would prefer my equipment to be designed in such a way as to prevent excessive damage to itself or associated equipment in the event of a component failure.

I have some sympathy for Richard's POV in that a fuse doesn't necessarily mean a glass tube with a fusable link, but I would want the protection mechanisms to be RELIABLE, and not rely on the destruction of internal components that are expensive to replace (i.e. not rely on the output stage destroying itself!.

If one is prepared to accept additional cost and complexity, I don't know why this has to necessarily be prejudicial to sound quality. How about PSU rail monitoring or output stage temperature and current monitoring to allow shutdown if the safe operating area of the devices is exceeded?.

From a design/manufacturer like Richard's POV I guess that at a given price point, the greater the proportion of the bill of materials spent on protection measures, the less money is available to spend on improving sound quality which is also important to consumers and gives a greater competitive advantage.

In any case, how many prospective purchasers will have access to information about how 'safe' or well protected any piece of equipment is, relative to others and how would this influence their purchasing decision (even if they could do a comparative evaluation). Most people will go through ownership of a piece of equipment without experiencing this, but if it had happened to me it would certainly be a major consideration in future purchases!.

I say all of this as an owner of valve amp which will no doubt ignite in a shower of sparks and smoke at some stage!. I thought that most transformers have a thermal fuse that blows before the windings reach a temperature where the insulation will break down. My Phillips 'Scope has a cartridge-type thermal fuse in the transformer. I blew it (don't it ask me how :rolleyes:), and replaced it with a latching resettable thermal diode, but maybe too many KvA to do this with audio xformers).

Regards,
Alex

[anthonyTD]

I was thinking about you mentioning this to me. It's am amp who's name sounds like a vegetable!

or unwanted water!!
Quad also did a similar thing with its original valve mono-blocks, although when it unsoldered itself it only protected the output valves from drawing excessive current it being the Cathode resistor!
Anthony,TD...

[spendorman]

Quad also did a similar thing with its original valve mono-blocks, although when it unsoldered itself it only protected the output valves from drawing excessive current it being the Cathode resistor!
Anthony,TD...

I was referring to the Leak of course.

I did not know that the Quad I had fuseable link.

[anthonyTD]

I was referring to the Leak of course.

I did not know that the Quad I had fuseable link.
hi Alex,
i knew exactly who you were refering to having had many Stereo 20's on the bench over the years.:)
I was merely commenting on the fact that...Quad also used a similar protection method.
Anthony,TD...

[spendorman]

hi Alex,
i knew exactly who you were refering to having had many Stereo 20's on the bench over the years.:)
I was merely commenting on the fact that...Quad also used a similar protection method.
Anthony,TD...

It was just for any members that did not know.

[anthonyTD]

It was just for any members that did not know.
AHHH,
sorry Alex.:)
A...

[DSJR]

I'm sure there are wonderful sounding amps out there with fuses in their DC lines. The resistance of these fuses, if measurable, would have been taken into account in the design process surely????? I mean, Quad apparently took the capacitance of their internal cabling into account with the II valve amps for example.

[swampy]

A very famous Valve amplifier design uses a protection resistor to protect it's mains transformer, when it gets too hot it physically desolders itself, hence cuts out the amp, saves the transformer from damage...

The small denon midi systems use a similar thing... a thermal fuse inside the mains tx. Quite common to have a thermal fuse in such mainstream mid-fi so that if something cooks due to a fault it fuses itself and cuts the supply (permanently)... needs to be replaced.

[spendorman]

The small denon midi systems use a similar thing... a thermal fuse inside the mains tx. Quite common to have a thermal fuse in such mainstream mid-fi so that if something cooks due to a fault it fuses itself and cuts the supply (permanently)... needs to be replaced.

Microtemp or something similar possibly. I designed them into domestic electrical equipment years ago. Sandwich toasters, deep fat fryers, steam irons, etc. etc.

[The Black Adder]

I've only recently seen this threads posts and have been quite taken aback to be honest with the response.

In all fairness Richards amps are mighty fine sounding and I always make that known when someone is selling an A80 set or simular. They sound really very good indeed. But because of what happend to me I can only say to people that turning off your kit regardless of make is probably the best thing to do.

As in my previous post manufactures like Chord seem to do a pretty good job at making amplifiers sound great with very robust safty protection circuits.

To this I would suggest to Richard (from my own experience) that he should look in to implimenting such a circuit.

Surely the difference with a protection circuit can't damage the sound to the ends that people would turn away?

[Tim]

I've only recently seen this threads posts and have been quite taken aback to be honest with the response.
You should have seen the posts that Marco deleted! I was shocked someone in the trade felt the need to vent so aggressively and abusively :scratch:

Shame really as I feel Richard is only doing harm to what seems to be a good reputation when it comes to his products, I would certainly think twice about buying anything from NVA now :(

[southall-1998]

My father owns an NVA Phono-2, and it's a lovely phono stage.

[barry-potter]

Shame really as I feel Richard is only doing harm to what seems to be a good reputation when it comes to his products, I would certainly think twice about buying anything from NVA now :(

that's probably why he is going on about libel............

[roob]

You should have seen the posts that Marco deleted! I was shocked someone in the trade felt the need to vent so aggressively and abusively
It happened on pfm and the Wam, nice gear shame about the owner.

[Slippershod]

not a dig at richard, or anyone else in fact, just an excuse to post:

http://www.youtube.com/watch?v=lf3BNRF9ICc

remember: it's the music that counts, gentlemen.

[WOStantonCS100]

I'm not a cheerleader for either side; but, after reading through this over again, there is one fact that just keeps glaring back at me.

The speaker caught fire and burned. The amp did not.

I don't have a dog in this race and I'm not vested either way. Nevertheless, if the brakes in my car fail, it doesn't seem to make sense to blame the engine for putting out too much horsepower. Maybe that makes sense; maybe it doesn't. :scratch:

[Marco]

Hi Biff,

That's an interesting way of looking at it!

For reference, in case no-one's been looking at the thread on Richard's forum, here is a detailed explanation of his policy regarding fault protection on his amplifiers:


Lets look at these claims of safety. Firstly when the amps were designed in terms of safety they were *exactly* the same in safety respects as the then current Naim and Exposure amps and other companies that have died since. No Zobel network and no output protection and all those products including ours were built to Class 1 appliance regulations.

Once again for those that don't know http://en.wikipedia.org/wiki/Appliance_classes So we all had case fuses to protect the user against an internal short on to a single insulated case. On the introduction of CE regulation everyone was moaning that we would not be able to make good amplifiers any more due to the safety regs.

I analysed the regs and realised by switching to Class 2 double insulated regs I could continue using my circuit the way I wanted to, it seems the others didn't discover this so they had a distinct disadvantage as they redesigned to meet CE. But in Naims case the brainwash and the marketing bullshit overcame it.

This meant that because of Class 2 regs I could no longer use detachable mains leads as the Class 2 says leads have to be attached internally. I also had to dispense with a case fuse as for one thing the case was now a total insulator and could not carry a current on any part of it being made of acrylic and the fuse holder itself was only single insulated so would have stopped the amp passing Class 2 regs. I was very happy about this as I wanted to get rid of both anyway, as they both mess up the music to a small degree.

