Aye, a FRED :eyebrows: They'll do nicely ;)
In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple ;)
Aye, a FRED :eyebrows: They'll do nicely ;)
In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple ;)
Yes, as said those will be fine. The confusion was that they are not schottky
But I just noticed that RS now stock the Cree high voltage schottky diodes.
http://uk.rs-online.com/web/search/s...duct&R=7027453
I must give them a try.
Awesome, thanks Mark.Quote:
Originally Posted by Reid Malenfant
I was thinking the same thing with the caps. C1 had already been swapped for a 220uF so I might use a similar capacity to remove extra ripple over the standard 100uF. It's mainly C2 and C3 I can't decide on. I've heard C3 has a bigger impact on the sound than the other two and that a film cap should work well but that would seriously limit the capacity I could use due to space and cost restrictions. Do you have any recommendations on what caps to use in those positions?
My other idea is to use some smaller film caps (maybe around 3uF) after C3, one for each Channel of the amp as close to point B on the schematic as possible. My idea is that it would provide small energy supply close to the area of demand to smooth things out. What do you think to that idea?
Cheers. :cool:
I'm not sure i'd change the value of C3 very much if at all ;) It appears that it's just being fed by a resistor & the circuit along with another bleeding resistor looks to be maintaining a fairly stable DC for the front end. You could bypass the 100uf with something of better quality or go the whole hog & regulate the front end with a discrete voltage regulator using a power Mosfet. As i say though, looking at it as is i'd keep to around 100uf.
That leaves you with C1 & 2, as i have already mentioned C1 will have the largest ripple voltage so that to my mind is the one to focus on in the way of chucking capacitance at it. C2 should be worth bypassing as it directly feeds the output stage..
Just remember i know diddly squat about valves though :eyebrows:
Dave, just MHO, the Mundorf silver oils are quite good, but I found them a little too much at the top end. If you are prepared to spend a few quid, I'd go for either SCR teflons or AN coppers. These two are the best I've tried so far.
Ok, thanks Mark. What would you use for bypassing C2?Quote:
Originally Posted by Reid Malenfant
Thanks Ali. I'm slightly worried about the Silver/Oil's sound too bright. I think some people perceive them that way while others think they sound detailed and airy. I guess it also depends on what they're used in. I decided it was worth the risk as they're pretty much at the top of my price range. I've already spent about the same on components as I did on the amp, so I'd prefer not to go any further. I've heard the standard Mundorf Supreme version sounds similar to the Silver/Oil but a bit less bright, so that's a possibility. I was just a bit worried that with the Kiwame resistors and the the warmer sounding caps that I'd end up too much warmth. I guess I'll have to wait and see if my theory works in practice. :)Quote:
Originally Posted by Ali Tait
Some kind of high voltage Polypropylene or similar film capacitor :) Depending on what you can fit in i'd go for 0.47uf or bigger if possible. 500V DC rating or higher to be on the safe side :eyebrows:
Thanks Mark. I might look at getting some Solen FastCap's to experiment with bypassing. Or maybe some Evox-Rifa Pulse caps. :hmm:I'll have to check on the dimensions.Quote:
Originally Posted by Reid Malenfant
Dave, I've found the Takman resistors very good. Cheap too.
I'd go for the Solens out of the two, they are a little more specialised where as the Evox-Rifa are more general purpose as far as i'm aware ;)
I'm sure there are a bucket full more out there though so take your time. Whilst it won't have any audio signal passing directly through it it still one of the most important caps in the amp keeping the voltage on the front end stable.
