View Full Version : preamps
Dave Hewitt
14-11-2010, 20:25
Hi'
Just like to thank Ian Walker for putting up with us for an afternoon and,also supplying the scram.Heard Ians s&b transformer preamp,Marcos croft and Nick's self built job.Very impressed with all 3 each having a different portrayal of the music but had to give Nick's the thumbs up.I also took my kondo m77 clone and I will be sending a letter to Messrs Kondo to come up with somethig better,or perhaps I copied it incorrectly
Dave.
Ali Tait
14-11-2010, 20:34
Yes Nick's pre is quite something,easily the best I've heard anywhere.
Hi Dave,
Nice meeting you again today, mate, and of course Avinash and Nick! :)
Unfortunately, your 'Kondo' did sound a bit out of sorts, but it was in fairly illustrious company.
Yes, Nick's preamp is phenomenal, and like Ali, I'd say it's easily the best preamp I've ever heard.... The sheer musical realism and PRAT of the 'all balanced' circuit is quite something! :eek:
However, Ian's new transformer based preamp (sorry, don't know much more about the technical details than that) was also superb, but in a different way. It's similarly easily the best passive preamp I've heard to date - and you can really hear what the absence of mains does to the noisefloor, and hence musical expression and communication...
It totally outclassed his World Designs preamp, IMO, and will now no doubt be forming an integral part of Ian's system with his new copper amp - superb stuff!!
The Croft was pretty good, musically, (not as good as Nick's preamp, though, or Ian's new one in some ways), but was at a slight disadvantage due to the partnering power amps used not being sensitive enough to cope with the reduced gain produced by the Croft's shunted stepped attenuator (it seemed to 'run out of puff'), and so the Croft gave a somewhat lacklustre performance with the power amps we used today (an Almarro and two of Dave's DIY valve designs), in comparison to what I'm used to with my copper amp at home (which is significantly more sensitive) - in fact, it was well short of that sonic standard.
In my experience, obtaining the optimal gain structure for a pre/power amp is essential in order to ensure that the dynamic range is correct, and with it the clarity and 'life' that is neccessary to make music sound real.
It's rather like achieving the correct recording level on either digital or analogue recording equipment when making recordings of music - get it too low, and the resulting sound is rather soft and lacking in punch (which is kind of how the Croft sounded yesterday), get it too high, and the sound saturates and becomes unpleasant, but get it *just* right and everything clicks into place.
I'd like to hear Nick's preamp again and compare it to the Croft, which we've planned to do around Christmas, when I have my copper amp back from being repaired. I'm picking that up tomorrow. I suspect that this will level the playing field significantly, as the copper amp matches the Croft perfectly and provides the optimal gain structure, but I'm not sure that even then the Croft will overall reach the same sonic standard of Nick's new preamp, as it is very special indeed!
Anyway, it was a very interesting sesh, and fun as usual when we all get together like this :cool:
Marco.
Ali Tait
14-11-2010, 23:03
What's up with the amp Marco?
Hi Ali,
One of the GEC KT88s went dead short and took out the mains transformer with it!
The long and the short of it is that a new bespoke hand-wound mains transformer (bigger and of higher capacity) from Sowter has now been fitted, enabling Anthony to get another 10 WPC from the amp (so now 40W of Class A), and I'll also be installing a brand new (unused apart from testing) matched quad of GEC KT88s, so it should sound a bit different :)
Marco.
Ali Tait
15-11-2010, 06:45
Every cloud has a silver lining!
Lol - indeed!
I should've changed the output valves sooner... Well they were originally fitted in 1998 (well before I bought the amp)!! :eyebrows:
Those GECs would've had thousands of hours on them, but the thing is everytime I took them to Anthony's to be measured on his valve tester, they tested perfectly with nearly full output on all the relevant parameters, so I left them in because I liked how they sounded.
As you know though, despite that, valves can go at anytime due to many factors.
Anyway, it'll be very interesting hearing how the amp sounds now!
