"Eiron" wrote

An oscilloscope will tell me the gain and phase shift at various
frequencies when I feed the amp with a sine wave.

Scopes are fine for rough amplitude and phase measurements, but for the sort
of precision measurements you would need to obtain the information you are
talking about they really don't cut the mustard.

Have you seen any manufacturers spec sheets that go into such detail?

Yes I have, for the more up-market and professional gear. I reckon that's
your best bet, unless you can lay your hands on a proper swept-frequency
analyser.

The real question, I suppose, is why do you want to know? Is this just idle
curiosity, or do you have some dark purpose?

David.