The Nine and The Nine Plus were Class A 50W or 55W... probably about 4A idle current per channel.
As to the "a lot"... well, I must admit that most of the "a lot" were either 70's amps, when good complementary devices were apparently harder to come by, or cheap amps, where push-pull with all NPN was cheaper. I guess there aren't that many modern high-end amps built this way, which makes me skeptical that there's a benefit to it... it's certainly no more difficult to build a push-pull solid state amp without minority carrier devices.
After thinking about this a bit more, it struck me that you could even, if you're so inclined, build a push-pull, Class A, high voltage amp using N-channel MOSFETs and a very similar topology to typical tube amps, with tube power and output transformers. Might be an interesting experiment....
Cheers,
Paul
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Just a comment from someone who has been interested in audio electronics for many years, on and off, but by no means at the level that the posters in this forum have, and prompted by Telstar's link above:
Is the so called 'valve sound' more because of the simplicity of a tube amp ( i.e. number of active components) rather than the actual usage of tubes rather than transistors?
Just thinking back to the 'valve sound' of designs such as the simple JLH Class A amp.
I'm not convinced that 'over complication' of tranny amps to produce low distortion designs might have some form of side effect that is not readily understood at this point in time.
After all I think most loudspeakers introduce something above 1% distortion in their own right so anything below this figures from an amp should be OK without resorting to 0.001% distortion figures.
Perhaps this has been covered elsewhere I suspect?
Cheers
Is the so called 'valve sound' more because of the simplicity of a tube amp ( i.e. number of active components) rather than the actual usage of tubes rather than transistors?
Just thinking back to the 'valve sound' of designs such as the simple JLH Class A amp.
I'm not convinced that 'over complication' of tranny amps to produce low distortion designs might have some form of side effect that is not readily understood at this point in time.
After all I think most loudspeakers introduce something above 1% distortion in their own right so anything below this figures from an amp should be OK without resorting to 0.001% distortion figures.
Perhaps this has been covered elsewhere I suspect?
Cheers
Strangely enough the exact same thought struck me whilst composing my message above.
I suppose someone must have tried this somewhere? Seems a logical experiment.
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Polsol - you have 'hit the nail on the head', from what I have read, it is indeed possible to reproduce tube circuits with Mosfets and people have done this. They don't sound like tube circuits necessarily.
Usually people prefer avoiding the use of an output transformer. A good exception to this is the Zeus amp by Susan Parker (google it) which is pure Class A with VERY few components. The trouble with output transformer is that it is expensive to make one with good audio performance.
Interesting question, is 0.001% distortion already too good - what is a good figure probably depends on the listener as some people like the warm sound of an amplifier with 2nd harmonic distortion and others don't. I think I read in a paper by Nelson Pass that about 1/3 of people like a little 2nd Harmonic, another 1/3 like a little 3rd Harmonic and the rest like a combination or as low distortion as possible.
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I just did some simulations of two bjt's set up as a simple 2-stage amplifier. With lots of feedback - low distortion. With local emitter degeneration and a little feedback I get higher distortion but nothing nasty. With very little emitter degeneration and more feedback to compensate I see lots of high order harmonics. All else being equal it appears in this simulation that emitter degeneration is less harmful than 'global' feedback.
In my simple world emitter degeneration can be thought of as other than local feedback. It can be thought of as input attenuation - the input signal across Vbe is reduced when the emitter is 'lifted off ground' (using ground as the signal reference) with a degeneration resistor and so the transistor simply 'sees' a lower input signal. Yes, I've gone mad - it's late and I'm going to sleep soon.
Usually people prefer avoiding the use of an output transformer. A good exception to this is the Zeus amp by Susan Parker (google it) which is pure Class A with VERY few components. The trouble with output transformer is that it is expensive to make one with good audio performance.
Interesting question, is 0.001% distortion already too good - what is a good figure probably depends on the listener as some people like the warm sound of an amplifier with 2nd harmonic distortion and others don't. I think I read in a paper by Nelson Pass that about 1/3 of people like a little 2nd Harmonic, another 1/3 like a little 3rd Harmonic and the rest like a combination or as low distortion as possible.
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I just did some simulations of two bjt's set up as a simple 2-stage amplifier. With lots of feedback - low distortion. With local emitter degeneration and a little feedback I get higher distortion but nothing nasty. With very little emitter degeneration and more feedback to compensate I see lots of high order harmonics. All else being equal it appears in this simulation that emitter degeneration is less harmful than 'global' feedback.
In my simple world emitter degeneration can be thought of as other than local feedback. It can be thought of as input attenuation - the input signal across Vbe is reduced when the emitter is 'lifted off ground' (using ground as the signal reference) with a degeneration resistor and so the transistor simply 'sees' a lower input signal. Yes, I've gone mad - it's late and I'm going to sleep soon.
Good loudspeaker drivers can have down to -60dB (0.1%) H2 with possibility
of H3 being even lower over a large part of their bandwidth.
Acoustic Elegance TD12M
http://493531664873718246-a-1802744...SBuUMyOAfX_uIaVCf8hiTqS8iw0ggf&attredirects=0
Their multi tone distortion can also be surprisingly good.
Also typically, they don't suffer increasing distortion with increasing
frequency to the same degree as most amplifiers.
T
The "Nine Plus" with such idle current - then I must have an ultimate amp after replace the operational amp ICs through AD797 or similar types. Interesting to know.