Returning to preamps, when I compare the Croft again to Nick's preamp (using the copper amp this time as a reference), it'll determine if it stays in my system, or if I'll be getting Nick to build me one of his ;)
Marco.
Ali Tait
15-11-2010, 07:47
That's the good thing about good NOS valves,they tend to last much longer than the modern equivalents. Might be more expensive initially,but probably save you money in the long run. Sound better too!
Indeed - there's no way on this earth that any current production KT88s would've lasted anything like that long.
As for sound quality, GECs are very special indeed. It'll be interesting now I've actually got a new pair to use! ;)
Marco.
StanleyB
15-11-2010, 08:08
The Croft was pretty good, musically, (not as good as Nick's preamp, though, or Ian's new one in some ways), but was at a slight disadvantage due to the partnering power amps used not being sensitive enough to cope with the reduced gain produced by the Croft's shunted stepped attenuator (it seemed to 'run out of puff'), and so the Croft gave a somewhat lacklustre performance with the power amps we used today (an Almarro and two of Dave's DIY valve designs), in comparison to what I'm used to with my copper amp at home (which is significantly more sensitive) - in fact, it was well short of that sonic standard.
Finally someone else who noticed the same issue I have with the Croft design.
I used to borrow a number of Croft preamps and amps in order to test my DAC designs. But I couldn't quite understand why the dynamic range of my setup was so lousy. Only after I dug out my old reference amp from my loft did I realize that it was the Croft that was compressing the reproduction.
Hi Stan,
I can't speak of whatever Croft preamps you had, but with mine it's only an issue if a power amp is used that isn't sensitive enough (i.e. the gain structure isn't right).
My Croft preamp sounds superb with the copper amp (as this is what it has been matched with), which is much more sensitive than any of the power amps it was partnered with yesterday :)
Also, like I said, my Croft uses a shunted stepped attenuator, which reduces gain by 6db, so when partnered with a fairly insensitive power amp, it's a recipe for, shall we say, not the best results!! ;)
Marco.
StanleyB
15-11-2010, 08:24
Hi Marco, they were a number of preamps and amps, borrowed from a Croft dealer. All of them produced the same reduced dynamics effect, which I didn't quite manage to get to grips with. There has to be a common denominator for it. You suggested the shunt pot, but why do you think that is the source of the problem?
EDIT: just saw your comment on the 6dB loss. I have my own opinion about the use of a high value resistor before the volume control to get the shunt circuit to work, and my alternative solution. But I'll keep that to myself before someone uses it in their design...
Hi Stan,
The shunted pot was only the source of the gain problem I experienced yesterday when the Croft was partnered with less sensitive power amps than the copper amp, which it has been matched with.
The other sonic issues you're referring to would probably explain why I've had my own Croft preamp extensively modified! It is FAR from standard ;)
Marco.
Ian Walker
15-11-2010, 08:28
Hi'
Just like to thank Ian Walker for putting up with us for an afternoon and,also supplying the scram.Heard Ians s&b transformer preamp,Marcos croft and Nick's self built job.Very impressed with all 3 each having a different portrayal of the music but had to give Nick's the thumbs up.I also took my kondo m77 clone and I will be sending a letter to Messrs Kondo to come up with somethig better,or perhaps I copied it incorrectly
Dave.
No need for thanks Dave it was great to see you all again...even though you ate me out of house and home hehe indeed i was filled with dread when Di put the biccie tin on the table and i saw Dave n Avinashes faces light up...lesson DO NOT get bicuits out when these two are around!!Jokin aside it was a really enjoyable afternoon,Nicks pre being the highlight we all agreed..nice one Nick,with My new pre and Marco's Croft not toooo disgraced. Mmm Nicks pre how do i get one...what can i find to flog:scratch:...oh aye who robbed me Korn cd?
Yep, thanks for the fun interesting day Ian, I bet that Marco made off with your CD.
Hahaha... Yesh, I've jusht had a wee peek-ette at my sofa and noticed that it's sitting there on top of the CDs I brought round... Sowee :eyebrows:
Anyway, I'd better get my ass in gear and head off to South Wales!
