Sound Quality Vs. Measurements

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Seriously non-linear feedback systems can exhibit chaotic behaviour. That may be what happened with your diesel engine. It is also surprisingly easy to create apparently simple mechanical systems which are chaotic, such as some compound pendulums.

The Pass paper you link to is notorious for denying that emitter/source/cathode degeneration is feedback (R4 in fig 9). Not to start that argument again here, but be aware that Nelson Pass is not mainstream however much his fans wish he were.


If this was the old days I would go to Garon records and say if you see Michale Gerzon ask him to pop in to see me ( one never visited him at home , he never answered the door ) . Alas I can not do that now . Describing a feedback amplifier is quite useful as a filter . I would elaborate about a problem I solved when using global feedback to illustrate the complexity of it . I wont , instead I will let Michael do it for me . Michael was in life very complex and shy . In print he was what I will never be , A master of English . Michael I suspect would outrank anyone here as a mathematician . If not the people who said so at Oxford were fools and the tax payer should be told .

http://www.audiosignal.co.uk/Resources/Why_do_equalisers_sound_different_A4.pdf

Nelson Pass is doing what I do . He gives a picture . I notice he ducked controversial subjects in my link . Douglas Self is excellent especailly when describing two pole compensation . He shows why it should be distrusted and then it works . It works very well yet seldom is discussed . Very well , but not quite magic . I would imagine Scott would be one to ask ?

Self sometimes denies the emitter as feedback if a VAS . He got angry with me for using it . I wrote back and said " No it is to lift the base to help the current mirror " . Alas he had by then assumed I had thought of it as feedback " . I neither did , nor didn't . I did point out his current mirrors don't work properly , build them and you will see . If that VAS resistor is replaced by a diode things are not the same even if the DC conditions are the same ( easy ) . Makes me think Pass is right to have categories . I never fit diodes to cathodes for this reason . I do when getting going . Resistors are marginally cheaper . I don't fit transistor CCS to valves because my friends don't like it . I want to as they must be the very best . Using a LM337 as one is going too far .

BTW . Having Michael visit me at work was risking my job . My ex boss didn't like him . I recently phoned him about Michael . He was genuinely sorry and said he wished he had been nicer to him . In fact the two of them were very similar even down to their hidden origins ( Check , Jewish , my boss more the one who was hiding . Maxwell was another ) .
 
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BTW . The diesel engine I described was an example of optimism . Very large diesel engines are almost as restricted as gas turbines except the revs are very different . For example the engine of a type 47 locomotive has from memory a rev range of about 100 RPM optimum ( circa 950 to 1100 ) . So what is that whistling sound as it leaves the station ? That is the turbo . The engineers kept increasing the turbo pressure . The chaotic failure was caused by that . The mechanism is not known , the cure is .

Electric generators and motors optimize the use of the power , the restricted rev range is not a problem .

I just noticed the PPI phone calls I get ( unwanted calls about insurance I never had ) are very distorted . It is like it is analogue . It must be digital ? Wonder why it has degraded ? It's the only exercise I get so don't care too much . Some friends get very heated about it . I can phone someone and get it stopped . I can not be bothered .
 
Distortion spectra, which starts out low , in the miliwatt range and then go high as power increases seems to fair better than those which starts out high then lowers as power is increased, in subjective listening test ..


I had touched on this many moons back any additional thoughts ... ?

No additional thoughts. In the Mother Nature sounds reflected, or transferred, by any media, are more distorted the louder they are. And this distortions are heard as cues to the media, not as distortions. Like, you hear the wood, the stone, you hear sounds on the lake, in the bathroom, and so on. They are not heard as distortions. That's why distortions of electronic media if they follow similar pattern are not recognized as distortions.
 
In the Mother Nature sounds reflected, or transferred, by any media, are more distorted the louder they are. And this distortions are heard as cues to the media, not as distortions. Like, you hear the wood, the stone, you hear sounds on the lake, in the bathroom, and so on. They are not heard as distortions. That's why distortions of electronic media if they follow similar pattern are not recognized as distortions.
:up::up::up: ...

Frank
 
Wavebourn, what do you think about this......
 

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Wavebourn, what do you think about this......

I don't know, I don't have such experience. I even designed a "harmonizer" with a knob to add tube distortions, but nobody likes it. It is definitely a myth created by people who believed in THD numbers of Japanese amps, in order to explain why some people did not like them. It is very simple, to believe that others are wrong, instead of questioning own beliefs.
 
Maybe you used the wrong active elements, and/or marketed it to the wrong people? Isn't the Aphex Aural Exciter all solid-state?

I used exactly what the "Tube Sound" myth is about: a vacuum tube. :D

The result is, when "tube sound" control is available nobody likes it. But this fact can't disprove the myth: people who want to believe in the myth claim that "the wrong tube is used", or "used wrongly", and so on, despite the device adds what they believe tube amps add: low order distortions.
 
Wave, sit back and try to remember in the next say 5 minutes, all of the myth, magic and voodoo going on in audio in general. Then tell me - why are you surprised?

This hobby seems to be a magnet for spin doctors, voodoo witches and spinners, in all honesty, I can think of no other area with such popularity to even compete with it. Once the intangible enters the discussion, as in art and audio, things we don't (yet) know how to measure so it reflects reality reasonably well, we are open to any lunatic with an agenda.

ANYONE can claim this is so and so, and when asked to prove it, all he has to say is that he hears it that way. You try proving that he's a liar. As a result, you have people with access to magazines who are free to promote their own ideas even if they are way off, justifying it by simply saying that's the way he hears it.

The worst of it is, they could be at least partly right. For example, over the years I have established that Mr Alvin Gold (UK reviewer, Hi-Fi Choice at al.) and I seem to have a similar hearing; in most cases, I agree with his findings, and most of the time, the differences are in shades, not in the essence. And vice versa, Mr Ken Kessler and I are completely at odds, what he finds to be fantastic month in and month out I generally find to be not very interesting. Can I, on basis of that, say that Mr Gold is a "good" and Mr Kessler a "bad" reviewer?

And just to add some spice, there were a few occasions when a device was shown to produce rather bad distorion spectra, and yet it sounded good to me nevertheless, just as there were (many more) occasions when something shown to produce very little distortion sounded bland and uninteresting to me.

There is no absolute truth and suprises are guaranteed. In the mid 70ies, my next door neighbour purchased a German made Wega receiver, a typical German product of the day, all black, with rounded edges, very much the style of those times, which had a quasi complementary output stage using 2N3055. Its published specs were way behind their Japanese competitors, yet it sounded WAY better than most Pioneers, Kenwoods and Sansuis of the day.

And just when I thought that way a widlcard, a one-off, here come the Germans with an integrated amp from ASC, model V 5000, also with reasonable but completely unexciting spec sheet and excellent sound I never heard from any Japanese amp until that time. I'm still hunting for that one.

Meanwhile, back at the ranch, even if nobody here seems to even remember a California company called Craig, here they come with a receiver (designed in the USA, manufactured in Japan, just like Marantz) which I remember to be the best receiver I ever heard, bar none, until that time to this day (receiver, mind you, not an amp). A freak purchase by a friend, a spec sheet about average for the day, yet outstanding sound.

Of course, you might not agree upon hearing them, but that's the way I heard them, and it was obviously sufficiently impressive to burn them in my mind to this day, 35+ years later.

We can evolve any method of measurement we like, precise as we like, but in the end, it's all down to ears. First the designer's, and then our own. If these two tastes correspond to each other, we have a great amp/receiver FOR ME. Who knows exactly how my brain (if I have one) correlates it all into one whole?
 
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