GaN FET Amps vs. Traditional Class D Amps

I can't say enough good things about the Atma-Sphere GaNFET Class D monoblocks, which have been in my system for the past four months. They have been a big part of the transformation of my listening experience.

The A-S monos replaced a pair of excellent PS Audio M700 class D monoblocks, which used the ICE modules along with some fine-tuning of the output stage to improve the musicality of those amps. For me, the M700s had earlier replaced the classic Pass-designed Adcom 555 stereo class A/B amp, which sounded smooth, but emotionally subdued in comparison to the M700s.

In comparison to the M700 ICE monos, the A-S GaNFET monos sound much more transparent and smooth in the highs and midrange. When paired with the planar-magnetic drivers in my new PS Audio FR10 speakers (acquired in January), the A-S monos have incredible synergy. Their amazing transparency and smoothness make them a perfect match for the low-distortion drivers in the FR10 speakers. This is the sound that is often described as open and transparent without harshness.

The low frequencies are also outstanding with the A-S monos, but they took a bit longer to develop in my evolving audio system. With a recent upgrade in my streaming gear to the Innuos Pulsar streamer, I am now also hearing the deepest and most natural-sounding bass I have ever heard in my home system. (Listen to Joe Morello's opening drum solo on "Take Five" from the album "Morello Standard Time" and you'll know what I'm listening to.)

Anyone who questions the musicality of GaNFET Class D should listen to the Atma-Sphere Class D matched with the right sources and speakers. The realism is amazing! 

I have been listening to the Mola Mola ossetra mono amps for the month. This is seriously excellent sound paired with the Perlisten s7t Limited edition speakers. The soundstage, imaging and separation of instruments is astounding. There is a lot of ( I never heard that before) with these amps. Microdynamics. This is in comparison to the Dartzeel 108 m2 which I listen to for many years.  

@snook2 Those Mola Mola amps are serous Class D. You’ll never see a GaNFET go toe to toe with high end Class D amps like Eigentakt’s or the best NCores let alone a Mola Mola. I dare anyone to A/B these. The only claim to fame I ever here is "GanFET technology offers several advantages over ’traditional’ Class D amplifiers." Bruno Putzeys has overcome any advantage GaN has in switching speed. And the amps can be built for much cheaper with higher wattage than Gan’s. "Traditional Class D" found in mainstream integrateds and even some high priced name salon manufacturers won’t win in a fair fight. But there’s a few very good Class D, when well implemented, can sound as good for half the price and double the wattage of overpriced GanFET amps. 

I'm with Tubeguy recommending Orchard Audio.  I demo'd this with friends and it was outstanding.  I have heard Atmasphere's Class D monos at audio show and they sounded fantastic.  No tubes to replace, no heat, and wonderfully melodic music.  I think GaN technology clearly brings this mode of amplification to prime time.   https://orchardaudio.com/shop/starkrismon_stereo_ultra_500w_stereo_amp/

You’ll never see a GaNFET go toe to toe with high end Class D amps like Eigentakt’s or the best NCores let alone a Mola Mola. I dare anyone to A/B these. The only claim to fame I ever here is "GanFET technology offers several advantages over ’traditional’ Class D amplifiers."

@ericrhodes1 In terms of distortion you are correct although its nothing to do with the output devices. It has everything to do with the patents Bruno controls. 

But GaNFETs do have a nice advantage over MOSFETs in that they are so much faster, with a lower turn on resistance, so its impractical for the device to have leads. So they are very thin and usually 1/4th the size of a postage stamp or less.

With no leads (just solder pads) it is far easier to control parasitic inductance on the circuit board! This allows the design to be lower noise. This is important since any switching noise that leaks out of the amp (as Bruno has pointed out) can interfere with other components in the system (essentially acting as Radio Frequency Interference). So its paramount you can keep that noise down so other components can sound/perform their best! 

In our class D for example the main source of noise is actually the power rectifiers in the power supply- not the module (which is of our own design). The rectifier noise was easy to suppress; as a result our class D amps radiate (thru the ground, AC line and through the air) less noise than many tube amplifiers. 

A secondary issue but one to be concerned about is the fact that many class D amps based on Bruno's modules don't have adequate power supplies or input buffer circuits since the modules are sold without those. Both are vital to allow the amp to perform properly. 

So even though the Purifi modules are the lowest distortion class D modules, that isn't the same as 'all amps using Purifi modules are equal'. So as a result, GaNFET amps can go toe to toe with amps using those modules. 

What this means is you still have to listen to the particular class D choice you might have in mind. Not supposed to work that way IMO but here we are.