Byeeeeeeeeeeeeeeeeeeeeee :wave:
Marco.
anthonyTD
15-11-2010, 10:37
hi all,
well it would seem a good day was had by all then.:)
good news on the preamp Nick,hopefully i will get to hear it one day.
regards,anthony,TD...
Yep, twas fun. Only problem is the pre will go to its owner in a months time, so I will have to rob the bank and build myself one :-). Having done that (as I said to Marco) the next obvious thing to do is build a power amp (possibly push pull 300b) that takes the balanced output to drive the output stage with no extra phase splitter or non balanced stage. All good fun.
anthonyTD
15-11-2010, 11:21
Yep, twas fun. Only problem is the pre will go to its owner in a months time, so I will have to rob the bank and build myself one :-). Having done that (as I said to Marco) the next obvious thing to do is build a power amp (possibly push pull 300b) that takes the balanced output to drive the output stage with no extra phase splitter or non balanced stage. All good fun.
hi Nick,
sounds good!
Anthony,TD...
Ali Tait
15-11-2010, 12:30
Shock Horror!! Nick Gorham builds PP amp!
What, you mean other than the one I am building for you? :-)
Ali Tait
15-11-2010, 13:34
Yebbut that doesn't count coz it's direct coupled! Anyway it's not built yet :-).
themystical
15-11-2010, 20:05
No need for thanks Dave it was great to see you all again...even though you ate me out of house and home hehe indeed i was filled with dread when Di put the biccie tin on the table and i saw Dave n Avinashes faces light up...lesson DO NOT get bicuits out when these two are around!!Jokin aside it was a really enjoyable afternoon,Nicks pre being the highlight we all agreed..nice one Nick,with My new pre and Marco's Croft not toooo disgraced. Mmm Nicks pre how do i get one...what can i find to flog:scratch:...oh aye who robbed me Korn cd?
Not sure about your speakers or the preamps Ian but the biccies were the best yet!:lol:
Dave Hewitt
15-11-2010, 20:20
Greedy bugger.
Dave.
Yesh, those were Ian's most favouritist chocolate mint creams... I could see the horrified look on his face as you two were guzzling them up! :lol:
Btw, I've now got the copper amp back from having 'surgery', and it sounds better than ever - in fact, bloody amazing! :eek:
There's also no problem whatsoever either with gain on the Croft when used with a suitably sensitive power amp, which begs the question, how do equipment designers set the sensitivity of their amp designs without knowing what kit it's going to be used with?
Unless there is some fairly accurate 'known standard' for setting sensitivity, this for me is a potential recipe for sonic disaster, as indeed was shown to an extent by what I heard on Sunday.
My view is that anyone designing a DIY power amp should have the partnering preamp in situ to use as a reference (or vice versa), in order that the correct gain structure can be obtained, as this is absolutely crucial in terms of achieving optimum sonic performance.
Perhaps Nick, Anthony, Dave or anyone else who builds their own amps would comment? :)
Marco.
My view is that anyone designing a DIY power amp should have the partnering preamp in situ to use as a reference (or vice versa), in order that the correct gain structure can be obtained, as this is absolutely crucial in terms of achieving optimum sonic performance.
Even having that doesn't in itself help as much as you may think as it then depends on what speakers are after the amp and what source is feeding the preamp
That's very true, Nick.
I just wondered in general how you tackled these sorts of variables during the design process, that's all, and in particular how the optimal amplifier input voltage sensitivity is achieved in the absence of knowing what you've just mentioned :)
Marco.
In the case of the pre you heard its a guess. The output TX has the option to provide different gain depending on the way the secondaries are wired.
As you heard it, it gives unity gain with the attenuator at about 2 o'clock. So I would guess your setup is running the preamp at about a -10dB level (or less) from what you were saying about the pot position.
