Andre Jute wrote:
Phil wrote:
We're
not talking about "-30 degrees at 20 KHz," we're talking *dynamic* phase
shifting, the kind that makes a Crown preamp bite your ears off, while
testing at 0.0001% THD.
Let's hear some more about this dynamic phase shift that pours a pint
of vinegar into a Crown preamp. I'm not overimpressed with vanishign
THD but this is an amazing explanation for why so many silicon amps,
and not a few tube amps, sound like ****.
Andre Jute
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Pretty much what Patrick said, although I need to reply in the original
thread. What Matti Otala PROVED -- and Dr. Ottala was up there with
Richard Heyser, not just a professor, but the Director of the Technical
Research Center of Finland, and the guy who published many of the
original papers on TIM (transient Intermodulation Distortion), so what
he said should at least *intially* be taken seriously -- was that the
amplitude distortions of the open loop are transformed into phase
distortions of the closed loop, where the low frequency signals phase
modulate the high frequency signals. I *think* this means that the high
frequency signals move back and forward in time in the presense of low
frequency signals, something that is actually quite difficult to
measure, although all too easy to hear. It has some rather interesting
implications about feedback, and the optimum configurations(?) of
feedback (what's the word that refers to the various types of feedback
electrical circuits?), which I wil hopefully get to sometime soon. In
"The Audio Critic," Vol 2, #2, 1979, p 37, Peter Aczel said Otala's
technical paper was to be delivered on Feb. 25, 1980, at the 65th
convention of teh AES in London. I assume that the paper was published
soon afterward in the JAES, but I'm not certain. Guess I should go by
the UT library and have a look! (Hey, what's the use of living in the
"liberal armpit" of Texas -- Austin -- if you don't make use of its
assets? ;-)
Phil