Are future improvements in Amp/PreAmps slowing to a crawl?

Progress will be when a "full function" preamp has useful tone controls once again... 

Kosst
 

The problem I've got with the concept of "perfect" or "zero distortion" amps is that it really doesn't matter. How perfect is that amp with a loudspeaker drawing current all out of phase, pumping power back into the amp, and presenting impedances all over the chart? Is it still putting out that perfect signal?

Golly if I had known this I could have given up years ago and saved myself a lot of work.

See here for a nice video of a proper listening test that shows the methodology that is required:
https://vimeo.com/137001237
With some background discussion here:
http://www.harbeth.co.uk/usergroup/forum/the-science-of-audio/the-ground-rules-of-proper-audio-evaluation/2422-how-do-we-grade-audio-electronics-a-strategy

Its not that hard to design an amplifier that is absent the higher ordered harmonics. Such an amp will not use any loop feedback though, as feedback will add harmonic content and IMD of its own regardless of the left/right ’speed’ of the amp (as seen on an oscilloscope). See Norman Crowhurst.

Actually, I fixed that.

I have not yet published it, as I’m waiting to be able to produce an amplifier and sell it to people, before others grab it away and make it their own -to do their shtick of stealing other’s ideas and thunder. I showed it to a ~very~ well known amp designer and explained why/how it works, and he called it, and I quote: "f**king brilliant". I don’t design circuits, per se, but I do understand the overall complex physics in-situ, more than some might.