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Re: kind of a long answer

Hi Tom,
Thanks for the detailed explanation.

I have a question for you regarding some interesting things I have noticed looking at amplifier mesurements. I noticed that with many amps using negative feedback (they are easy to spot by looking at the THD vs. Power output curve) they have funny behavior when you see a plot of damping factor vs. frequency. Specifically, the damping factor stays uniformly high until about 1Khz (sometimes even lower sometimes a bit higher) where it then drops like a stone.

Now if you look at the THD vs. Frequency plot you will invariably see a rise in the distortion of the amp that mirrors the drop in damping factor. Based on this observation it seems clear to me that the feedback loop in these amps is not fast enough to completely correct the signal anymore and not only does the output impedance go up sharply so does the distortion (sometimes 100 fold over the lower frequency distortion).

Maybe I am crazy but to me this looks as if the feedback is failing at high frequencies and that an increase in high order distortion is almost certain and possibly resulting in what makes most ss amps sound , grainy, harsh, or sterile. I can imagine the situation only gets worse if back EMF is added to the feedback signal.

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