A very interesting topic. I recently read a paper from Cheever (1989) that's quite interesting. Our aural distortion seem to play a role here. Both from a masking perspective, but also from a musicality and holographic soundstage perspective.
I got the opportunity to borrow a Benchmark AHB2 over a weekend some weeks ago. For listening and measurements. I have an audio measurement system that I use for development so it would be interesting to measure some on the very high performance AHB2 amp. And indeed, it has a very very low distortion. Its a real masterpiece in that sense. And by using forward error correction instead of traditional negative feedback they have reached some incredibly good numbers regarding "traditional" amplifier measurements. That's one part of the coin. The other task was to listen to it. And to me it was not musical or engaging to listen to. But of course transparent, good dynamics and with high resolution.
Papers I have read, own experiments with harmonic distortion and discussions have got me into an idea around distortion. If we add low order harmonics inline with our hearing harmonics we get a masking effect but we also, for us as humans, a natural way to increase harmonics from instruments and voices. Without affecting timbre (I think). This could maybe also explain improved holographic imaging. A least to how I think.