Yep, whilst trying both to obtain/ 'chase' the correct dynamic range/impact I'm used to hearing from the Croft (in conjunction with the copper amp in my system) and also a reasonable listening level in Ian's system (whilst using either the Almarro or any of Dave's power amps), the pot on the Croft needed to be turned up to the 2 o'clock position (remember this was with a digital signal), which if I'd done that at home would've blown the windows out (on vinyl or CD)!! :eyebrows:
The trouble then was that in trying to achieve the above, the power amps used were on the verge of clipping and the sound distorting, hence the importance of having the correct gain structure in place which, as you say, suits the whole system and not just one component, enabling a strong enough signal for the power amp to amplify without overuse of the volume control on the preamp.
It's definitely a fine balancing act to get absolutely right!
As you know, I loved your new preamp, but if it were used in its current state (with such massive gain) with my copper amp and 95db efficient Tannoys, the volume pot would likely never see past the 8 o'clock position! :lol:
Of course I know things could be adjusted accordingly, but I must admit that until I'd heard what I did on Sunday, I didn't realise just how crucially important this sort of stuff is.......
Marco.
In general the gain of a system ought to be such that for normal listening levels (not quiet, yet not widow rattling) the volume control is around the 12 'o clock position, say between 11 and 1 'o clock.
That way there should be plenty of 'headroom' for transients and loud passages, yet the potentiometer is operating in a position where the two channels are well matched. (Those of you who use a Quad 33 control unit will know that the balance is lop-sided until the volume is turned up to '4'.)
I am however guilty of not practicing what I preach: with my Levinson 28 preamp, when playing a CD or using the tuner the volume is around the 10 'o clock position. This can be adjusted by altering the gain of the pre, however to do this entails opening up the unit and setting the DIP switches to a lower gain. As this entails removing 8 socket headed screws, lazyness has got the better of me - it all just sounds so good as it is, I'm inclined to leave it alone.
Depending on which cartridge I'm using and whether or not I use a pre-pre amp the volume can be anywhere between 10 and 2 'o clock.
Regards
Agreed, Barry.
Normal listening levels for me when relaxing with music (when the lads aren't round for a sesh ;)) is around the 9-10 o'clock position on the Croft, which is just nice. When the crew are over, however, and we're having a sesh, it's most likely to hover around the 12 o'clock position, or up to 2 or 3 o'clock when playing Rammstein, Tool, Wolfmother or such like :fingers:
But in my system with the copper amp, when the Croft is used at the 2 o'clock position, with vinyl or CD, the sound is absolutely deafening (I mean when it starts to pressurise the room and the cheeks on your face enter G-force mode :eyebrows:!), and yet on Sunday when used in that position with the low sensitivity power amps on the day, it was like the sound I get at home when the Croft is at 10 o'clock, so as you will appreciate, that's a pretty big discrepancy..........
I'm not sure roughly how many db four knob positions on a preamp equates to, necessary to achieve a similar volume level.
However, input sensitivity aside, I guess one has to remember that it was a 20W integrated SET amp that was mostly being used as a test power amp, and later a small EL34 P/P amp, neither of which have anything like the sheer grunt of the copper amp (even if they were similarly as musical sounding), although Ian's Tannoy Canterburys are to my knowledge similarly as efficient as my Lockwoods.
It's all very interesting (and for me) highly educational!
Marco.
anthonyTD
16-11-2010, 17:10
hi all,
marco's copper amp needs around 600mv for full output and its input impedance is [from memory] 470k so a big diffrence from most modern power amps which can be in the order of 10 to 50k impedance and around 1 to 2v for full output!
which is i supect the reason marco's modified croft didnt do quite what it does when connected to his amp. the copper amps are very dynamic even at low volumes so can be driven quite easily.
my own prefrence is to have what ever volume control used driven between two active stages that will drive current,eg; the soul-mate preamp that i designed in 2004 which i still use in my own system.
however, i understand that there are horses for courses and diffrent ways to skin a cat [excuse my expression] and we all have our diffrent opinions, etc, i have no doubt that nick's preamp was/is undoubtably a bit special, so it will be intersting to have a listen when he gets round to building another.:)
Anthony,TD...