So now people are noticing that early pre CE Naims and especially Exposures are musically superior to what they make now - so now you know why!!

It should also be noted the hypocrisy of AnthonyTD in the fact that no valve amplifier ever made would pass CE in any shape or form and are as inherently safe or unsafe as they have ever been. All valve amp companies do is self certificate and hope no one ever takes them up on it, and no one has.

This has made people realise that CE is not worth the paper it is written on as all valve amp manufacturers should have been seen off by the regs, and then all the other subsequent EU safety regs and now the disposal regs are not enforced as well, as countries do not want to make the money available to create the bureaucracy or employ the staff to enforce them. This is one of the hidden secrets about Hi-Fi at the moment.

So how do I protect my amplifiers against malfunction, well in one way I don't and in one way I do. Fuses I will not use, anything that increases the power supply impedance or throttles it in any way I will not use. I rely on resistors on the PCB on the power supply feed and the emitter resistors on the output stage to act as my fuse, as when there is a fault they burn out i.e. they *fuse*.

This makes some small fumes and damages the board, but for me it is cheaper to replace a board than try to repair it as other things will have been stressed by the failure and it is just not worth taking the chance of another failure due to that stress, so better to replace the whole lot, which is what I do. In the process we either do not charge or we charge about 25% for the work that other companies charge, as I am not interested in making profit from *service*.

Now regarding the safety regs and *those* loudspeakers that started this whole thing. Well obviously the amplifier fused the voice coil, and if that was it then that was it, a simple repair and driver replacement, but that fusing had a chain of events that followed it which should never have happened if the speaker was competently designed.

It has a heavy duty voice coil which means it needs a lot of current to fuse, but the voice coil obviously had a short circuit between at least some of its windings before this burn out as is shown by the photo of the former that the coil is wound on. This meant initially the heat of the fuse was concentrated in one place, this should have been no problem apart from the laquer used on the voice coil to hold it in place was inflammable (a complete no no on safety regs) so it initiated a flame.

This then set alight the wadding in the speaker which again was inflammable (once more a complete no no on safety regs), and then set on fire and melted the material the cone was made from (once again a complete no no on the safety regs). So what should have been a simple repair and driver replacement became this drama. So I ask anyone to say *WHO* bares responsibility for this.


Comments on the above, from the suitably qualified, would be welcome :)

Marco.

[The Black Adder]

The speaker caught fire and burned. The amp did not.:scratch:

I missed that post... Not entirely true or correct and not a very good statement unfortunately from Richard. Firstly I don't think there has ever been an amplifier made from paper and given more time who knows what would have happened to the amps as both monoblocks were sat there buzzing and smoldering away.

But let's look at this in another way... Both monoblocks were more or less at the same stage of meltdown... would this suggest an external powersurge?

[Alex_UK]

I have avoided getting involved in any of these discussions, mainly because I am not "suitably qualified" - probably like a lot of people who buy equipment from a manufacturer and just expect it to be safe. However, from that standpoint - as a mere customer - the last three paragraphs of RD's explanation worries me, in that surely a lot of people will be using vintage speakers, and I'm prepared to bet that safety regulations have evolved a lot since the 1950/60s? Do vintage Tannoys etc. have flame retardant lacquer on their drivers, and wadding that won't burn? Bitumen - a common material used in old speakers - will burn like wildfire - (pardon the pun.) And how many DIYers will be aware they need to use materials that won't burn?

To me, as a mere layman, a manufacturer relying on an (unknown) speaker to prevent a fire is bolting the stable door after the horse has bolted. In my personal opinion, blaming the speaker is not the answer - and I will now double-check the safety protection on any amplifier I buy in the future, and I will no longer be leaving my amplifiers on 24/7 - whether they are unprotected or not.

[jandl100]

A very sensible and well thought out post, Alex - from one "not suitably qualified" layman to another!

[The Black Adder]

I agree... That is now my of seeing things too Alex.

Also... if you don't have them already, buy some smoke alarms. Makes total sense regardless.

[Marco]

A very sensible and well thought out post, Alex - from one "not suitably qualified" layman to another!

Indeed. Don't get me wrong, guys, comments from anyone are welcome, as long as 'laymen' like Alex, your good self (and me!) don't discuss any technicalities on which we're not qualified to comment.

Just stick to general observations, as you've been doing :)

Marco.

[Clive]

I will no longer be leaving my amplifiers on 24/7 - whether they are unprotected or not.
Ever since I had a capacitor failure in an EL34 amp I built I have not left my amps on while I'm away from the room for more than a few mins. The EL34 capacitor episode occurred while I was mowing the lawn. One valve was glowing bright red and the output transformer was very, very hot. Heaven knows when a fire would have started. Yes the amps were diy (from a kit), but the capacitor was a good make (EVOX RIFA), it simply shorted internally. The amp had a fuse and the same protection most valve amps have. Do I have a smoke alarm? You bet and it's close to my amps!

[The Black Adder]

If only amplifiers were organic... they could look after themselves... lol

[Ali Tait]

I have avoided getting involved in any of these discussions, mainly because I am not "suitably qualified" - probably like a lot of people who buy equipment from a manufacturer and just expect it to be safe. However, from that standpoint - as a mere customer - the last three paragraphs of RD's explanation worries me, in that surely a lot of people will be using vintage speakers, and I'm prepared to bet that safety regulations have evolved a lot since the 1950/60s? Do vintage Tannoys etc. have flame retardant lacquer on their drivers, and wadding that won't burn? Bitumen - a common material used in old speakers - will burn like wildfire - (pardon the pun.) And how many DIYers will be aware they need to use materials that won't burn?

To me, as a mere layman, a manufacturer relying on an (unknown) speaker to prevent a fire is bolting the stable door after the horse has bolted. In my personal opinion, blaming the speaker is not the answer - and I will now double-check the safety protection on any amplifier I buy in the future, and I will no longer be leaving my amplifiers on 24/7 - whether they are unprotected or not.

Alex, these regs are for registered companies that sell electrical goods to the public. They do not cover anything you make and use yourself (diy) so you can do as you please in your own home.

[The Black Adder]

Last night I switched on my system to warm up ready for my usual nightly listening sesh, put the kettle on for a cuppa, opened the package containing the new Adele album that arrived yesterday morning to give that a whirl in the CD player.

Played track number 1 fine, around 10 seconds into track 2 the speakers let out the biggest bang you could ever imagine AND I INSTANTLY BLEMISHED MY UNDERWEAR :( I stood there in total shock expecting a huge cloud of acrid smoke from either the amp or speakers - my ears were still ringing a minute later, but no signs of smoke, no smell of burning and the CD was happily playing away at the same low volume level I had it at. Amp was as warm as normal, sniffed around the vents and no telltale smells emanating from it, placed my finger gently on all the bass/mid cones and they were doing as they should be doing. Ear pressed to each tweeter - fine.

I am donald ducked if I know what on earth caused this massive bang. I didn't notice the lights dim or brighten (perhaps they did), the missus said the telly and lights in the lounge were fine. If it was a mains surge, the the Belkin PF30 should have caught that one would assume :scratch:

Any road up, despite much trepidation and nail biting, I listened to the rest of Adele at low volume, then played the whole of Yello's Baby and cranked the volume up halfway - was fine.

