[Arny Krueger]

"Phil" wrote in message

Eeyore wrote:

For a 20kHz signal of say 2V peak amplitude that means a
slew rate of 0.25 V/us ! Even a rubbish 741 or 1458 can
manage that !

Agreed.

Given that modern audio op-amps are capable of slew
rates of ~ 10V/us - you're never even remotely close to
slew limited anything.

Agreed.

I was just looking at the specs for a modern op amp that I think TI or
National is trying to popularize, and the SR was more like 100 V/uS

Well, remember, the maximum slew rate found in audio
signals is much greater than what a theoretical 20 KHz
signal is going to supply,

OK, let's totally lose our minds and say that it is 10 times as much. That
makes 2.5 V/uS, which is still only 25% of the capabilities of ca.-1980s op
amp.

BTW here's a hint - the slew rate at the output of any digital player is
limited to voltages along the lines of what Graham came up with in his
calculations. Why we laugh when people "upgrade" the outputs of CD players
by putting in op amps with rediculously high slew rates? ;-)

and not all power amps, with
their big, slow, output transistors, are going to be as
fast as even a 741.

Wrong again. It's hard to find a modern power amp that slews even just 10
times faster than a 741. Most do far better than that.

Plus, the point of Matti's work is
that problems begin to appear at all levels below the
theoretical "breakthrough" point of TIM/SID.

See my previous ludicrously tough example that included a 10:1 safety margin
and was still hitting only 25% of the capabilities of 25-year-old
technology.

In any case,
the topic here is not whether most amps have sufficient
slew rate -- I assume that *most* good amps do -- but
rather about Otala's proof that a feedback amp's
"correction" of an amplitude distortion of the open loop
phase shifts the high frequency components in the closed
loop.

Which is wrong.

I am currently discussing this in the "Negative
Feedback in Triodes: The Logical and Experimental Proof"
thread from 8/15, so if you're interested, look there
(articles posted on 9/6).

I can't bear to look at that thread again Phil, because you took such a
merciless licking from just about everybody.