I have always had the belief that the combination of gear, as to how they operate with each other does effect the sound. Especially the amp/speaker combo.
Yes, that is what it is, just a belief.
Likewise, the quality of an amp's circuitry and quality of components can also make a difference.
Or not. Dr. Rich has examined different topologies many years ago and how components sound. Doubt you would accept the results.
Yes, it was published at AES.
Too many people think that just because two, three, four amps all have the same FR (or close enough to each other) HAVE to sound the same is wrong. As has been shown in this article.
Well, a few amps can sound different, but the only way to find out if one wants to know is a controlled test, period.
I have stated many times that FR is not all that matters in the sound of any given amp.
No, there are a few other parameters that can be audible but FR is telling indeed.
I know that things that can not be measured on the bench, can be heard as differences between amps.
No you cannot know this just believe in it. Knowing comes from rigorous discovery testings which I doubt you have conducted.
I listen to music with my ears, not with an oscilloscope, or via a computer graph. As such, I don't really care what any given amp might measure. I determine what amps and other gear I use with my ears, not some graph.
Oh, but if you want to know, you need to listen under controlled conditions as you don't need to see or know to hear.