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

You do realize I know the circuit you are listening to.

Really good designers understand that carefully chose distortion is much better than no distortion.

Not true. If that's what they think then they are not a really good designer.
Something else is happening and they are blaming it on the zero distortion [settings]. They are using distortion as a partial countermeasure to the real issues. I happen to know exactly what the problem is with that circuit but I don't get involved with other designers stuff.

When I said I don't think the designers are thinking outside the box - I was giving them the benefit of the doubt. Unfortunately they just don't know where to look to resolve the issues in their circuits. That's why things seem to have slowed to a crawl. They have run out of things to try.

A circuit can actually measure zero distortion and still not be zero distortion.Typically a sign wave test does nothing but tell how good a low frequency servo it is. Music is an entirely different matter.

kosst,
I'm not accusing you of being the measurements freak. I'm sorry if you got that impression. I'm trying to show the difference between an amp that measures zero compared to an amp that IS zero.One sounds awful and one sounds incredible. Can you tell me how to measure zero distortion with a music signal as the source?

If you measure the voltage level (of the source) like an orchestra playing normally and you get X amount. (lets say 1/2 volt nominal) Then without changing a beat - add the guy with the triangle at the back of the hall when he adds a single note to the mix. Besides not being able to identify it on a scope - how much additional voltage appears now that the triangle is playing. How big is just the triangle voltage? Millivolts? microvolts? nanovolts? picovolts? This is the range of signals I work with and have mastered control over.

If the entire orchestra was quiet and just left the triangle - it would be seen on a scope as closer to the noise floor. In order to successfully project that object back to the rear of the hall and keep it in focus - you need circuitry with enough sensitivity and resolution to handle the task of rendering that object at that distance. The greater the depth or distance of an object - the harder it is to place it back into the image unscathed.

You can't show me a circuit that does what you claim. You can't because it doesn't exist. If it existed you'd have patented it.

Patience grasshopper - and all will be revealed.