Thanks Ali. I've used them before and found them to be good. I'm actually using a couple in this project as I couldn't get Kiwame's in a certain value. I'm also using some tantalum resistors in another place for the same reason.Quote:
Originally Posted by Ali Tait
Thanks Mark. I've ordered some 0.6uF Solen caps as they were the biggest that would fit on the back of the PCB. I think they'll be easier to fit than the Evox ones as well.Quote:
Originally Posted by Reid Malenfant
I've now got all of the components mounted other than the few power supply related caps that I'm ordering now and the parts relating to the heater supply. The heater supply is proving tricky as there's not much room to mount the extra components required for the Schottky diode upgrade. So I'm just trying to puzzle that out. I'll post some photo's ASAP but I seem to have mis-placed my camera at the moment. :doh:
I found my camera last night, so here's a photo of what I've done so far:
http://i2.photobucket.com/albums/y48...L84_PCB_01.jpg
I've now installed the DC heater supply parts and wired up the AC heater supply. As you can see the PCB is getting rather busy. All the components I've used are physically larger than those they replaced which has presented some challenges. The DC heater supply was particularly tricky which this photo attempts to show:
http://i2.photobucket.com/albums/y48..._Heater_01.jpg
I've used 4700uF Rubycon YXF high ripple, long life caps for the DC heater. I wrapped these in heat shrink to prevent shorts caused my the tight packaging. I just hope I've wired this bit up correctly. I've tried to make it so it's not too tricky to swap the resistor just in case I need to tweak the value to get 6.3V.
Here you can see how the brown Elna Silmic II electrolytic and black Mundorf axial cap's on the right are much bigger than the spaces on the PCB which forced me to do some stacking and packing. You can also see how I've directly soldered a grid resistor to the valve base to get it as close as possible. I've done the same thing with all the grid resistors.:
http://i2.photobucket.com/albums/y48.../Tight_Fit.jpg
I've now ordered the last few caps I need. I'll be using a 220uF Panasonic high ripple cap in position C1 and 100uF Vishay low ESR caps in position C2 and C3. So while I'm waiting for them to arrive I've started some work on the case and cabling related stuff. I've removed the input selector, volume control, input sockets and speaker binding posts. I'm going to fit a pair of WBT Nextgen copper RCA sockets for the input and some Eichmann Tellurium Copper speaker binding posts. I'm also upgrading the Zobel network components to Mills wirewound resistors and Mundorf Supreme caps which will be soldered directly to the back of the binding posts. All the internal wiring will be replaced too. Probably with 5N silver wire in Teflon sheathing but I've not quite decided yet. That's all for now. :)
Have you tried Ampohm oil paper caps? They appear to be going for good prices at the moment and have a big selection including copper.
I did consider them early on but I guess they didn't score as highly as the Mundorf Silver/Oil's in the reviews I read so I discounted them. There are so many makes and models out there I'll probably never try them all. I'm fairly new to DIY Hi-Fi, so as I've not tried many makes I'm quite reliant on recommendations I read online. I guess eventually as I try more I'll settle on on some favorites.Quote:
Originally Posted by colinB
Have you compared the Ampohm's against any other caps?
I havent Dave. There is a mod for my tube amp but it involves Jensen caps and they cost a bomb. Always looking for a cheap oil/paper alternative.
All the parts I was waiting for arrived earlier this week and I managed to finish building the amp back up tonight. After a thorough check over to make sure I'd not made any obvious errors I fired her up to check some voltages. No bangs, no smoke and I didn't get electrocuted, so it's all good so far! :eyebrows: Some voltages seem a bit high, some a bit low but hopefully they're within tolerance. I'll have to check that out further but for now it seems to be working. So I'm going to tidy all the crap off my workbench (or "the dining room table" as my wife calls it :lol:) and hook the amp up to some cheap speakers for the first listening test. I'll then break out the oscilloscope and check out some waveforms. I'll try and take some photos too. They're jobs for tomorrow though. Now it's time for a beer, then bed. :cool:
Well it makes sound. :champagne:
I can't really tell what the sound quality is like yet as the £10 Argos speakers I use for testing are offensively crap. I'm going to leave it running through them for at least a couple of hour just to make sure the amp seems stable. I'll then take a few photos and hook the amp up to my main system. :)
Yes please to pics.
I do have to say that after listening to the Albarry power amps the other day, I should confirm that solid state CAN do it with careful design and a beefy power supply - not to get oodles of Watts, but to put some inertia behind the Watts that DO come out, if you see what I mean. Hobby-ists that can make their own (valve) gear using good circuits and components for not too much dosh can grin from ear to ear IMO :)
I know what you mean and I've come to the same conclusion. The power supply seems to play a massive role in determining the end results. My 550W solid state mono-blocks sound great to me but the tiny 15W KEL84 in bottom of the range spec sounded almost as good overall and better in some areas. So I really can't wait to here what it sounds like with all the power supply and signal path mods I've done. :eyebrows:Quote:
Originally Posted by DSJR
As requested, here are a few photo's of the amp:
http://i2.photobucket.com/albums/y48..._Testing01.jpg
The bottom box is my old MD player that's currently looping Jamiroquai. The box at the back is my Lighter Note passive attenuator. The blue LCD is a mains voltage display that I got off eBay recently. It's been calibrated with a Fluke meter that can just be seen in the bottom right.
