GaN-based Class D power amps

Some more info that come to the net, also i may have mentioned, that TI Texas Instruments (who also own Burr Brown) have now the rights to manufacture GaN semiconductors.

"EPC’s enhancement-mode GaN (eGaN) transistors switch up to ten times faster than silicon MOSFETs, with ‘zero’ stored charge. The increased switching speed of eGaN FETs allows amplifier designers to increase PWM switching frequencies, reduce dead-time, and drastically reduce feedback; producing a sound quality previously limited to large, complex, heavy Class-A amplifier systems.

Demonstrating the superior performance of eGaN technology with their eGaNAMP2016 amplifier, Elegant Audio Solutions of Austin, Texas, has produced an amplifier capable of a continuous power output of 200 Watts into an 8Ω, or 400 Watts into a 4Ω speaker load, with THD+N as low as 0.005% and very low feedback."

https://m.eet.com/images/planetanalog/2016/10/564363/Image-4.jpg

Elegant Audio Solutions’ eGaNAMP2016 Class D amplifier with audiophile level audio performance.

Moreover, this is done without the need for a heat sink and eGaN-based amplifier can plug directly into the standard amplifier implementation of many existing systems.

In addition, the higher output filter frequency makes output filter design less expensive and the higher switching frequency makes EMI/EMC compliance much easier to accomplish.

As noted, since the switching edges of the eGaN FET are cleaner, and introduce less ringing With a good layout, overshoot and ringing can be virtually eliminated [3]. With the reduction in both the output filter costs and the virtual elimination of heat sink costs, the eGaN FET-based high-definition audio system will not only sound much better, but will be much smaller, and have a lower system-level cost than the classic MOSFET-based systems.

Cheers George

Regarding power output of the in production GaN-based class D amps, I’ve been criticized for posting what is from the manufacturers’ own websites. So this is my last attempt to compare their respective outputs:

ADG Vivace: 200W into 4 ohms with 0.1% THD using a 1kHz signal

Technics SE-R1: 300WPC into 4 ohms with 0.5% THD using a 1kHz signal

Merrill 118: 800W into 4 ohms (no THD or frequency signal data specified).

Every manufacturer, has a different approach about how to provide (a bigger) number, when related to the output power.
It is the main number that attracts first attention, and for the most part actually it means not very much, but yet that is why the temptation (thanks to the lack of industry standards) to find a point in the THD vs Frequency chart as favorable as possible, and get it as big as possible.  
We have chosen to provide a number, within the characteristics of the design of the GaNTube, that still has some more meaning, in relation to a power level that can be delivered within reasonable quality (low distortion) and generate a "ears-drum safe" sonic pressure, if ever used.
With a 100W input signal, a speaker with even low efficiency, let's say of 87db at 1W/m., can generate a pressure of almost 110db...so...

By the way, comparing the power specs, it seems to me that the only way to get to that power level, considering the GaN MOSFETs available in the market, both Technics and Merrill amps are likely adopting an internal bridge configuration, for the power stage.
In other words, with a bridge configuration, the power would have be 4x. (The load sees twice the voltage swing, and since P=V^2/R if V is double then P is 4x).
The Power stage integrated into the GaNTube is not in bridge mode, it is a single stage, and for whoever is curious, uses a custom integrated half-bridge GaN Mosfet made by IR (now Infineon).

Also, I would like to share something more. When the idea of the Vivace was conceived, so to speak, we choose to go with an unique design, both for the technical and the aesthetic one.
That decision was made because we wanted to convey the message that a ClassD amp can sound better than the best classic Tube amp, and actually look very nice too and different (not just like another metal box of exaggerated dimension).
The aim was in principle to liberate the Class D topology from the "stigma" it has been carry-over for way too long, and for sure now, at least with GaN, without any foundation or (de-) merit; actually all the contrary. And it seems it is finally happening.
In any case, what I found peculiar too, is that from all these comments, now so many, it seems only very few people actually have had the opportunity to do some true comparative listening tests.
By reading the comments, whoever has done it, more and more it sounds to me like someone that "...has seen the light" (sorry for paraphrasing St.Paul...but...)
So my suggestion is...type less and listen more...go get to listen to these amps!

AGD

 Fluoride in our (US) toothpaste is nasty, too. Feds have no problem feeding the health benefit bs line to us. Lol

Yes, but it is peddled as a benefit, whereas power consumption cannot be disputed

:((((

I should never have checked out this thread.

Reading Merrills' amp reviews/comments I am so disheartened that the commenters own amps (including Merrill's pre Element series) significantly more expensive than anything I can dream about being so much better. Even the AGD Vivacies (which also have outstanding reviews) are way out of reach