It seems to me that we would want to establish first, as you say conclusively, that there IS an audible difference between the two cases. Speculating on the causes of something we don't know is true doesn't seem productive.
jan didden
Frankly speaking, I do not understand. The 3rd, 5th and 7th are more than -110dB below fundamental, at amplitude near to clipping. For lower amplitude 5th and 7th disappear. Most low feedback and no-feedback (so-called) designs have 5th and 7th higher than -110dB. Do not you want for me to link Stereophile results, I guess - it would start flame only.
I don't know the specific case graphed by PMA, but in general, lower order distortion is dominant at low levels and higher order terms become visible at higher levels of output or lower impedance loading (higher levels of current). That is why serious designers usually test at 4 ohms or less, to bring this out. CLIPPING is a separate problem, as is CROSSOVER DISTORTION. These throw out most mathematical estimates, so that you have to test to know the true amount of distortion with level. This comes from classical analog distortion math in the prediction of harmonics from a non-linearity. This is taught in analog engineering classes, at the senior and graduate level, at least where I learned it above and beyond a few ready made equations.
I spent some time hunting around for the original document you cited, to gain some kind of context. I didn't find it, but looked through several other of Bruno's papers instead. The long and the short of it is - those papers are not listening evidence for the sound of feedback.
Feedback is associated with a falling loop gain with frequency, that often leads to rising THD with frequency. The sound there is not the sound of feedback, its the sound of rising THD with frequency, and only when the THD is at a level to be audible. Not at all contentious. If Bruno believed for one moment that feedback sounded bad, why would he use it in his own products and recommend others to do the same when giving seminars?
In contrast to providing any support at all for the view that 'feedback sucks', Bruno criticizes this as a belief without foundation in one of his recent AES papers. The paper can be found here: http://www.hypex.nl/docs/allamps%20hypex%20layout.pdf
(the relevant section for our current discussion is 3. The Handicap Game)
john curl said:
Curious John - may I ask why?
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Hope it wasn't my fault. I've lost the energy for protracted debate of these same issues ad nauseum.
I am not insulting the guy's ears, it is his 'attitude' that tends to need adjusting, on occasion. Everybody knows what he is like. I do read just about anything that I can get ahold of from him. Great circuit theorist.
I have never found amateur or professional musicians the best candidates for judging hi fi. It has to do with left brain dominance of the listening experience, over the right brain. Now, we have something to debate about!
You know, Scott, I still have your excellent simulation of DA in capacitors from 25 years ago, what happened? You used to believe in improving hi fi.
I have never found amateur or professional musicians the best candidates for judging hi fi. It has to do with left brain dominance of the listening experience, over the right brain. Now, we have something to debate about!
You know, Scott, I still have your excellent simulation of DA in capacitors from 25 years ago, what happened? You used to believe in improving hi fi.
I'm interested in what really matters, audio at the highest end is an indulgence that certain people value. Let's not put it above the march of pure engineering advances in other fields. I have said it before please point out systems that operate at the highest resolutions that need all this snake oil. Cat scanners, PET scanners, Ultra sound, the list goes on, absolutely none of this nonsense applies.
Nonsense? What nonsense? I will have you know that 25 years ago when I designed laser electronics, I did not find it to take the sort of finesse that I have to put into audio. I suspect that PET scanners don't need it either. You appear to have no idea what the military aerospace contractors do to make exotic products, because they won't tell you, but Vishay resistors were not made first for audio, for example.
For example, cryoing was invented by the military. Did you know that? Yes, back in WW1 and used extensively in WW2. Can you or anyone here IMAGINE what the advanced military circuitry today is like? What efforts they most likely do, to get it right? I get a few hints, now and then, when they declassify something, such as Aluminum Oxynitride, ALON, or 'transparent aluminum'.
SY has advanced military technology in front of him, and he can't even recognize it. I never fail to be amazed at my critics here.
For example, cryoing was invented by the military. Did you know that? Yes, back in WW1 and used extensively in WW2. Can you or anyone here IMAGINE what the advanced military circuitry today is like? What efforts they most likely do, to get it right? I get a few hints, now and then, when they declassify something, such as Aluminum Oxynitride, ALON, or 'transparent aluminum'.
SY has advanced military technology in front of him, and he can't even recognize it. I never fail to be amazed at my critics here.
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Objectivity has the downside that it can only lead to an objective
price/perfs ratio if the logic is to be followed extensively.
Money only lies where subjectivity is, as price/perfs is then completely
removed of the price fixation equation...
Well, subjectivity allow higher average selling price while
having no obligation of technical e'xplanation to explain
this other than such claims as "NFB do not sound good"...
Pavel,
Just thought about something. You presented two measurements, saying that 'the only difference is the feedback factor'. How can that be? Does that mean that thetwo amps have different gains? If not, how did you accomplish keeping the same gain with different feedback factors? In other words, what else was different ?
jan didden
Welll, 'my' requirements are really simple; it's the type of test that is done in a scientific way all the time, all over the world, in many a discipline.
As far as I understand you, the reason you do not accept that accepted methodology it is that the test doesn't lead to the results that you think it should. What can I do?
jan didden
Well, even my IC based JC-3 phono stage uses Rel. RT polystyrene. In fact, I INSIST on it. You can revert to Mylar, or how about ceramic, Scott? There must be some pretty good non-NPO ceramics that kind of work! Personally, I am hoping to remove the ceramic coupling and high frequency filter caps from my Sony am-fm radio, because I am under some delusion that I can hear them.
Jan, you should just ignore Charles and me. We have nothing to offer you. I hear what I hear, as I have done for the last 50 years, without needing proof of some kind that I actually hear differences between acoustic guitars of the same manufacture, or electronics proporting to do the same task.
Jan, you should just ignore Charles and me. We have nothing to offer you. I hear what I hear, as I have done for the last 50 years, without needing proof of some kind that I actually hear differences between acoustic guitars of the same manufacture, or electronics proporting to do the same task.
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