Frank.. Have you had this problem since? I've got a slight rustling sound on my amp, gawd knows what it is.

Be getting fixed up by Nick soon enough though..

btw.. apologies for the hi-jack there... I didn't mean to cause a frakka!

[Alex_UK]

Alex, these regs are for registered companies that sell electrical goods to the public. They do not cover anything you make and use yourself (diy) so you can do as you please in your own home.

Hi Ali - yes, I appreciate that the regs don't apply to DIY - even more important then that people are aware of what can happen, and if using an unprotected circuit don't leave the amp on and unattended!

[Clive]

Hi Ali - yes, I appreciate that the regs don't apply to DIY - even more important then that people are aware of what can happen, and if using an unprotected circuit don't leave the amp on and unattended!
I think even "protected" cannot allow for all eventualities. Electronics will fail at some point, components do not have an infinite lifetime.

[Ali Tait]

Hi Ali - yes, I appreciate that the regs don't apply to DIY - even more important then that people are aware of what can happen, and if using an unprotected circuit don't leave the amp on and unattended!

Most of the folk who build their own stuff pretty much know what they are doing and are very aware of the dangers, particularly with valve stuff. The breadboarded amps made by the likes of Nick often contain thousands rather than hundreds of volts, so you have no choice but to be very careful, as you won't get a second chance!

[Jonboy]

I had a old Valve amp go up in smoke the other week as we were looking at it, one channel went down so my very quilified mate had a fiddle with it while still swithiched on as is normal practice if you know what you are doing, sparks and smoke started being emmitted so the fused plug was pulled out quick, it was a dodgy valve holder which shorted out due to corrosion we saved the amp but i lost a ECL86, cheap loss i suppose you could say, but just think what would of happened if i had just popped out :eek:, lesson learnt never leave anything on and unattended especially a valve amp as the fuse in the plug won't stop it going up in flames and also giving one a potential melted house or worse to go with it, don't bere thinking about really does it

[Ammonite Audio]

I had a KT88 fail in my old WAD KaT88 amplifer, fortunately as I was almost standing over it. There was an impressive display of purple fireworks inside the peccant tube, followed rapidly by foul smoke pouring out from components that were suddenly faced with lots of wiggly amps that they were not designed for. I had to pull the plug to stop things, so the internal fuse (correctly specced) did not stop the situation from getting much worse. So, I have some sympathy for Richard's statement about the safety of valve amps, but that aside I would prefer my gear to have 'fail to safety' design features. Surely it's possible to implement safety circuitry without an unacceptable penalty in sound quality terms. All that said, I would still be happy to have any of Richard's amps in my home, since the price/performance ratio is rather good and I do think you'd have to go a long way to match his customer service and support.

[Clive]

I suspect that rather than trying implement all sorts of fancy circuitry it might be better to sense the current drawn, if this goes over a preset limit then the power automatically shuts down. Frying components usually involves copious amounts of current.

[spendorman]

Alex, these regs are for registered companies that sell electrical goods to the public. They do not cover anything you make and use yourself (diy) so you can do as you please in your own home.

Yes, but bear in mind that household insurance might be invalidated by home built equipment that the insurance company may not consider safe.

[Jonboy]

Yes, but bear in mind that household insurance might be invalidated by home built equipment that the insurance company may not consider safe.

The same might be said of many a vintage piece as well, not only with Hifi as well, is it retrospective though, ie if it was safe then is it now

[Marco]

I think that this, from Richard, deserves to be seen:


OK I am getting piss sick of Black Adder, he got nothing but service, advice and help over many phone calls. FOC replacement amps (that I think he sold for a profit as the insurance paid him as well), but zero help and even rudeness from the speaker company. And yet for some reason he seems to forget everything done and discussed.

The amp that went DC was the bottom amp of two stacked on top of each other, it got very hot when or before it went DC for some unknown reason. It is not advisable to stack power amps where they can't breath. Also heat rises and that transferred to the top amp and over heated it, but apart from a mild repair it was fine and did nothing to the other speaker. NOTHING got outside of the amplifier case, it can't, the temperature required to ignite acrylic is far higher than the amp is capable of reaching, all that happens is the acrylic slightly distorts in places of high heat as it would melt long before igniting. It is a sealed case so if there was a fire it would be deprived of oxygen so fire cannot take hold and apart from that there is NOTHING inside the amplifier that is flammable, there are things that will fuse when the circuit pops and they will make a little smoke and smell, and that is it!! The amplifiers were quite safe, the thing that wasn't safe was the loudspeaker.

Regarding this other nonsense about old loudspeakers. Old loudspeakers mostly used lambs wool as wadding, try setting fire to it, it won't burn unless subject to a blow torch and even then reluctantly. Paper cones are very flame retardant as even then they were treated and even then the worst they will do is smoulder, they wont catch fire melt and put out noxious fumes. Plus in the old loudspeakers like Tannoy etc there was so much space between the voice coils and the cone there is no chance of anything passing between them. Modern speakers like this one are a different problem, due the desire for being compact and WAF then it can be a problem, being made worse by the high power voice coil in this case in what is a small speaker.

I have never experience a similar case to this and it is the only time it has happened involving NVA amps in over 30 years.


Marco.

[spendorman]

I've been toying with this problem for a while and have thought of several ideas, none of which are ideal.

I suppose desirable is an amp that is not likely to pass heavy DC in a fault situation and a speaker that does not easily cause a fire.

In my experience, amps with capacitor coupled outputs are less likely to pass heavy DC, although this can happen if an output capacitor fails short circuit, but I reckon this is far less likely.

I have often worried about direct coupled amps and valuable speakers. But fire hazard is another thought.

[AlexM]

Marco,

CE regulations cover both product safety and RF emissions and immunity. I presume that Richard's comments about moving to a double insulated Class-2 design deal with safety aspects.

I had thought that RF suppression was the bugbear of designers when these regulations were introduced, so I'm not sure what the pertinence of whether a design is Class-1 or Class-2 to sound quality is. The elimination of a case fuse is a red herring as the amp could still be fused internally.

W.r.t. to this incident the main question seems to be did a short in the voicecoil precipitate a failure in the amplifiers, or did the DC latching of the output stage cause a short in the voicecoil?.

This is the key question in initiating the chain of events - the subsequent events (coil insulation overheating, internal fire etc) would not have occurred without this initiation, although I'd agree with Richard that the consequences were potentially worsened, and the chain could have potentially been broken had the voice coil not had flammable lacquer etc etc.

If it is true that an output stage failure on the amp could have precipitated the failure and overheating of the voicecoil by dumping DC rail voltages on the speaker cables, then I'm not sure why it has been analyzed that the initiation was a voice coil short?. Even if it was the chain of events could have been broken had one of a number of protection devices been in place. I think that the root cause of this is not correctly attributed.

Regards,
Alex

P.S. Just read your subsequent post from Richard... I was going to include something in my post about avoiding ad-hominem attachs on Richard, but he doesn't seem to feel similarly constrained!.

[Audioman]

Alex, these regs are for registered companies that sell electrical goods to the public. They do not cover anything you make and use yourself (diy) so you can do as you please in your own home.

