New Class D amplifiers

@erictal4075

See Bruno Putzey’s comments regarding GaN devices usage here:
 

As for better performing amps, see the new Hypex NCx, nilai500 and the Purifi amp modules.

GaN is the flavor of the day. Most of the amps using it are leaning on the marketing and claims of "new and improved". It’s only an improvement if you are clever enough to implement it in a way that exploits its advantages over traditional silicon and so far few are actually accomplishing that. In fact, many GaN amplifiers out, from Peachtree and LSA for example, use old class d designs without post filter feedback, resulting in load dependent frequency response. Most modern class d amps have post filter feedback and flat frequency response with load. Performance wise, load dependent response is a step backwards.

No rational reason whatsoever, from a performance standpoint, to spend $5000 and more for a class d amp. Of course if someone wants to spend $4000 for a flashy case to get performance that can be beaten by a $1000 Hypex or Purifi amp, it's their money to squander...

The advantage that GaNFETs have is they have very low parasitic inductance. What this means is its easier to build a module that is low noise- and by noise, I mean the kind that radiates from the module over the air and thru the AC power. Its important to keep switching noise and parasitic noise low because it can mess with other gear and affect its performance. As an example, our class D amp makes less noise on the AC line than most tube amps. In terms of noise that it makes in the loudspeaker itself, 90% of that comes from the input buffer circuit, but even then is obviously quieter than tube amplifiers (I use horns at home FWIW).

We've been docked a bit on account of the cost of our class D (which is cheaper than most of our tube products). We built it to be rugged (so it will ship without damage), to last decades, to be easily repaired and updated and to that end it has a fairly expensive chassis and power supply. It would actually be more expensive if we used someone else's module.

to last decades, to be easily repaired and updated

Does anyone actually think anyone will be using the same class d amp in 20-30 years? With the way the technology is still evolving, I find that bordering on pure fantasy. I see no reason why having something that is easily repaired (what can be easier than swapping out a module?) or updated should add significantly to the price.

Linear power supplies are have for the most part been superseded by smps. With all the class d amps on the market using smps successfully for a decade or two now, there is enough data to show they are in general reliable and that their performance is more than satisfactory. But then, nothing says quality like a big, heavy transformer and flashy expensive case, especially to those who are willing to pay a premium for racing stripes and metallic paint. Vrooom!

All I can say is I remember when a certain member of this forum would simply not leave anyone who liked Class D alone, and insisted that Class D would finally get listenable with GaN. 

Hahahahaha.

Don't get me wrong, I'm all for technological improvements, but I see more clear innovation and utility in Atmasphere's amps than in doing the same old thing with GaN (apologies to you Technics fans!)

GaN is good check out Wolfspeed.  If you are really interested in ADG, I own Audios deal with Alberto the designer.  Great guy.  He will respond to questions, interest on the ADG web site.