GaN amplifier from GaN themselves limited supply!!!

As for heat there’s virtually none.

" Again, no heatsink due to high efficiency.s for heat sinking it runs so cool there’s no need for it. Practical MOSFETs take time to switch and during that time, they generate losses in the form of heat and limit how fast you can switch them. GaN transistors aim to solve this problem as these few slides from GaN systems show:"

This statement is false as anyone who has actually worked with GaNFETs knows. Sure, you can make an amp that does not use heatsinks (we didn't add any until we got very close to production) but the simple fact is that GaNFETs do produce heat and if you can't get rid of it, they will fail and often quite dramatically when they do. And you might think that you don't have to worry about shoot thru current heating up the output devices since they switch so fast, but you'll find out differently if you don't include deadtime circuitry to prevent that. But if you're just doing demo and don't run the amp at full output you can get by without heatsinks.

We expect people to abuse our products. So we built the amp so it can be at full output into 4 ohms and it can sit that way all day. That would not be possible without heatsinks!
But for evaluation I'm sure this circuit board is fine. You don't need heatsinks for evaluation applications!

Distortion at high power for a Class-D is incredible

"We see that the distortion is still under control instead of shooting through the roof.!!"

"I don’t think I have ever tested a switching amplifier with this level of frequency independence. Even Class AB linear amps struggle to produce such an absolutely clean response. Amplifiers with high amount of feedback run out of gain at higher frequencies and hence distort more. Not this design."

This has nothing to do with GaNFETs and everything to do with the design. What is being referred to here is sufficient Gain Bandwidth Product, which most amplifiers lack in order to have feedback and consistent distortion numbers at any frequency in the audio spectrum (this BTW is a requirement if the amplifier is expected to sound musical). I've made comments about this aspect elsewhere on this site. What this says is that Amir hasn't tested a lot of class D amps; Bruno Putzeys' designs share this property of consistent distortion at all frequencies, and his designs use MOSFETs.

I know sometimes it's difficult to look past the person based on their comments and interactions with others, but George designed and built the Lightspeed Attenuator which I've owned for over 10 years and consider one of the best values in audio.

@clio09  I agree the Lightspeed is one of the better examples of a passive volume control. To make the devices inside do what they do (which is to say, operate in a linear fashion) takes design skill. Why do you think George designed it- doesn't that seem a bit odd?

unsound
Another Class D that struggles with lower impedances?
Yeah, I know the specific technical arguments for higher impedance speakers, but when it comes to the sonic gestalt, I seem to lean towards those loudspeakers that have lower impedances. Wake me up when there are Class D amps that handle my preferred speakers as well as the better traditional ss amps do. I’m truly hopeful that such Class D amps can be offered at a reasonable cost.

Totally correct Class-D do not like low impedances (yet) that most of the real hiend speakers have.
Also the switching frequency still has to be 4 x higher so it’s filter remnants and phase shift are "well out of the audio band" as Technics did with their impossible to get GaN SE-R1

From Absolute sounds review
For its part, the SE-R1 exhibits the same bold dynamics, staggering detail, and sheer volume of musical information I’m used to getting from my reference CH-Precision A1 monoblocks. Remarkably, this is true even when the Technics amp is being driven by its analog inputs. The sound from both amps is gloriously rich, pure, and grand when the music calls for it. The biggest difference is actually in the Technics’ favor: a more realistic-sounding midrange, thanks to a dollop of sweetness.

and maybe their SR-1000 integrated has also.
https://www.lbtechreviews.com/test/hi-fi/technics-su-r1000

Low impedance stability and drive is the reason why I still like linear amps for my main system.

I do have Hypex NC500 mono blocks though (with no input buffer and massive linear supplies) for the easier to drive second system though. They do well there, but still have that "segregated" uppermid/highs problem all Class-D’s seem have to me (which I’m sure is the switching frequency/phase shift problem) and where that Technics should shine

Cheers George

Also the switching frequency still has to be 4 x higher so it’s filter remnants and phase shift are "well out of the audio band" as Technics did with their GaN SE-R1 and maybe their SR-1000 integrated has also.

This statement is false. If there is sufficient feedback, phase shift at 20KHz will be under 1 degree even if the filter is set at 70KHz.


Also, class D amps if designed as self-oscillating (ex.: Hypex) are inherently stable regardless of load as they are **already** oscillating due to the amount of feedback they employ. You can't somehow get them to oscillate again over the existing oscillation....

Yeah, just throw more bandaid fix feedback at it. (just like the zero auto former you push for the OTL’s into hard loads)

Everyone know too much feedback is detrimental to the sound, that’s why that GaN by GaN Class-D measured by Amirm had "very little feedback on it" programed from the owner, for the sake good sound, but of not measuring too well in certain parameters. (get with the program) and you and your mate stop putting      on everything that’s in opposition to what you’ve got coming, not just on this thread I’ve seen but others too!

And btw you can’t cure this kind of -75 degrees! of phase shift (red) with      loads of feedback https://ibb.co/S06J7hf only a 4 x higher switching frequency will move that up out of the audio band!!!