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Old 23rd April 2007, 01:53 AM   #21
AKSA is offline AKSA  Australia
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No comment.....
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Old 23rd April 2007, 01:59 AM   #22
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Hi Johan, nice to see you around again.


What really gets me listening is how even on the most complex music the amplifier keeps itself firmly planted in cohesiveness and those little details that often get lost with complex music with many transients and frequencies, in the most dense passages i can still hear those micro details and spacial cues that makes a well recorded live cd sound so good. Its not strident in the highs like most of the comercial SS I have hear in the past, but rather transparent without being spitty.I have been reading the Memory distortion articles and the Lavardin patents, looks like there are a load of inputstage ideas for me to toil with in the near future, thanks for the tip Hugh.

Colin
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Old 23rd April 2007, 02:00 AM   #23
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Glen, you've been warned about personal attacks. Take a two day break from this thread. Further action may follow.
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Old 23rd April 2007, 02:07 AM   #24
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Default If disillusionment comes with expertise.

I am happy being a novice. Glen, I am still waiting for yourself to offer me something useful and constructive rather than the attempted raining on my parade. Hugh,Carlos and a few others have offered me what looks like a few small bits of constructive help but are really far bigger than what they seem, its often those small things that make the biggest difference in life.


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Old 23rd April 2007, 06:29 AM   #25
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As a matter of policy I try and be positive and avoid pointing the finger but I do have an objection to Douglas Self's position. I've read most of what he's written over the best part of three decades and in one sense my concerns are that he is not scientific enough for me. (Now, for what its worth I'm in the JLH section of the forrest and have built some of his s.signal amps and own one of his 10watt class A.) But the problem for me, with Self's work, is that although he militantly claims to be an objectivist I feel he allows no scope for further discoveries and insights. I may be wrong but it always seems to be THD with him. This strikes me as unscientific. There seems to be no position for mystery in his work and anyone who doesn't subscribe to his understanding of orthodoxy is not worth taking seriously. I've recently read a broad sweep of Western science since the Rennaisance (I'm sorry I can't spell....no visual memory) and the thing that strikes you is the dead hand of orthodoxy that repeatedly resisted new insights....things that the powers that be said "just couldn't occur" and were later proved to be true. I'd like to think the aggressive objectivist would be gracious enough to leave the door open a little bit for new mechanisms other than THD.
I'm not sure who was the first to raise concerns about listening results verses "hard data" but in JLH's 1969 Class A article they are mentioned. What I like about his approach is that he did know his science and was rigoris in its application but was also opened minded enough to know that we hadn't grasped all that was in this field. If it sounded "good" or "bad" there must be a reason for it. I like hard science and "facts". and I understand myself well enough to know the emotional reasons in my personality that account for this prediliction!!!!! But having said that we ought to be open to having current orthodoxies turned on their head if needed.
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Old 23rd April 2007, 07:13 AM   #26
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It would be lovely if we can rather discusss the thermal issues brought up in that memory article/link.... It certainly gave this beginner a few new insights into the many factors that create a circuit... must hav read all those pages in 20 minutes and it was a pleasure...

Who'd haave thought that the heat retained in a sink would affect the DC operational point etc...
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Old 23rd April 2007, 02:49 PM   #27
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I noticed something while I was working on my amp over the last few months.

With the original compensation scheme, my amp sounded quite 'bright' - I liked the sound. However, if I put my ear next to the tweeter, I could hear a very faint hiss. I looked with a scope, and noted that the amp was oscillating at about 1MHz.

I tweaked the compensation (VAS Cdom from 22pF to 47pF) and removed the 10pF I had across the feedback resistor. All oscillation gone and no noise from the tweeter.

Clean square wave response.

The amp does sound different and I am willing to bet some people would prefer the original sound and others the 'new sound'. From the engineering perspective, the original compensation values were clearly not correct because the system was not stable.