Yes you can do what you like but some knowledge as to what is safe practice and what is not is a requirment for self builders. Otherwise stick to bought kit unless following a competent design to the letter.

Speaking as a lay person Richard's comments make good sense. I think his demenour on internet forums should not cloud our judgement as to his knowledge and compitence. Personaly I am not keen on captive cable designs with glued together plastic cases. However you have to admire someone who will not compromise on his design principles and NVA has a good reputation for sound per pound.

I would agree that leaving equipment on 24/7 is not worth the risk (certainly power amps). This was first put forward by RA some years ago. Following this advice and leaving my CD player permanently on suddenly resulted in it going in for regular and expensive repairs !

[spendorman]

The same might be said of many a vintage piece as well, not only with Hifi as well, is it retrospective though, ie if it was safe then is it now


The insurance company may not take it that way. The production vintage equipment would likely be OK for regulations at it's time of manufacture.

Modern, potentially unsafe home brew equipment is probably less likely to escape their scrutiny.

Don't get me wrong, I like home-made stuff, but attention to safety, needs to be considered carefully.

He says, with a Williamson amplifier and no base plate on it! Still, if I got it into service would have to make one and a protective cage to go over the top.

[The Black Adder]

Thanks for that Marco but why did he not post this?

I have a reply to this 'private' mail to Marco but I will restrain myself from a big rant as I want to stop this here and NOW.

In my defence I will just awnser some of his points that were directly aimed at me and some points experienced first hand of the event .

A. It's not my fault for stacking the amps. I don't fecking think so.
B. I did not sell for a profit.
C: The lids of the amplifiers were buckled and letting toxic fumes out.. so therefore they were not sealed once the heat got to the acrylic cases.
D: If you say they cannot breath then either put deeper feet on them, vent them or simply place a sticker on the top of the amps saying "DO NOT STACK".

[Marco]

'Cos he doesn't feel he can post at the moment without being unfairly attacked. Therefore, I'm copying and pasting all the relevant bits.

Marco.

P.S I'll get to your Tannoy query as soon as I can.

[Ali Tait]

Yes you can do what you like but some knowledge as to what is safe practice and what is not is a requirment for self builders. Otherwise stick to bought kit unless following a competent design to the letter.

Speaking as a lay person Richard's comments make good sense. I think his demenour on internet forums should not cloud our judgement as to his knowledge and compitence. Personaly I am not keen on captive cable designs with glued together plastic cases. However you have too admire someone who will not compromise on his design principles and NVA has a good reputation for sound per pound.

I would agree that leaving equipment on 24/7 is not worth the risk (certainly power amps). This was first put forward by RA some years ago. Following this advice and leaving my CD player permanently on suddenly resulted in it going in for regular and expensive repairs !
Well I would hope that any diy'er would have the sense not to build or do stupid things that may put themselves and others at risk. If they do they should not be diy'ing!

[Ali Tait]

I suspect that rather than trying implement all sorts of fancy circuitry it might be better to sense the current drawn, if this goes over a preset limit then the power automatically shuts down. Frying components usually involves copious amounts of current.

Being direct-coupled, with the potential for danger that brings, the amps Nick is building for my statics have exactly such a circuit built in, which will shut them down if anything untoward is sensed.

[Beobloke]

Comments....from the suitably qualified, would be welcome :)

Marco.

I am actually suitably qualified but I'm staying WELL clear of this one!

Carry on though, everyone - it's most entertaining! ;)

[The Black Adder]

Nah.. I've risen to his last statement and set it straight in my (the customers) defence. I will not rise any more.

[Theo]

You lot are completely buggering up the sale of my NVA A80s :lol:

[The Black Adder]

You lot are completely buggering up the sale of my NVA A80s :lol:

This was never to be an attack on Richard or his amplifiers but an observation, albeit an interesting event that happend to me of which was very, very rare in regards to any amplifier regardless of make.

Ask Doug Brady, with his 50 years experience he's only heard of just a handful of events such as this and most of those were in the 60's and 70's when amps and speakers were made for men. lol

[anthonyTD]

hi all,
the only thing i am going to comment on is the bit were Richard seems to want an argument with me now for simply agreeing with what others here have said:scratch:
as FOR conventional VALVE AMPS NOT BEING SAFE, well, one thing they will not do is pass DC and melt speakers, they have total isolation between the output valves and speakers due to having an output transformer which has seperate primary and secondary windings.
also, ALL the items i have built over the years have been done with safety in mind. the Soul amps which were well received world wide for their sonic abilities have surface mount fuses not only in the HT and opamp supplies but also in the bespoke class A Heater supplies.
also, there are fuses in the IEC sockets!
After everything thats been said here i dont realy understand why he has targeted me apart from my agreement with some of you on the safety aspects discussed here.
I understand his theory of why he dosent use safety fuses and have some empathy towards his findings in their apparent degaradation of sonics in some implementations, but i stand by my opinion that safety must come first when dealing with the genral public, and just adering to the basic regulations is not always enough.
It is posible to build equipment with excelent results while still mantaining the highest regard for safety.
The amps in question may have had an other type of component that Richard felt in his mind was adequit instead of a fuse where some fault situations occur, however, in this paticular situation, the components in question did nothing to prevent the catastrophic failier of the speaker due to excessive current being available, if there was high levels of music being played at the time then it would have been posible to burn out the speech coils in a similar way, but it was in the middle of the night that this situation arose where all ocupants were in bed asleep, so in my opinion, it must have been an amplifier failier due to either one or more of the output devices failing, or one of the power rails causing a massive DC offset at the speaker output, which in turn caused the speech coil to heat up to such a degree that it burnt, if the amp had had a DC offset detector it would have detected the fault and shut down the amp or at least the output stage.
If customers are made aware of the potential drawbacks of using such circuitry and accept the risk, then as long as Richards products adere to the current legislations, which they apparently do,then they are deemed to be fit for purpose, however, IMHO when you design such equipment it must be done with a concious mind.
Anthony,TD...

[jandl100]

You lot are completely buggering up the sale of my NVA A80s :lol:

My sympathies on that, Theo! :)

They really are great sounding amps, superb value for money, and I never had a moments bother from them when I owned your pair, which I bought new from NVA.

And in my fairly extensive experience, the customer service provided by Richard Dunn is not only second to none, but probably the best I have ever received on any product.

One major lesson from this thread, I think, is never to leave any amp on unattended.

[jandl100]

Question to the folks who actually know what theya re talking about on this thread ...

... What about modern amps that have a standby facility? - do concerns about amp reliability expressed here apply to amplifiers on standby as well?
Should I turn the damn thing off at the mains switch?

... actually, I guess I should just for eco-reasons!

[swampy]

I have often worried about direct coupled amps and valuable speakers. But fire hazard is another thought.


I've not had much luck with one protection board I fitted to my F5 which is direct coupled. At higher levels with dynamic music it would trip out as through over current protect was kicking in. I'd like to try and cap couple the output but not sure, need someone into power amp design who can confirm its ok to do so.

Also be aware that some directly coupled solid state pre-amps if they go faulty and output DC this then passes to the power amp and can cause another bigger problem. Most SS power amps have directly coupled inputs were a cap at the input would give DC input protection but with sonic consequences.