Regarded very similar topology to typical tube amps by using N-Channel MOSFETs and output transformers there are follow supplier:
Zero Feedback Transformer Audio Power Amplifier
and this thread:
http://www.diyaudio.com/forums/solid-state/24744-push-pull-using-only-n-channel-mosfets.html
This threads also of interest in this case (overview about topologies without solid state devices, that have reverse polarity):
http://www.diyaudio.com/forums/soli...e-ended-related-solid-state-output-stage.html
http://www.diyaudio.com/forums/soli...better-audio-non-complements-audio-power.html
Yes that is conjecture. It seems there was another post in between yours and the one you referred to, hence the confusion. I thought your post was a-typical for you,
but this explaines it.jd
I don't understand this. To understand this dialogue, my English isn't good enough. Especially the mentioned "another post" I don't find.
Perhaps regarded "one of the reasons tube amps sound better than SS amps" ???
I find only there:
Tube Pedals @ Ultimate-Guitar.Com Forum Archive
scroll to cutslikedrugsx, 10-15-2009, 09:52 PM
But I think this thread wasn't meant
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"one of the reasons tube amps sound better than SS amps" presupposes that tube amps sound better than ss. This is not a fact. YOU may prefer tube amps, I may prefer something else. But there is no established, accepted fact that tube amps as a rule sound better than ss.
jd
Right. But the subjective sonic impression of a great amount of music lovers with no circuit-related knowledge is, that tube amp sounds better. And I must admit, if I had no idea of electronics, I'd also think this. In real life (a normal day in a good hifi studio), this sonic difference is usually evaluated in favor of a tube amp.
The aim of my statements from post #601 and #608 was to mention the main reasons for this generally accepted observations.
One reason I have forget. The different clipping behaviour of tube and SS amps. Naturally a correct sonic demonstation presupposes at least 3 db (better 6 db) headroom to avoid the clipping aera (by soft clipping behaviour 12-15 db headroom). But in most cases nobody do keep them, that means, this is an additional reason to the above mentioned
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generaly, tubes amps owners or sellers use very good speakers
to listen/demonstrate those items...
compared with the same speakers, i doubt a tube amp will
sound anywhere as clean as a SS state one...
it will just reveal how innacurate the tube sound is ,
the thing being (literraly) enhanced with vast amounts
of second and third harmonics, not to mention the high
output impedance that completely reshape the bandwith and
balance of the original sound..
to listen/demonstrate those items...
compared with the same speakers, i doubt a tube amp will
sound anywhere as clean as a SS state one...
it will just reveal how innacurate the tube sound is ,
the thing being (literraly) enhanced with vast amounts
of second and third harmonics, not to mention the high
output impedance that completely reshape the bandwith and
balance of the original sound..
Well there is already a large body of knowledge on the differences in tube and ss amps in terms of freq response, distortion level and composition, output characteristics, clipping characteristics, supply rejection etc. These can readily explain sonic differences, and the rest, as you say, is personal preference. So it doesn't seem necessary to go down into the details of compementary devices or not to explain what is already explained.
Nevertheless, I think more ss amps are sold today than tube amps so does that mean ss sounds better? And if I prefer a tube amp, does that mean it sounds better? What's 'sounds better'? Technically tube amps, in general (but not always) are inferior to ss when it comes to faithfully reproduce the signal at their inputs, so how would that jive with 'sounds better'?
You see, there's a lot of ways to look at this, so the statement 'the reason why tube sounds better than ss' presupposes something that is not at all clear or certain.
jd
Not always. The typical tube amp surely fits your description.
I was as skeptical as you until I heard really good tube amps (i count just two of such).
So far, my SS attempts haven't been able to match that, when they should theoretically surpass it (no transformers, for one). The lovely Pass' F3 si both close and far to that goal.
I think I am the kind that likes the lowest possible distortion, so I find the above harder to explain. I think, though that triodes configured in PP, with SOTA output trasformers can achieve extremely low distortion, probably lower than 0.1%/1w that I clearly hear in my F3.
Actually I was thinking about an all FET amp with an output transformer. This would be the only true comparison point IRO tubes I feel - but then again, one doesn't tend to find output transformers on supermarket shelves anymore
IRO amp comparisons, I'd guess that if one did a blind test of different amps then this would be somewhat close to the ideal way of determining what one likes and dislikes. As you mention some like 2nd and some 3rd harmonics.
However, using the same speakers with different amps would be complicated by not ideal matched amp/speaker combinations.
Too many variables.
Thanks for pointing that out. However I guess this is the exception rather than the rule.
Also, can one distinguish between a 0.01% or a 0.001% distortion amp when driving into these speakers? A ratio of 10 to 1 maybe, 100 to 1, I would doubt it (given that different amp/speaker combos sound different to start).
nelson pass is in the good track about musicality.
the bad is that his design are powerhogs that have
poor specifications in matter of consumed energy/performances level..
so far, a mosfet amp correctly designed and biaised is out
of reach by tubes concurrents, whatever the level of price or
sophistication...
transformer coupled amps can t match directly coupled devices amps..
it will always distord the signal in matter of tonal balance.
to sound identical as a tube amp, a SS would need to be designed
not only with high bias, but also it would need a modification
of its frequency response with output impedance varying in function of
frequency...
that s not exactly high fidelity...
Sprechen sie Dutsch ? : AITOS - exquisit AUDIO
(ok, maybe poor spec'd in consumed cash/performance level)
(ok, maybe poor spec'd in consumed cash/performance level)
I know
Still it is hard to find (especially if we include HF reproduction in the requirements).
What looks great on paper often fails the test of the ears. This thread has been helpful to guess why.
I do agree.
I think a LOT of the sound "signature" relies in the output stage.