In article , Rob wrote:
I think this is the essence - it's simply not in the toolbox/vocabulary
of most engineers to explain what is reported with certain amplifiers.
There is simply cultural closure on the point that some amplifiers sound
different, especially when 'poor' implementation results in a 'more
accurate' listening experience.

I don't know what you think engineers are, but some of us have quite a good
vocabulary, most of us have ears, and some of us even enjoy listening to
music, otherwise we wouldn't be interested in sound reproduction in the
first place. Sometimes we even get to listen to live music in a concert
hall, so we are well aware of what it ought to sound like.

Anecdotally, I agree with your consideration of AV electronics. One of
the key characteristics of valve amps I've used (mainly class A PP) is
the sense of 3D soundstage. I've never been able to recreate that with
SS - the closest (but nowhere near) is through electronic 'concert
hall'/spatialiser settings on SS amps.

I see others have suggested possible causes, and they could be right, but
here's another. Could the spacious effect you describe (assuming that's
what you mean by a "sense of 3D soundstage") result from microphonic
reverberation in valve electrodes? A bench test without loudspeakers
connected wouldn't reveal this, but if the amplifier is anywhere near the
listening room when in use, its valves, or the baseplate on which they are
mounted, could be acting like microphones.

1) I have no evidence to support my views beyond similar experiences
described by others.

This doesn't necessarily mean the measurements are wrong, or that your
listening experience is wrong. It could be simply that the appropriate
measurements have not yet been made.

Rod.