The Future of Audio Amplification

I find Brunos definitions kind of useless.
Most Class D have no Analog to Digital Conversion (ADC) stage, but do have comparators. Hence the feedback required.

Actually the use of a comparator has nothing to do with whether feedback is needed or not. If its a cheap comparator with offset problems feedback is probably a good idea, but IME the resulting amp will have the problems that many class D detractors (often, myself included) complain about.

michaelgreenaudio
  Thanks for the link George.

That's ok Michael, here another little read you may be interested in, it from the AES Berlin White Paper presented by EPC's (GaN) Steve Colino and  Alex Lidow inventor of the Power Mosfet all those years ago.  

EPC's White Paper "excerpt" on GaN technology used in the Technics SE-R1 and Merrill Element 118:  

"You can increase switching frequency and audio bandwidth to reduce the filtering cost. The choice in optimal switching frequency is always a trade-off in EMI profile, efficiency and audio performance. The ability to use much higher switching frequencies before compromising efficiency allows for a much range within which to make this trade-off. The result is a more optimized audio solution without fear of Thermal or EMI boundaries.
Most importantly, you will be providing, by far, the most realistic listening experience to your customer in a Class-D system."

This is why you'll see, Class-D's with heat sinks inside for each channel like the Technics SE-R1, if they've used the higher 1.5mhz switching speed available to them to use with the GaN.
https://abm-website-assets.s3.amazonaws.com/ecnmag.com/s3fs-public/embedded_image/2018/02/figure1.PN...

I also asked EPC by email what manufactures other than Technics and Merrill Audio are using or developing Class-D amp with their GaN technology, they replied today, other than the two I mentioned, they said: 

" We are unable to reveal due to the Non-Disclosure Agreement (NDA) with our customers.
But I can assure you that there are several customers globally, developing with eGaN FETs for Audio applications, primarily due to the benefits it offers."

Finally it seems Class-D has stepped it up in a big way in technology because of EPC's GaN technology, and maybe put up a fight against the very best of linear amps for sound quality in the mids and highs, I think they already have that mantle for bass performance. 

Cheers George

Here is another GaN amp to add to the list...

http://agdproduction.com/gantube.html

 aolmrd1241 
Here is another GaN amp to add to the list...

You can read more about it in these publication reviews http://agdproduction.com/news.html

Yeah?? I don’t know about that one, jury’s still out, till we hear more about it.
Looks to me like a bit of a furphy to gain an edge with the tube brigade, and cashing in on new technology. Might still sound great.

I ask, why put solid state components inside an old 6550 vacuum tube envelope, bet it’s not vacuum’ed back out and sealed again either.
Still it may sound good, just the whole gutted tube thing, stuffed with solid state, and still using all the tube pins as power/current transmitting contacts????

PS: OK he’s shown all his cards, in this statement

" Company founder Alberto Guerra admitted that he did it largely for the sake of visual aesthetics. “Otherwise a class-D amp just looks like a box,” he said. The amp uses gallium nitride MOSFET output transistors, which Guerra says switch faster and allow the amp to have a noise floor in the -120 to -130dB range. Power is rated at 200W into 4 ohms."

Good on him, I think it was a bad move to do it. (must have been an Italian brain snap to do the tube thing, they do make some of the best and worst cars also)



Cheers George

Bit like D’Agostino, putting "Big Ben" on the front of his amps????
A Cadillac "Superfly" thing???
https://i1.wp.com/dirtyoldcars.com/wp-content/uploads/2017/07/Cadillac-1985-Eldorado-super-fly-1.jpg...

Cheers George