I couldn't resist doing a valve glow closeup. It'll look better at night but never quite as impressive as the bigger output valves like KT88's. Oh well, they still looks nice and are chucking out a fair amount of heat, as is the mains transformer. This has been mounted of some silicon bushes that I made to raise it up a bit to allow better air flow and dampen the slight hum it makes. The hum has definitely been reduced, so I'm happy about that as this was one of my only real criticisms of the amp. The valve dampers were bought of ebay and seem very good quality even if they do look a bit daft.
http://i2.photobucket.com/albums/y48..._Testing02.jpg
http://i2.photobucket.com/albums/y48..._Testing03.jpg
Once the amp's been running for another hour or two I'll let it cool down so I can take some photo's of the inside. :cool:
EDIT: I forgot to mention that I've left the front panel off for now. I need to sort it out so I can mount the control knobs back on to preserve the aesthetics. The knobs won't actually control anything as the amp's been converted to a single input power amp.
EDIT2: I probably ought to apologise for the blue power LED that I fitted. The original was an orange one that just didn't match my other equipment that all came with blue LED's. I know some people hate them but you can't please everyone. :ner:
I've just checked for audible hum and hiss and I can't hear any hum and just a slight bit of hiss when the volume is cranked all the way up. So I'm happy with that.
The only slight cause for concern so far is that the mains transformer is almost too hot to touch. I've read that they run hot in the KEL84 but I'd prefer to lower the temp if possible. Does anyone know if attaching heatsinks to the transformer sides with heat conductive epoxy will affect the working of the transformer at all? I wouldn't have thought so as aluminium isn't ferrous but I thought I better check to be on the safe side. Cheers.
That'll be fine Dave, though it's the windings that you want to keep cool really ;)Quote:
Originally Posted by HighFidelityGuy
Ok thanks Mark. I might look into that later.Quote:
Originally Posted by Reid Malenfant
It looks like I spoke too soon about hum. I've just connected the amp up to my main speakers and I get a hum through both channels. :( I guess the cheapo Argos speakers weren't sensitive enough to pick it up. So I need to look into that issue. It sounds like it's about 100Hz, so I don't know if that's anything to go on. :scratch: I've got a feeling it's going to be either the signal input wiring or the feedback wiring that's at fault. The original wire was shielded but I've used twin solid core twisted together. So perhaps it's picking up interference from one of the rectifiers or something. :scratch:
Try using shielded wire where it was used previously, it was probably used for a reason :)
Ok thanks. I always struggle to find good quality but reasonably priced wire to use for internal hookup. We spend tons of money on good quality cables to go between equipment so it seems only sensible to use cables of the same quality inside equipment. It would be great if Mark Grant sold his G1000HD cable unterminated as I'd use that. Up until now I've not had a problem using 5N silver wire off eBay but I guess this amp creates more EMI than other things I've worked with. It could just be a wire routing issue though. I had to run the left channel feed back wire quite close to the heater supply rectifier as I ran out of cable.
I've tried moving the input wire further away and that hasn't helped so It might be the feedback wire. It's going to be a real pain to get to the place on the PCB where this connects now so I think what I'm going to try first is sheathing the existing cable from the other end. I have some shielded microphone cable that I should be able to strip the internal cores out of. I'll try that and report back in a bit....
So i'm guessing you haven't PM'd him to find out if he would then :scratch:Quote:
Originally Posted by HighFidelityGuy
Don't ask & you certainly won't get :eyebrows:
He's a nice chap to deal with & after a bit of discussion supplied me with 20M (i think) of unterminated DSP 2.5 mains cable ;)
I get wonderful results from van damme screened cables. The single double screened has a handful of silver strands in it from memory and this seems to work well. The wire costs less than £1.50m and is really good - honest!
