I stand by the intent of my original statement:
Amps seem to sound more sensitive to impedance issues to me than the math otherwise suggests.
@erik_squires I was not contesting this, FWIW.
There are far far too many other factors at play including open-loop bandwidth, compensation network, or just to make it simple, transfer function including load to simplify to an amount of feedback to equate to a particular sound.
Your simplification suggests a marginally unstable system as opposed to an over-damped system.
@heaudio123
Correct.
In order to present a nutshell explanation of how feedback is problematic (and also how to use it) the explanation has to be simplified and as much as possible use layman’s terms.
Open-loop bandwidth of course plays directly into gain bandwidth product, and compensation networks inside the feedback network itself and also in the actual signal path are of course important in any proper amplifier design. But the essence of my point is simply this:
If an amplifier has enough feedback, it won’t be bright and harsh, whether tube or solid state. Historically we’ve not seen really such an amplifier- that is why tubes are still around!
IMO most amplifier designers don’t really know how to design a proper feedback loop (as you know its far more than just a simple resistor). Meanwhile the test and measurement folks seem to realize there’s some dirt to sweep under the carpet which is why you rarely see THD analysis with the fundamental much more than 100Hz, with harmonics in the ear’s most sensitive region simply not displayed.