Hi mate,
Thanks for that - very interesting..... It certainly explains what I'm hearing :)
marco's copper amp needs around 600mv for full output and its input impedance is [from memory] 470k so a big diffrence from most modern power amps which can be in the order of 10 to 50k impedance and around 1 to 2v for full output!
Although I can't see what sonic advantages the modern approach above would have :scratch:
I suppose it's yet another example of audio design today going more backwards than forwards! :doh:
Marco.
Reid Malenfant
16-11-2010, 21:54
Although I can't see what sonic advantage the modern approach above would have :scratch:
I suppose it's yet another example of audio design today going more backwards than forwards! :doh:
Marco.
A lower input impedance will generally result in a lower noise floor from said equipment. All resistors are ultimately subject to Johnson noise (google it) & a lower value resistor resulting in a lower input impedance should lower the noise floor. 470K is pretty high & will generate quite a bit more noise than a resistor of 47K ;)
A good bit depends on implementation however. Amplifiers that use series feedback will definately benefit from lower impedances. Amplifiers that use shunt feedback (inverting amplifiers) can often get away with a higher input impedance as it works in a slightly different way. Rather than sound hissy, shunt feedback is more of a gentle russle with less high frequencies prevalent in the noise floor.
600mV is (as far as i know) less sensitive than certain Quad equipment but vastly more sensitive than say Krell power amps which seem to have a pretty constant gain of 26DB. This can be handy as all there power amps require the same voltage drive to generate the same power.
I agree that it can be a pita to match stuff. Just make sure you have a pre amp that can supply a decent amount of current so it can drive anything & the position of the volume knob really doesn't matter :eyebrows:
Admittedly it can be annoying feeding a sensitive power amp from certain pre amps as a small increase with the volume control can cause a major increase in volume :doh:
Hi Mark,
Thanks for that, but of course not being a techy person, much of it goes right over my head......
A lower input impedance will generally result in a lower noise floor from said equipment. All resistors are ultimately subject to Johnson noise (google it) & a lower value resistor resulting in a lower input impedance should lower the noise floor. 470K is pretty high & will generate quite a bit more noise than a resistor of 47K ;)
...however, what I would say it that the copper amp has an extremely low noise floor (and sounds stunning), so as usual, there must be something more to it than that! :)
I'm sure Mr Matthews will be along later to comment :cool:
Marco.
Reid Malenfant
16-11-2010, 22:17
I was going to add that you can keep the same gain from the power amp even if you lower the input impedance by reducing the resistance of the feedback network (assuming the amp isn't open loop & uses no overall feedback).
It'd result in lower noise & a lower DC offset voltage :) You'd need a pre amp that could drive it though or bootstrapping the input could raise AC input impedance.
I'll be 100% honest though, i know naff all about valve power amps :eyebrows: I guess that in certain respects they should be similar but in reality i have no idea :cool:
hornucopia
16-11-2010, 22:26
Playing Hafler DH101/CD -F3, into 98db speakers, loudly, position 11 as I type.
I used to have big problem using DNM pre/Power into both Klipschorn (the big one) and later, Avantgarde Duos. Could hardly get above 'On' before it was too loud for conversation in a room. Had to use 20dB attenuators.
Nick's Pre-amp sounds intriguing!! Maybe I could put together an AOS system? I already have a Hewitt,(F3) in fact 2 counting the Lightspeed I normally use (Hafler just for m/coil input.)But I'm keeping my speakers!
Great to own something hand crafted, made by someone who cares. Spent my working life making food for others, that I cared about. Just keeping the concept going here!
Dave Hewitt
16-11-2010, 22:34
Hi, Could Mr Walker come to the front and tell us how he's getting on with his tvc now he has had a chance to get used to it?
I only had 1 biscuit,Dave.
Thermionic
17-11-2010, 00:03
Respects to all here, and not wishing to state the obvious to the engineers present.