[anthonyTD]

Question to the folks who actually know what theya re talking about on this thread ...

... What about modern amps that have a standby facility? - do concerns about amp reliability expressed here apply to amplifiers on standby as well?
Should I turn the damn thing off at the mains switch?

... actually, I guess I should just for eco-reasons!
hi Jerry,
Most equipment in standby mode these days still draw a considerable amount of power, up to a third in some conditions, so with that in mind its always good practice to conserve energy.
Anthony,TD...

[WOStantonCS100]

Remember the good ol' Beatlesque days when Vox AC30's used to go up in flames almost regularly... Seems musicians, aware of the issue(s), didn't mind the potential hazards, knowing they would be rewarded with legendary tonality, and still don't! Bespoke replicas with the exact same circuit are built (and coveted) to this day. I've built a couple myself. I admit, I would never purposefully leave one on over night nor would I any amp, high end, guitar or otherwise. I mean, I'm not crazy. :eyebrows:

Perhaps we should just put an "Achtung" sticker on high end amps? "Great tone; but, may erupt into flames. Enjoy sonic bliss at your own risk" and just leave it at that. The odds of wifey setting the house ablaze in a kitchen fire (while awake and cognizant) are likely a lot higher. :lol:

[anthonyTD]

Remember the good ol' Beatlesque days when Vox AC30's used to go up in flames almost regularly... Seems musicians, aware of the issue(s), didn't mind the potential hazards, knowing they would be rewarded with legendary tonality, and still don't! Bespoke replicas with the exact same circuit are built (and coveted) to this day. I've built a couple myself. I admit, I would never purposefully leave one on over night nor would I any amp, high end, guitar or otherwise. I mean, I'm not crazy. :eyebrows:

Perhaps we should just put an "Achtung" sticker on high end amps? "Great tone; but, may erupt into flames. Enjoy sonic bliss at your own risk" and just leave it at that. The odds of wifey setting the house ablaze in a kitchen fire (while awake and cognizant) are likely a lot higher. :lol:
hi Biff,
some amps did indeed go up in flames but the main issue especialy with the original VOX amps was ventilation!
The circuits themselves were well designed, infact i have repaired/serviced many AC30's over the years so they cant have been all that bad.;)
Its true, valve amps in genral do run hot, its the nature of the beast, however, if the correct safety measures are implimented then they are as safe as any electrical appliance can be.
Its also true that you cannot safe guard against every eventuality, What you can do is safe guard against known faults, valve amps in genral when they develope known common faults usualy destroy themselves before anything else, When using Transistor amps [and OTL valve amps] on the other hand, extra care must be used in their design to protect ancilaries ie the speakers due to their direct interaction/connection.
Anthony,TD...

[docfoster]

My sympathies on that, Theo! :)

They really are great sounding amps, superb value for money, and I never had a moments bother...

Theo - hope this helps...
I can second the above quote.
I've owned NVA amps and whatnots for a few years. Never had any problems.
For whatever reasons, I have left them turned on. Probably havn't been off for than a total of a couple of weeks in 5 years.

Genuinely sorry to hear about the speaker fire. Glad that everyone was OK and that practically at least, things have worked out.

[Reid Malenfant]

C: The lids of the amplifiers were buckled and letting toxic fumes out.. so
:scratch: Am i reading this correctly?

What i mean is that the amp in it's natural state is in a totally sealed acrylic box? If so how on earth are the heatsinks cooled, i mean it must have some after all?

A class B amplifier is theoretically only about 78% efficient, allowing for component losses this drops to maybe 70%. So an 80W amplifier being driven hard will dissipate a lot of heat. Which needs to be gotten rid of to keep the transistors cool, but if there is no ventilation then how can they be kept cool? It must get like an oven in there :eek:

This just gets more crazy the more i hear.

However, I'm saying no more on the subject.

[spendorman]

:scratch: Am i reading this correctly?

What i mean is that the amp in it's natural state is in a totally sealed acrylic box? If so how on earth are the heatsinks cooled, i mean it must have some after all?

A class B amplifier is theoretically only about 78% efficient, allowing for component losses this drops to maybe 70%. So an 80W amplifier being driven hard will dissipate a lot of heat. Which needs to be gotten rid of to keep the transistors cool, but if there is no ventilation then how can they be kept cool? It must get like an oven in there :eek:

This just gets more crazy the more i hear.

However, I'm saying no more on the subject.

It's surprising just how much heat can be got rid of by radiation under these sort circumstances.

Years ago we needed a system that used a motor in a vented enclosure, to be sealed. We just got away with it. This was for an industrial floor cleaning machine.

What made a helpful difference, was moving the warm air around inside the sealed enclosure.

[anthonyTD]

hi all,
Acrylic is very good at losing heat, but anything housed in it that creates high levels of heat should always have alternative ways of disapating it!
i suspect that the cases used by Richard on the NVA amps do have at least ventilation slots for air circulation etc.
maybe he will confirm this.
Anthony,TD...

[anthonyTD]

hi all,
below the latest from Richard concerning me, i still dont get it, i never said his amps were bad sonicaly, i am sure they are very good in the right system, he has many satisfied customers, however, my obvious mistake was to chalenge him on the safety aspects of them.
Anyway, i dont see why he cant just hold his hands up and say Hey, ok, shit happens, this one went Tits up in a bad way, however, no one got hurt which is after all the most important thing, learn from it, and maybe re-think his policy on protection issues on future products, he's not going to like me for saying this but its my opinion, and he is of course welcome to come here and give his own on anything i write.
As far as his opinion on output transformers well, i'l leave that for another time.

Of course AnthonyTD has come back with weasel words. There was no criticism of his work at all, per usual he is twisting what has been said to his own benefit, yet he can attack my circuit and my designs with freedom. I am sure he makes very good amplifiers. It is very easy to say that his amps never go DC, well they can't as they have a bloody great big output transformer which wont pass DC (nor very low frequency bass notes). And those transformers have a greater detrimental sonic influence than any fuse or anything else you could put in the circuit.

I repeat, I feel he is being hypocritical because *NO* valve amplifiers will pass CE, his amp may be safe but they should not be on the European market for sale, and neither should a number of other things because companies just put a CE mark on, then write an essay on why they think they meet it, and file it away and forget about it, and some don't even do that, they just get the CE symbol printed on the back of what they make. IT IS NOT BEING ENFORCED! If it was you would not be able to buy any more valve amplifiers apart from second hand - full stop!

[alfie2902]

Hmmm.... What a surprise!! I never saw anything like this happening with Richards return :scratch:

I ran Exposure amps for a while, Farlowe ones with no zobal's & never had any problems at all. I used Ruark & Royd speakers with them & left them powered up all the time :eek: no fires here! Not sure how the NVA differ protection wise though as I've never owned any!