I've not asked Mark. I decided to just use what I had seen as I'd had good results before. I'll send him a PM and see what he says.Quote:
Originally Posted by Reid Malenfant
Thanks, I'll keep that in mind. :)Quote:
Originally Posted by DSJR
Well I tried shielding the existing cable and that didn't work. There wasn't enough room inside the microphone cable. So I decided to just use the microphone cable for the feedback wire. Unfortunately it hasn't changed anything. So I need to try something else. First I'm going to do some searching on the Word Design forum to see if anyone else has had a similar problem.
Aaaaaaaarrrrgggg, I don't believe it, I think I've just wasted ages replacing the feedback wire when there was nothing wrong with the amp. :steam::doh:
I decided to double check that the hum wasn't being caused by a ground loop, so I started pulling out cables going into my attenuator and when I got to the one that comes from my AV amp the hum disappeared. So it was a fecking ground loop all along. :steam: What a ball ache. :rolleyes:
I've got an idea how to fix this by plugging the AV amp into a different socket but for now it's staying unplugged the fecking fecker. Right I'm off to Burger King for a belated dinner as I can't be arsed to cook.....
I've now lived with my modded KEL84 for a few days and I must say that I'm really enjoying the sound it's making. I didn't do any critical listening for the first couple of days but during that time it sounded very good but a bit uneven, with a slightly bright top end and slightly too much mid-bass punch. These areas have now calmed down and the overall sound seems very balanced. I haven't done any direct A/B test between this amp and my solid-state mono-blocks but I had become quite accustomed to the solid-state sound. It seems at the moment that I can hear more detail through the KEL84, with the main improvement being that there seems to be more space around the notes, as if they were getting blended together a bit more by the solid state amps. This has produced a more airy sound that I like a lot. Bass is also improved, with a nice mid-bass punch and seemingly more control and clarity in the lower bass. The mid-range also seems clearer somehow which has made vocals slightly more realistic sounding. Overall the sound seems to be more detailed and even handed and just generally easier to listen to. Which is nice.
So the upgrades seem to have filled the main gaps I was hearing between my solid-state amps and the un-modded KEL84. Hopefully this really is the case and it's not just that I'm making myself believe it. :doh: I'll know better when I get one of Stan's switch boxes to do some proper A/B testing. I'll leave that for a while though so the KEL84 can run in a bit more. I think I'll have to look into getting some better EL84's to try as well. :eyebrows:
I've really been surprised by just how much performance the KEL84 has to offer. I never thought a 15W valve amp could work this well with my speakers. Especially in the bass department. I thought 15W would be way too little to get this much bass but I was very wrong. :eek:
Does the mains transformer still run very hot?
I tried the top models Graaf preamp at home a good few years ago (the sample KK wet himself over). On switch-on, the transformer buzzed like a swarm of angry bees, but was silent 20 minutes later. The thing was, that he casework got very hot and I really feared for the row of expensive oil-filled capacitors visible along the back of the case. A few years of regular baking this way must have shortened their lives I'd have thought.
Yep, the mains transformer still runs rather hot. It must reach over 40 degrees C. I've ordered an infrared thermometer so I can make some proper readings. I do however seem to have cured the mechanical buzzing the transformer made by mounting it on silicon bushes. I think I'll try attaching some heatsinks to it but it'll be a but tricky as the sides aren't flat.
Other than the hot transformer, the only negative thing I've been able to think of with the amp is that the power LED is too bright. I was just going to add an extra resistor but I think I might connect a pot in series instead and mount this where the volume pot went. I need to mount something there anyway to fill the hole so I may as well give it a purpose. :)
I had my first experience of valves last night.My friend has very kindly loaned me a Art Audio pre/power combo.Had a really good listen to it last night and was very impressed.I am a tad obsessive about sibilance and have pointed the finger at everything apart from my naim5i amp.The valve combo was much more forgiving.Female vocals are fantastic,symbals sound lovely.I was suprised at the lovely bass.I listen to a lot of rock and found the combo lacked some of the attack of the naim but overall a far less fatiguing sound.Iam quite interested to hear what a combination of valves and ss would sound like.
I'll bring my Croft and Copper amp with me, Tony, next time I'm coming up to Glasgow, and you'll be able to hear both combinations :)
Marco.
Lord help me....This could get awfy expensive.....
Lol - it'll give you an 'interesting' benchmark from which to judge.... :eyebrows:
Marco.