But when I was a boy there was something called ‘line level’ and this was generally considered to be 0.775 of a Volt into an input impedance of 600 Ohms. This was ‘Zero Level’ on a proper VU meter, and was a professional audio and telecommunications standard. The termination impedance of 600 Ohms was low enough not to cause HF loss on moderate lengths of wire, and it was usual to have a ‘balanced line’ of send, return (+ and -) and earth with 600 Ohm transformers at each end of the line. For domestic use an un-balanced connection with an input impedance of around 20K to 100K Ohm was used because it was probably easier and cheaper to implement.
Things were simple and pre-amps were expected to give around a Volt into a power amplifier, and the power amp would expect to achieve full undistorted output with an input of around 0.775 V. There were though notable exceptions as my Quad IIs need about 2 volts, though it was not unusual to have a pot on stand alone power amps as well (Crown / Amcron).
CD came along and I believe a sort of ‘horsepower race’ started with line output levels increased by some, probably to make their products sound louder in the dem. room and 2 Volts seems to have become a new ‘standard’.
Actually I would be surprised if there isn’t a current European standard, who remembers the DIN Hi-Fi one?
Point is, the Hi-Fi world seems to have ‘forgotten’ what line level should be.:doh:
Just a non-engineer’s point of view.:)
Yep, there is still 0dBv as you say, but CD broke that to some extent. And I dont think 600R has actually been used for years, and then it was really only telephone based.
anthonyTD
17-11-2010, 10:09
Hi all,
just to clear up a few things, the amp that Marco uses has multiple feedback paths, over-all feedback i.e.; from secondary of output transformer to first gain stage [standard practice] but also individual feedback around separate chosen stages, this allows one to concentrate different amounts of feedback to the parts of the circuit that need it most instead of just increasing the over-all feedback to a degree where the designer hopes it will take care of all problem areas in one go. The latter is a recipe for disaster in my opinion as it can turn an otherwise potentially very good sounding amp into a dull, lifeless but perfect square wave producing pile of tat!
this design philosophy is not only relevant to valve amps but also solid state, there are some very good sounding/performing designs from both camps, designers who actually care about how to solve individual problems at source instead of using sticking plasters will always win as far as producing equipment that really works and connects with the soul.
Anthony, TD...
Cheers, Anthony. I'm sure that Mark, Nick and others will understand and appreciate the explanation.
this allows one to concentrate different amounts of feedback to the parts of the circuit that need it most instead of just increasing the over-all feedback to a degree where the designer hopes it will take care of all problem areas in one go. The latter is a recipe for disaster in my opinion as it can turn an otherwise potentially very good sounding amp into a dull, lifeless but perfect square wave producing pile of tat!
Hear, hear - feck the measurements 'obsessives', for they'd know not a good sound if it jumped up and bit them on the arse! ;)
The copper amp (especially since its recent 'surgery') is one amazing sounding amplifier, and I've a very happy bunny! :cool:
Btw, I'm sure you'll be very impressed with Ian's new transformer-based passive preamp that Nick has made. It's a corker!
Marco.
Reid Malenfant
17-11-2010, 12:04
Sounds like an NDFL (nesting differential feedback loop) or are you talking about standard local feedback to linearise a stage :scratch:
If NDFL then yes i have used the very same to good effect in solid state power amps as well as local feedback. I'm not one for using huge amounts of overall negative feedback either, 10 or 20Db maximum (depending on amplifier implementation) generally results in a decent sounding amp rather than your description of a pile of tat Anthony :lol:
Hi all,
just to clear up a few things, the amp that Marco uses has multiple feedback paths, over-all feedback i.e.; from secondary of output transformer to first gain stage [standard practice] but also individual feedback around separate chosen stages, this allows one to concentrate different amounts of feedback to the parts of the circuit that need it most instead of just increasing the over-all feedback to a degree where the designer hopes it will take care of all problem areas in one go. The latter is a recipe for disaster in my opinion as it can turn an otherwise potentially very good sounding amp into a dull, lifeless but perfect square wave producing pile of tat!
this design philosophy is not only relevant to valve amps but also solid state, there are some very good sounding/performing designs from both camps, designers who actually care about how to solve individual problems at source instead of using sticking plasters will always win as far as producing equipment that really works and connects with the soul.
Anthony, TD...