[Reid Malenfant]

hi all,
Acrylic is very good at losing heat, but anything housed in it that creates high levels of heat should always have alternative ways of disapating it!
i suspect that the cases used by Richard on the NVA amps do have at least ventilation slots for air circulation etc.
I have it on a good authority that the cases are sealed with zero ventilation slots or holes. Interestinly the heatsink doesn't even have the fins mounted vertically inside the case to at least get some form of air circulation going & aid heat removal from the heatsink itself. Though quite where it would go i have absolutely no idea :confused:

So we have an amp with just about zero protection with the properties of a slow cooker... Albeit a very nice sounding one :eyebrows:

:cool:

[Stratmangler]

I have it on a good authority that the cases are sealed with zero ventilation slots or holes. Interestinly the heatsink doesn't even have the fins mounted vertically inside the case to at least get some form of air circulation going & aid heat removal from the heatsink itself. Though quite where it would go i have absolutely no idea :confused:

So we have an amp with just about zero protection with the properties of a slow cooker... Albeit a very nice sounding one :eyebrows:

:cool:

I thought you were going to make no further comment.
http://theartofsound.net/forum/showpost.php?p=223101&postcount=206

[Reid Malenfant]

:lol: Yes but i had information pertinent to what was being asked ;)

So i gave it.

[WOStantonCS100]

hi Biff,
some amps did indeed go up in flames but the main issue especialy with the original VOX amps was ventilation!
The circuits themselves were well designed, infact i have repaired/serviced many AC30's over the years so they cant have been all that bad.;)
Its true, valve amps in genral do run hot, its the nature of the beast, however, if the correct safety measures are implimented then they are as safe as any electrical appliance can be.
Its also true that you cannot safe guard against every eventuality, What you can do is safe guard against known faults, valve amps in genral when they develope known common faults usualy destroy themselves before anything else, When using Transistor amps [and OTL valve amps] on the other hand, extra care must be used in their design to protect ancilaries ie the speakers due to their direct interaction/connection.
Anthony,TD...

See, that's kind of what I'm getting at. It would take extraordinary measures to safe guard against every eventuality (or remote possibilities). I could not have said that any better. "Safe as any electrical appliance" realistically should be no comfort to anyone, especially in this day and age. ;)

In the case of Vox, it would seem silly to have forced them to install a chassis fan in all of their amps though it would have kept things cooler. (Eventually, they did widen the vents; still no fan.) I would imagine any added fans, back then, that could have been added would have also added... ...noise.

I am no expert on transistor amps. Fixed a few; but, never built one from the ground up. However, I can believe that there are trade offs in implementation when it comes to circuit (the sound) and "safety". I guess that's for the transistor gurus to squabble over. I do think the responsibility for safe operation relies in more than one area, as it pertains to this situation and I don't think it all lays at the feet of NVA. No offense; but, not stacking power amps, or at least providing adequate ventilation of a power amp should be a given. When it's a common sense thing, I don't see why it has to be spelled out with stickers. Should NVA consider added safety measures? Maybe; but, maybe not if it significantly affects the sonics of their product, especially given that this seems to be quite a rare occurrence. Should the speaker manufacture seriously consider using less inflammable materials? I would say absolutely, especially if there is a better than average chance that their drivers will go up in flames when overloaded.

[anthonyTD]

See, that's kind of what I'm getting at. It would take extraordinary measures to safe guard against every eventuality (or remote possibilities). I could not have said that any better. "Safe as any electrical appliance" realistically should be no comfort to anyone, especially in this day and age. ;)

In the case of Vox, it would seem silly to have forced them to install a chassis fan in all of their amps though it would have kept things cooler. (Eventually, they did widen the vents; still no fan.) I would imagine any added fans, back then, that could have been added would have also added... ...noise.

I am no expert on transistor amps. Fixed a few; but, never built one from the ground up. However, I can believe that there are trade offs in implementation when it comes to circuit (the sound) and "safety". I guess that's for the transistor gurus to squabble over. I do think the responsibility for safe operation relies in more than one area, as it pertains to this situation and I don't think it all lays at the feet of NVA. No offense; but, not stacking power amps, or at least providing adequate ventilation of a power amp should be a given. When it's a common sense thing, I don't see why it has to be spelled out with stickers. Should NVA consider added safety measures? Maybe; but, maybe not if it significantly affects the sonics of their product, especially given that this seems to be quite a rare occurrence. Should the speaker manufacture seriously consider using less inflammable materials? I would say absolutely, especially if there is a better than average chance that their drivers will go up in flames when overloaded.

hi Biff,
Good points, and very thought provoking, there are probably lots of transistor amps out there with similar output stages that have no protection and as you say it is down to the discretion of the designer, if they feel that certain protection circuits will be detremental to the overall sonic performance of the amplifier, and decide not to implement any then thats fine, however, they should IMHO make it absolutely clear to the end user that there is a higher risk of damage to the unit and anciliries without it.
just a clear description of the circuit, and how it works in the instruction manual supplied would suffice.
The responsibility would then fall partly on the consumer to adere to any special requirements needed to keep himself and the equipment safe.
Anthony,TD...

[Reid Malenfant]

hi Biff,
Good points, and very thought provoking, there are probably lots of transistor amps out there with similar output stages that have no protection and as you say it is down to the discretion of the designer, if they feel that certain protection circuits will be detremental to the overall sonic performance of the amplifier, and decide not to implement any then thats fine, however, they should IMHO make it absolutely clear to the end user that there is a higher risk of damage to the unit and anciliries without it.
just a clear description of the circuit, and how it works in the instruction manual supplied would suffice.
The responsibility would then fall partly on the consumer to adere to any special requirements needed to keep himself and the equipment safe.
Anthony,TD...
Anthony i have never heard of any DC coupled amplifier with no protection circuits, until this came along.

At the minimum a fuse is generally fitted to the output, if not that then either a capacitor or far more generally a relay with DC offset sensing that opens the relay when a fault occurs.

In all honesty speaker manufacturers shouldn't ever need to worry about high power continuous DC feeding a woofer voicecoil as i'm pretty sure like myself that they assume all amps are pretty well failsafe (as they should be) & 99.99% are.

What we have here is the 0.01%


Just so i'm not appearing to be negative all the time i can understand why it's good sonically to have nothing following the output stage. A Relay does as add resistance due to the contacts. However these days there is a way round this. Modern power mosfets have incredibly low Rds on & these could be used instead of a relay as long as they are connected back to back via there sources. This is what i intend to do myself using some 75V mosfets (which should be good for a 350W RMS amp 8 ohm), the type i have have an Rds on of less than 2.7 milliohm. If i use 4 of these which only cost about £1 each i'll have the equivalent of a relay with a contact resistance of less than 2.7 milliohm, which is vanishingly small ;) The current rating in this case would be 250A continuous!

[YNWaN]

hi all,
Acrylic is very good at losing heat

Not really, in fact it is rather a good insulator:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Thermal conductivity:

Acrylic = 0.2

Aluminium = 250

Which is why there are no heatsinks made from acrylic.
__________________

My own Naim amplifiers monitor the temperature of the heatsink (an aluminium one) and turns the amplifier off if the temperature rises too much.

[Joe]

This was never to be an attack on Richard or his amplifiers but an observation, albeit an interesting event that happend to me of which was very, very rare in regards to any amplifier regardless of make.

