Objectivism ruled and high negative feedback gave vanishingly low THD and IM numbers. However, the resulting sound quality got worse, not better. TIM distortion was discovered, feedback was dialed back, and the importance of listening was once again proved.
This statement isn't entirely correct! TIM was simply caused by part of the amplifier being outside the feedback loop. With regards to 'high feedback' there were none in the 1970s that had enough Gain Bandwidth Product to support that feedback at high frequencies- so at higher frequencies the feedback fell off and distortion increased- resulting in the 'harsh and bright' solid state sound that has plagued solid state amps since their inception.
his statement was to me that he has heard amps that compete - so since I cannot get a hold of his amps - I am asking him to provide me with his experience based upon his response to me.
To date, we have not heard a class D amplifier that competes in sound quality. We are open to hear something that comes close but not yet to our ears.
"I have. FWIW class D amps vary at least as much in sound as tube amps do."
The amp that convinced me that we needed to being working with class D was a Cherry amp. I've not heard the Orchard but it seems to get very nice comments. A couple of customers have the AGD amplifier and are very happy with them.
The bottom line is you can't say if you've heard one you've heard them all! I've heard some that I had to really ask if the manufacturer was serious (that was a long time ago).