That's how my old Crown D-60's are done (local feedback). For the pro side, there's also VI limiting on each stage (that should cause Mr Dunn heart failure :LOL:) which prevents a blown trannie further back in the amp taking the rest out with it if it fails. Only needed once on one of mine ten years ago when a driver went down.
Ian Walker
17-11-2010, 17:29
Hi, Could Mr Walker come to the front and tell us how he's getting on with his tvc now he has had a chance to get used to it?
I only had 1 biscuit,Dave.
Mmm must have struck a chord with you has it Dave?.
I'm not really jumping to conclusions with it until i try it with my new amp when built. I must say though up to now i like it very much although it does take some getting used to..the reason being is at first you think there is something missing as its totally quiet,i mean absolutely deathly quiet..so what you perceive to be music missing is actually noise..i proved this to myself by plugging the active pre back in and there it was...a sort of background hue to everything The new pre is i think a big improvement over the WD being far more detailed,quiet and hear through than that,and although its a passive it has plenty of drive being transformer coupled and enough valviness to the sound due to the buffer going through it..so yes very pleased indeed thanks Dave:)
anthonyTD
18-11-2010, 09:35
Sounds like an NDFL (nesting differential feedback loop) or are you talking about standard local feedback to linearise a stage :scratch:
If NDFL then yes i have used the very same to good effect in solid state power amps as well as local feedback. I'm not one for using huge amounts of overall negative feedback either, 10 or 20Db maximum (depending on amplifier implementation) generally results in a decent sounding amp rather than your description of a pile of tat Anthony :lol:
hi mark,
i use about 12 to 14DB of total feedback in the copper amps,this is shared between over-all feedback and localised feedback around certain stages that i feel need a bit extra!
my description of a pile of tat:doh: was aimed at amplifiers that have been designed to test well but actually sound awful, what i was trying to emphasise is that it is possible to design a piece of audio kit to not only test well but also sound good when special attention is paid to certain key areas within a particular design.:)
Anthony,TD...
my description of a pile of tat was aimed at amplifiers that have been designed to test well but actually sound awful, what i was trying to emphasise is that it is possible to design a piece of audio kit to not only test well but also sound good when special attention is paid to certain key areas within a particular design.
Indeed - and it is this that separates the real electronic engineers/equipment designers from the measurement-obsessed pretenders in white lab coats, born with an oscilloscope stuck up their arse! ;)
Marco.
Reid Malenfant
18-11-2010, 15:59
hi mark,
i use about 12 to 14DB of total feedback in the copper amps,this is shared between over-all feedback and localised feedback around certain stages that i feel need a bit extra!
Well if they are class A they'll inherently be more linear anyway than a class B jobby. That's still pretty low though ;)
Cheers for the info :)
Indeed - and it is this that separates the real electronic engineers/equipment designers from the measurement-obsessed pretenders in white lab coats, born with an oscilloscope stuck up their arse! ;)
Marco.
Actually, were there many of these in the UK?
Certainly, in the 70's, many far eastern designs were almost deliberately crippled because of the need to get the THD figures as low as possible - market led and with ignorance of the different kinds of distortions out there that really do make a difference to the sonics. Whatever "we" think of them, in the UK it was the likes of Linn and Naim in the mid to late 70's that got us listening again, like the audio-inclined parents and grandparents of my generation used to do before audio took off in the early 70's. Just my views though ;)
anthonyTD
18-11-2010, 19:43
Well if they are class A they'll inherently be more linear anyway than a class B jobby. That's still pretty low though ;)
Cheers for the info :)
:)
hornucopia
18-11-2010, 20:06
As the current owner of a Lightspeed, made by Dave, sold to me by Ian, I'm getting worried that I'm getting left behind!(Not really!)
I tried it against an 'Eva' earlier this year. Thought the Eva lost all the magic I'd found in the Lightspeed.
Was only later I thought that, the Eva having a wooden case, it might have been affected by being stuck above twin toroids in the F3!
But my (uprated) Hafler Pre sounds pretty fine when I use it for LP/CD.
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