How close to the real thing?

Atmasphere,

I am adamant that the rules of human hearing trump all other considerations

Agree 100%.

So the effect in an amplifier with loop feedback is that low level detail will be truncated and this is readily audible (IME) as a loss of ambient and soundstage information

Unfortunately, disagree 100%. IF the feedback is done badly or is extremely minimal in its effect then that may be the result. I agree that "low level detail is truncated" is often the way distortion manifests, but my experience is that this is lousy power supplies and a myriad of other subtle mechanisms causing problems, which insufficient feedback may struggle to compensate for, but only ends up making things worse. In other words, the overall engineering of EVERYTHING has to be got right, and then that "harmonic noise floor" you speak of will be reduced to a level well below audibility

Frank

Look at a concert. Any concert. Chances are they have horn tweeters and midrange speakers and a big woofer in a speaker array. You get NO IMAGING. Stereo is a imaging experience that make one think he is in a studio not a hall,if you want a loud wall of sound get horn speakers. If you want the studio sound get non horn.

Vernneal, consider that at a concert imaging in the PA is not important. You may well be listening to mono.

Horns have no trouble doing imaging, that's for sure. There are other threads that have covered this subject.

Fas42, I agree completely about the power supplies. In fact I run a separate power supply with its own power transformer for the driver section of our amplifiers. The idea is to prevent any sort of noise that might occur in the output section from having any influence on the driver. This is one of the ways to really reduce IM distortion, as the power supply noise issues are usually modulation issues, but the effect is less pronounced for THD.

And I also agree that the engineering has to be right- you are absolutely correct that there are a ton of variables that affect any design and its easy for a problem in just one of those variables to completely overshadow other design parameters. IMO right here is where you encounter the human element in design.

Y'all have a nice holiday!!

Well, if you play a musical instrument vs. listen to sound, they are obviously very different things!
IMO nothing can aproach the connection you get to the music with playing - even listening in a concert hall. Any electronic copy and reproduction will always fall short.

Mikewerner, while I agree, this doesn't mean that one cannot get closer. I have heard speakers that are very easy to listen to but which are not at all realistic sounding.