Marco,
Thanks for the offer,Id be delighted to have you over.Ill make yer tea and provide plenty of red to wash it down.Let me know whenever your planning to come back home.
No worries, dude. It'll be next time I'm up visiting Snapper, whom I think you should also meet, as (like me) he was born just around the corner from you :)
Marco.
ANYTHING compared to mid-period Naim is going to sound more laid back and refined IMO...
I repeat, Glenn Croft's new integrated (£1K inc phono stage) will sound just what you'd need - the atmosphere and 3-D of good valves, with some control and power from solid-state. A highly addictive combination IMO... and the new control knobs make it look far more expensive than it actually is IMO.
Yep, the new Croft integrated is a fine sounding amp. And agree the new knobs look much nicer. You just know the money is being spent where it matters - pretty much like a Caterham 7 - everything is about performance and not much frippery. Just be aware there is no remote control, which might be important for you.
Or a KTM,deletes the two extra wheels......
Unless its a X-Bow of course ;)Quote:
Originally Posted by wee tee cee
Aye,That would do for your work......Quote:
Originally Posted by Alex_UK
I realised yesterday that I hadn't posted any photos of the amp now that it's mostly finished.
Here's the insides:
http://i2.photobucket.com/albums/y48...Finished01.jpg
Here's a closer look at the PCB:
http://i2.photobucket.com/albums/y48...Finished02.jpg
And here's a closeup of the Zobel network:
http://i2.photobucket.com/albums/y48...EL84_Zobel.jpg
My next jobs are to mount a dummy input selector switch and volume control pot and then re-attach the front panel and knobs. I intend to wire the dummy volume control so that it controls the brightness of the power LED. I have all the parts for this so I'm hoping to get that done later this week. The only other thing left to do is to block up all the input connector holes on the back that are now empty. I think I noticed some suitable plugs on eBay a while ago that should do the job. I'll post some more photos once I've got the whole thing finished off. :)
Have been playing the lap top/squeezebox directly through the valve power amp utilising the volume controls on both as the pre amp.Must admit,I think it sounds better without the pre amp.
Tried going back to my Naim 5i,didnt last long.
Maybe try a t amp as a half way house,saving some sheckels along the way.....
Quote:
Originally Posted by wee tee cee
anything is better than a Naim amp :sofa:
I'm glad you have cured your sibilance problems in all seriousness
Had a wee listen to the Naim again.....I think I might have to go down the valve route.I will wait till the bantum arrives and give it a good listen.We must be getting quite drunk because my wife told me the Naim is like a pair of loubitans-great to walk from a venue straight into a taxi,but you wouldnt want to walk about in them all day.....I sort of understood
either way I reckon its going to cost me in amps or shoes......
Both, I suspect! :lol:Quote:
Originally Posted by wee tee cee
I installed a matched quad of cryo treated E84L's tonight. First impressions are that they've improved the bass and the detail retrieval in the higher frequencies. The bass seems to drop lower and with more authority and I heard subtle details in one track that I'd never heard before. So I'm looking forward to doing hearing how they improve as they run in. I also have a pair of E80CF gold pins on the way that I found for a reasonable price on eBay. :eyebrows:
I also managed to find some grommets to fill the unused input socket holes in the chassis. So they've tidied up the rear panel nicely. Now I just need to sort out the power LED and front panel. Once I've done them I'll post some photo's. :)
I finally got round to finishing of this project today. I've fitted a new input selector switch which is purely to allow me to keep the knob for aesthetic reasons. I've also fitted a 4.7K pot where the volume control used to be and wired this in series with the existing LED resistor to allow me to fine tune the LED brightness. This has allowed me to tone down the brightness to a much more acceptable level. At 20mA it was enough to give you a migrain. :lol:
Unfortunately in my rush to get it connected back up again I forgot to take photos, so here's one of the amp in situ. I'll try to remember to more photos tomorrow as I plan to try adding some more tube damper rings then as an experiment:
http://i2.photobucket.com/albums/y48...KEL84_Done.jpg
I've got a cunning idea of a way to tame the transformer heat, so I'll be experimenting with that soon. :eyebrows:
Nice!
I quite fancy a tube preamp/headphone amp combo, but most (in my limited experience) are in the U.S (Shiit, Woo etc.).
Any UK versions about guys?
Edit: promoted question to a new thread