Ask Doug Brady, with his 50 years experience he's only heard of just a handful of events such as this and most of those were in the 60's and 70's when amps and speakers were made for men. lol

It happened to me with one of those Nytech amps with sliding controls. I think it was shorting at the speaker outputs; they were on the flimsy side. Some of the early Musical Fidelity amps were also known to spontaneously combust ....

[spendorman]

Not really, in fact it is rather a good insulator:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Thermal conductivity:

Acrylic = 0.2

Aluminium = 250

Which is why there are no heatsinks made from acrylic.
__________________

My own Naim amplifiers monitor the temperature of the heatsink (an aluminium one) and turns the amplifier off if the temperature rises too much.

Yes, but we use Mica (with poor thermal conduction) to electrically insulate transistors from heatsinks. It works, because a thin layer is used.

[Reid Malenfant]

Yes, but we use Mica (with poor thermal conduction) to electrically insulate transistors from heatsinks. It works, because a thin layer is used.
I don't, i use Aluminium Oxide ;) Vastly superior to Mica!

[anthonyTD]

Not really, in fact it is rather a good insulator:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Thermal conductivity:

Acrylic = 0.2

Aluminium = 250

Which is why there are no heatsinks made from acrylic.
__________________

My own Naim amplifiers monitor the temperature of the heatsink (an aluminium one) and turns the amplifier off if the temperature rises too much.

hi Ynwan,
what i was getting at is, acrylic dosent hold heat very well due to as you say being more an insulator than conductor!
hope that makes sense.
Anthony,TD...

[anthonyTD]

Anthony i have never heard of any DC coupled amplifier with no protection circuits, until this came along.

At the minimum a fuse is generally fitted to the output, if not that then either a capacitor or far more generally a relay with DC offset sensing that opens the relay when a fault occurs.

In all honesty speaker manufacturers shouldn't ever need to worry about high power continuous DC feeding a woofer voicecoil as i'm pretty sure like myself that they assume all amps are pretty well failsafe (as they should be) & 99.99% are.

What we have here is the 0.01%



Just so i'm not appearing to be negative all the time i can understand why it's good sonically to have nothing following the output stage. A Relay does as add resistance due to the contacts. However these days there is a way round this. Modern power mosfets have incredibly low Rds on & these could be used instead of a relay as long as they are connected back to back via there sources. This is what i intend to do myself using some 75V mosfets (which should be good for a 350W RMS amp 8 ohm), the type i have have an Rds on of less than 2.7 milliohm. If i use 4 of these which only cost about £1 each i'll have the equivalent of a relay with a contact resistance of less than 2.7 milliohm, which is vanishingly small ;) The current rating in this case would be 250A continuous!

Hi Mark,
i totaly agree with your aproach on the DC detection circuit idea above,
things have moved on dramaticaly since the early years of transistor amp technology, and as you say the components to build such circuitry are as cheap as chips.
DC detection or current sensing circuitry IMHO need not affect or interfere in anyway with the sonics of an audio amplifier when the right circuitry and devices are used.
Anthony,TD...

[spendorman]

I don't, i use Aluminium Oxide ;) Vastly superior to Mica!

OK, but aluminium oxide is still a pretty poor conductor of heat.

I can't quote figures from memory.

Strangely, my work at that big Aerospace company had a lot to with conducting heat through thin layers of materials with fairly poor coefficients of thermal conduction.

Thin films were often vacuum sputtered. This was one of my specialities.

There was often a problem conducting heat away from special circuits that were Ion Beam Milled. I developed a process for this that used a thin layer (that was not a particular good heat conductor). It worked.

[Reid Malenfant]

Not really Anthony. In this case with a sealed box what you'd need is something very thermally conductive to transfer the heat inside to the outside & radiate it off. As Acrylic looks to be a worse conductor than slate or marble it looks like a very poor choice of material for keeping the electronics cool inside the casing due to it being sealed ;)
..

[Reid Malenfant]

OK, but aluminium oxide is still a pretty poor conductor of heat.
Look on the link that Mark provided ;)

Mica 0.71, Aluminium Oxide 30!

[spendorman]

Look on the link that Mark provided ;)

Mica 0.71, Aluminium Oxide 30!

Aluminium 250

[Reid Malenfant]

Aluminium 250
:lolsign: Yep, but i'd rather have 2mm of aluminium oxide between my power transistors & heatsink than 0.2mm of mica :)

Besides which there will be far less capacitive coupling between the two which can have sonic benefits ;) Depending on the circuit of course... Either way though the aluminium oxide is better than mica at the end of the day.

[spendorman]

:lolsign: Yep, but i'd rather have 2mm of aluminium oxide between my power transistors & heatsink than 0.2mm of mica :)

Besides which there will be far less capacitive coupling between the two which can have sonic benefits ;) Depending on the circuit of course... Either way though the aluminium oxide is better than mica at the end of the day.

lol

I'm glad to get away from Aluminium Oxide (Alumina). 20 years of development work with it (Microwave Integrated Circuits). It's so prone to fracture.

Now, I use to coat Alumina with Nichrome/Gold/ Copper, that ended up a good heat conductor! lol

I suppose, the important thing is that strange things can work if the engineering/ physics is right.

[Reid Malenfant]

Now, I use to coat Alumina with Nichrome/Gold/ Copper, that ended up a good heat conductor! lol
Wouldn't that defeat the point of electrical insulation though?

Yes, Alumina does tend to chip easily if handled incorrectly i must admit, it's like ceramic stuff at the end of the day ;)

[anthonyTD]

Not really Anthony. In this case with a sealed box what you'd need is something very thermally conductive to transfer the heat inside to the outside & radiate it off. As Acrylic looks to be a worse conductor than slate or marble it looks like a very poor choice of material for keeping the electronics cool inside the casing due to it being sealed ;)
..
hi mark,
i think we have a miss-understanding,:doh: i totaly agree that acrylic is of no use for conducting heat away from hot items or surfaces, what i was getting at is,due to its properties it is very unlikely for the heat inside the unit to cause the acrylic to ignite and thus cause further damage.
Anthony,TD.

[Reid Malenfant]

hi mark,
i think we have a miss-understanding,:doh: i totaly agree that acrylic is of no use for conducting heat away from hot items or surfaces, what i was getting at is,due to its properties it is very unlikely for the heat inside the unit to cause the acrylic to ignite and thus cause further damage.
Anthony,TD.
Hi Anthony, yep 100% agreed as the transistors would be slag before the Acrylic got to self ignition temperature :eyebrows:

It might make a rather interesting shape though, maybe Tracey Emin could use it for art? :scratch: :eyebrows:

All the best chap :)

[spendorman]

Wouldn't that defeat the point of electrical insulation though?

Yes, Alumina does tend to chip easily if handled incorrectly i must admit, it's like ceramic stuff at the end of the day ;)

As an electrical insulator, yes it's pretty good, unless cracks develop which can cause all manner of problems.

We sometimes sputtered alumina.

Back on to power amps passing heavy DC, I think that I mentioned previously that the original Quad 405 had nothing on the output stage to prevent this under fault conditions. As an afterthought, a crowbar circuit was added on a small board mounted on the back of the speaker connection posts.

