GaN FET Amps vs. Traditional Class D Amps

it's easy enough to find or build decent power supplies and input buffer circuits for them. And not every GanFET has a great power supply or input circuit. Just sayin. 

@ericrhodes1 You'd think!!  

I regard it as a sad state of affairs that there are so many amps with good modules that seem to have poor power supplies and/or input buffers. A lot of class D amps in the last 25 years really didn't sound that great, especially in the bass, and as far as I can make out the reason seems to be that since class D is so much more efficient, whoever put the module in the box thought that also meant the amp didn't need a power supply to be as beefy.

But a class D amp power supply has to be able to handle almost no load when the amp is at idle and not sag when the amp is trying to make full power. Its a pretty big ask. On that account we found that if a switching supply is used, if you really want to make it work right it should be tailored for the application. IOW you can't just buy an off the shelf SMPS and expect it to work unless you really vet it carefully. 

WRT to the input buffer I've seen some pretty wonky stuff as well. 

The really variable comments you see about different class D amps using the same module backs this up. Its been my personal experience as well.

@atmasphere Ya, well in the last few years, there’s been some real standouts in this regard. But it requires a keen eye to find, I’ll hand you that. 

But it requires a keen eye to find, I’ll hand you that. 

@ericrhodes1 IMO it should not. But here we are.

You guys may be right but I remain scarred by my dive into Bruno Putzeys’ NC1200 amps that replaced a pair of pretty good sounding Class A monos and which, at the end of the day, simply didn’t sound real to me.  All of the most satisfying (long-term) amplifiers I have owned were big Class AB amps. 

The OP said:

“Whenever I see a write up on GaN FET based amplifiers they are always compared against class A or class A/B amps.”

I suspect that is a marketing thing as they desperately want to say, “these amps sound as good or better than Class A!”

Regarding GanFET, it seems the concept received more publicity before the amplifiers actually began production and they are now sort of, just another Class D amp. Maybe I need to look harder but based on the reviews I have seen and user posts, my impression is that they are good, to maybe better than good (in the right set-up), but not necessarily as great as the pre-release hype would have had us believe.  However, I admittedly haven’t had a set in my system, partially because I need more than 100 wpc.

There is probably some truth to your comments about better power supplies, as shown by the Theta Digital Prometheus, Class D (Putzeys’ NC1200 modules) monoblocks designed by David Reich with a big-ass linear power supply (review link) .Larry Greenhill raved over them in Stereophile and John Atkinson said,

“The measured performance of Theta Digital’s Prometheus is superb, even for an amplifiers with a class-D output stage.”

@mitch2 

I suspect that is a marketing thing as they desperately want to say, “these amps sound as good or better than Class A!”

I think its worth it to compare if you can! I ran class A triode OTLs which my class D amps replaced and I've not looked back. So not just class A, but triode as well...