So, I think compensation has a critical impact on the sound of an amplifier and just wonder how many great 'audiophile amps' have stability quirks (or not as the case may be) that that lead to a particular sound that reviewers happen to like . . .
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Old 23rd April 2007, 09:37 PM   #28
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Hi Colin,

(Your #22 - not to clog up the screen unnecessarily). Now I am raining on the parade - well, just a brief drizzle, then back to sun. I am delighted that you find your amplifier satisfactory. I recall my first taste of hi-fi; I was enthralled at what could come out of just one loudspeaker (then). But to get down to reality: I am not one to disturb exhilaration, after all, I am trying to cause exactly that, at least on the electronic side. But I get a mite alarmed at the effect an aura of mystery sometimes breathed into this by some like theatre smoke, might have on beginners. One reads about the "inhaling of the artist" becoming audible, or someone "feintly scratching on his guitar" (did the singer have astma or the guitarist catch his ring on something).

Such have nothing to do with hi-fi - it was there all the time; what I am trying to say is, micro details and spatial cues should be there all the time. Not detracting from your achievement (and that without a scope? - good of you), but there is nothing mysterious about a blameless amplifier. Audio frequency is after all a very small fraction of the frequency band used at present, down by almost dc (our cell-phones glibly work at >1 GHz). Any decent design should be blameless, and even beginners are capable of understanding this, given the right info. There are not too many things here to be still discovered, at least as far as amplifiers are concerned. I expressed my concern about the utterence of matters "that are not yet fully understood" before. There has been such a wealth of research regarding hearing, mainly in order to correct hearing deficiency, that what an amplifier is supposed to do, at least, will yield as many surprises as grade 3 arithmetic. Scientists do not know everything, but we do know that 3 + 5 =8, etc. - not much scope for research there.

That to encourage you, and also referring to my post #19 at the end, mentioning why it is really necessary to be able to look at amplifier response in order to get compensation safe. I sincerely hope you can afford a scope soon; a signal generator you can build yourself. It will be very rewarding not only to get it right, but to see why you got it right! Thanks for sharing this with us.
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Old 23rd April 2007, 10:01 PM   #29
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Quote:
Originally posted by Jonathan Bright
....things that the powers that be said "just couldn't occur" and were later proved to be true. I'd like to think the aggressive objectivist would be gracious enough to leave the door open a little bit for new mechanisms other than THD.
....and there I did just that (your first sentence) in my previous post!

But you would have realised that since 1969 matters did improve - particularly the discovery of the effect of high order harmonic distortion, TIM and loudspeaker-amplifier interface distortion. This was not so much discovering new things about hearing, as faults in amplifiers that we did not have/cared about before. Regarding Self I mostly recall his fight with subjectivists and their pseudo-scientific stance. But I agree that a blinkered stance is dangerous, and I would be surprised if he ignored high order h. distortion. Wake-up call for myself then!

Bonsai,
Exactly what some of us meant! Some may not have been bothered by the slight hiss, and carried on with an amplifier having goodness knows what spurious effects in the audio band. (What you found might even have had a larger amplitude; I often found that a scope probe - even X10 - reduced or cancelled an h.f. oscillation.)

If you care to reply, did you measure with the loudspeakers connected or not?
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Old 23rd April 2007, 10:10 PM   #30
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Quote:
Originally posted by Jonathan Bright
But the problem for me, with Self's work, is that although he militantly claims to be an objectivist I feel he allows no scope for further discoveries and insights.
Jonathan (great name, that!),

I don't see Self as an objectivist, but more as an anti-subjectivist. Without knowing the man, I would assume that if he heard something that didn't sound good, but measured well the he'd chase this down with as much vigour as he lambasts things that don't change measurements or, to him, the sound.

I don't see that because someone uses the tools of one side, and points fun at the other, that he necessarily joins a side. A personal example is that, although I am not a terrorist, I do not agree with the policies of GWB. there is always at least a third 'side'.

But, that's my opinion, and I'm welcome to it... !
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