[Reid Malenfant]

Back on to power amps passing heavy DC, I think that I mentioned previously that the original Quad 405 had nothing on the output stage to prevent this under fault conditions. As an afterthought, a crowbar circuit was added on a small board mounted on the back of the speaker connection posts.
Yes, i have two of them :) That is two 405 with the protection you mention ;)

The crowbar was designed to blow the fuses in the DC lines, good enough.

[spendorman]

Yes, i have two of them :) That is two 405 with the protection you mention ;)

The crowbar was designed to blow the fuses in the DC lines, good enough.

I failed to mention that even the original 405 had the fuses in the DC lines. But the amp was criticised in a magazine test report and later production had the crowbar protection fitted.

My 405, bought new by me in 1976, had the crowbar protection as purchased. So I suspect that not many were produced without protection.

The 405 is a 405-2 now, converted by me about 1987.

[Reid Malenfant]

Hi Mark,
i totaly agree with your aproach on the DC detection circuit idea above,
things have moved on dramaticaly since the early years of transistor amp technology, and as you say the components to build such circuitry are as cheap as chips.
DC detection or current sensing circuitry IMHO need not affect or interfere in anyway with the sonics of an audio amplifier when the right circuitry and devices are used.
Anthony,TD...
Just thought i'd bring this up again. With the kind of circuitry i'm planning on the output could be disconnected within less than a few hundred nano seconds of a fault condition being recognised. Unlike a big relay that may take up to twenty milli seconds or more to break the circuit. So at least 1000 times faster! Now while i very much doubt that it will have any significant effect on bass driver longentivity due to faults in the power amp (that is down to the time constant detecting any fault) it sure as hell is going to perform better & provide much better safety for the speaker.

[southall-1998]

I failed to mention that even the original 405 had the fuses in the DC lines. But the amp was criticised in a magazine test report and later production had the crowbar protection fitted.

My 405, bought new by me in 1976, had the crowbar protection as purchased. So I suspect that not many were produced without protection.

The 405 is a 405-2 now, converted by me about 1987.

Sorry for my silly question. How much was the 405 new in 1976?

Regards.

[spendorman]

Looking back at my posts about the 405. Around the mid 1970's, Quad thought that a crowbar protection circuit was needed, so we surely need something as good as that or better today.

[spendorman]

Sorry for my silly question. How much was the 405 new in 1976?

Regards.

Now, you are asking, that is taxing my memory lol. It was a fair amount of money for me, think it was around £160. I remember popping out from work at lunchtime to get it. Felt guilty spending so much!

In fact, bought not a million miles from you, Wembley.

A few years later, felt guilty again, bought a new Quad 44, that was over £200. I have both receipts somewhere.

Both units are still close to mint.

[jandl100]

hi all,
Acrylic is very good at losing heat, but anything housed in it that creates high levels of heat should always have alternative ways of disapating it!
Anthony,TD...

For the record, with my old NVA A80 mono power amps the acrylic case got 'gently warm' over much of its top surface. So it was clearly capable of losing a fair bit of heat by radiation/convection.

[anthonyTD]

For the record, with my old NVA A80 mono power amps the acrylic case got 'gently warm' over much of its top surface. So it was clearly capable of losing a fair bit of heat by radiation/convection.
hi jerry,
the point is, acrylic is not very good at drawing heat out into itself, so while the acrylic may only feel warm, the components inside could well be a great deal hotter!
my own soul power amps have all-acrylic covers, but because everything is heatsinked they hardly ever get warm, but they also have very quiet fans in key areas, blowing air up through the boards and over the valves to aid air circulation.
Anthony,TD...

[spendorman]

Sorry for my silly question. How much was the 405 new in 1976?

Regards.

I still think that I paid around £160, have not found receipt.

In a 1976 magazine, Herts Hi Fi advertise it for £143.75

Found some Quad price lists:

http://farm4.static.flickr.com/3396/5818087588_51df22ba73_b.jpg

http://farm3.static.flickr.com/2628/5817518907_be56f5c063_b.jpg

[barry-potter]

unless you know what the actual design of an nva power amp is you lot are just pointlessly ponificating.

[Marco]

Ok, guys, I've been a little busy recently, and so have been looking through some of the recent posts since I was last active on this thread, and whilst some good points have been made, I feel that there has been the tendency for some to adopt a bit of a 'witch hunt' against NVA - or at the very least, somewhat over-emphasise an isolated incident of their amps causing fires, or any likelihood of such.

Therefore, I think that it is necessary to apply a little perspective and reality, which I feel Richard's recent remarks on his forum ably provide:


I have been producing amplifiers for over 30 years and for over 10 years using Class 2 regs so if his crap and libel was true do you realy think I would still be in business, if every amplifer is going to fail and set fire to the loudspeaker do you really think I would be in business, if the case design stopped the amp removing heat and frying the amp do you really think I would still be in business. Well as I have repeated over an over again, that specific event is the only similar event that has happened in over 30 years and over 2 or 3 thousand amplifiers, I am afraid that speaks for itself.


Indeed. Remember that this is simply ONE incident which has occurred in over 30 years of NVA building amplifiers. I am quite certain, given the specialist nature of these amps, and the fact that the enthusiast's market is a very small world, that if there had been any more similar incidents, we'd have heard about them by now! So let's give it a rest.

Mark, having made your point now (and indeed hammered it home), I must ask you to get off of Richard's case and honour your promise of making no further comments to this discussion in reference to Richard or the design of his amps. Otherwise I will remove them, as your dispute with him has now run its course.

I would also ask, in terms of everyone else's contributions here, that the discussion now moves away from any unnecessary reference to NVA amps, or Joe's now 'notorious' incident, and onto more general observations about amplifier safety protection.

Cheers, chaps! :cool:

Marco.

[Dr Bunsen Honeydew]

Thank you for that Marco - in which case I will try again, why should I let the bastards win and get what they want - me not being here!

[Marco]

You're welcome, Richard - fair's fair, and all that. But also remember to try and react less aggressively to any well-intended constructive criticism :)


why should I let the bastards win and get what they want - me not being here!


As in the well-known quip 'don't let the bastards get you down', I presume, rather than a derogatory reference to any of our members being "bastards"? ;)

Marco.

[WOStantonCS100]

BTW: I loved the clip of "miiiiiii miiiiiiiiiiiiiiiiii". :lolsign:

[Dr Bunsen Honeydew]

I anyone is worried about an amplifier overheating or being left on then use one of these. http://shop.ebay.co.uk/i.html?_from=R40&_trksid=p5508.m570.l1311&_nkw=laptop+cooling+pad&_sacat=See-All-Categories The fan based ones can be a bit noisy depending on make and construction and usually take power from a USB socket, but there are some mains ones. The chemical based ones are obviously silent but less effective.

[Slippershod]

BTW: I loved the clip of "miiiiiii miiiiiiiiiiiiiiiiii". :lolsign:

almost Sinatra-like phrasing, dontcha think? :respect:

[swampy]

As in the well-known quip 'don't let the bastards get you down', ;)

Marco.

yes, that well known Latin phrase which maybe nonsense ...
Illegitimi non carborundum

[Dr Bunsen Honeydew]

almost Sinatra-like phrasing, dontcha think? :respect:
None of them beat this one and it is a good recording too.

http://www.youtube.com/watch?v=tgbNymZ7vqY