The Future of Audio Amplification

@tweak1 
That's exactly what I'm saying. Above 1 KHz the power requirements of the amp drop off sharply and the sound quality is entirely dominated by the distortion character below 2 watts. 

@atmasphere 
Nelson specifically warns against using Litz wire with the F5 without putting some caps across the feedback resistors to truncate the high frequency response. He's also said that he makes it a point to limit the high frequency extension of his amps after watching one with F5-like capabilities release the magic smoke on stage when a demonstrator took hold of an improperly grounded volume control box and formed an oscillator. 

Also, have you (as George is implying) had a religious conversion to the world of class D to the point of implementing it in your products?

A fair question, hopefully without the words prototype or breadboarded that no one else has heard.

Cheers George

I know I shouldn't weigh in on this, because I've never heard a Class-D amp, but I am an electronics tech with a First Class license.

Back in the 70's, me and Julian Hirsch declared that we could determine what any amp sounded like by it's specifications.

Julian Hirsch, bless his honest deceased heart, did not have 20-20 hearing, and I had faith in our belief.

In the late 80's, I wandered into a high end emporium in order to discover why people were paying so much more money for stuff that was inferior to mine according to the specifications; did I get an ear full.

I didn't know it, but I could hear a lot better than Julian Hirsch; there was a world of difference between my SS amp, and ARC tube (price as well). There was a big difference between everything I owned, and what I heard. What I heard was worth the difference in price.

Specifications are not as important as they are laid out to be; we can hear what can not be measured; you would be surprised at what some people can hear. In the military, my hearing was measured as exceedingly high. No need to pay for more than you can hear, but I could hear more than what my rig delivered.

I said that in regard to the SS versus Tube amp debate; although I have never heard class D, not only have I heard, but I was religiously devoted to SS amps; that is until I heard a tube ARC. I'm not pushing ARC amps, but I am pushing tube amps.

While a tube pre, and a SS amp power amp will pass; when you go SS all the way, it's a no show for me. I said that to say that I "believe" a class D amp will sound the same as a SS amp, and that's why I know I should not have weighed in on this discussion, but I did; so forgive me for commenting on something I've never heard.

I’m using all tube preamp and amp gear, Class A/B. However, at several audio shows, I heard relatively decent Class D amps. One that stood out was from PranaFidelity. http://pranafidelity.com/index.php/reviews/ Using my CDs in an EAR player and his electronics and speakers, my jazz and classical sounded very enjoyable and I could listen for an extended period of time. It wasn’t as good as my home systems or more expensive systems I heard, but it was musical. More than I can say for any Magico speaker demo I’ve heard in five years. If Class D ever became as good as my big tube amps, I’d be interested but not as of today.

I’ve heard tube preamps (e.g. EAR 912) with big SS amps (Bryston 28 cubed) sound very good, even excellent on demanding speakers. I don’t know if I would like an all SS system though. The ones I’ve heard over the years just lacked something. The PranaFidelity was using a tube (and warm sounding) CD player which may have made the difference using an SS preamp and Class D amp.