GaN-based Class D power amps

Transistors inherently have a lot of capacitance. This is the cause of the slow turn off. The capacitance in the transistors (MOSFETs in particular) keep the charge going even though the voltage has been removed. This causes running at the top and over shoot. Hence the hard edge of Class D also. Class D typically operates at 400kHz and so RF design methodology has to now take place on the circuit boards, wires, components and the whole design. A simple item like having a trace on the top of the board and the bottom of the board created a capacitor that could now affect the sound.

The overshoot is a common cause of the hard edge found in a lot of solid-state equipment. That is because the speed of the solid-state transistor led to all sorts of parasitic capacitance's to come alive. As mentioned prior, board capacitance, component capacitance, even the via’s on a circuit board make a difference now. The overshoot would suppose the frequency be in the 100kHz or higher. RF design is a key factor in Class D and in making good solid stage equipment.

What GaN (Gallium Nitride on silicon or Gallium Nitride on Silicon Carbide provide is
1. Ultra-fast switching speeds
2. Almost no overshoot and ring
3. Minuscule parasitic capacitance on the device.
4. Much greater efficiency of operation.

I can only speak for the Merrill Audio amplifiers at this point.
1. There is zero dead time. So it is smooth and you cannot tell or scope any switching.
2. There is zero feedback. Since we don’t have to correct for distortion or overshoot or deadtime. This results in pure detail and air (assuming the track has all of this recorded in it). The difference is quite stunning.
3. There is miniscule parasitic capacitance and inductance. There are probably have more capacitance in interconnects.
4. The wasted energy is minimized and the design is very efficient. Hence the amplifier operates at a stable low temperature, keeping all components around it operating at a low temperature also. This temperature stability means the operating amplifier approaches theoretical design. There is not thermal compensation required or degradation of components due to heat or thermal gradients of components to worry about. While green is a side benefit, the actual benefit is stable operation of components. This is big as inductors, capacitors and resistors have heat coefficients (positive and negative) and have different values at different temperatures.
From a sonics standpoint, the new Merrill Audio ELEMENT series are easily an order of magnitude better than the VERITAS. But don’t take my word for it, go listen to them yourself. Take your amplifier and do a direct A/B comparison.

GaN transistors – first commercially available in 2010, will certainly become more pervasive as the costs come down. GaN material was used in LED’s for over 2 decades.

GaN transistors can be used for any class of amplifier. It is not limited to Class D or other switching designs. It is commonly used in the Cellular industry which was the first to take it up as an amplifier. This is because of the very fast switching speeds and power handling capability of the GaN transistor. It is excellent for operating in the Gigahertz range.

As the volume increase, production gets better, the price of the GaN transistors will come down and you should see them used ubiquitously, much like a silicon transistor today.

I don’t give out the details on my component designs, and that will hold true here also. And as noted in this thread, it matters what it sounds like, not whats in it. A Bugattis cost money and not everyone can afford one. So the best sound for what one can afford or is willing to pay is where all of us will land up.

Here are some of the early reviews and more to come from HiFi Plus, Enjoy the Music, Positive Feedback and so on.

Brutus Award , Positive-Feedback.com editor David Robinson, “After starting the listening sessions, I still didn't realize that they were Class D…at first. I really liked the initial impression that the Element 118 created in me: very fast transient response, clean, transparent, detailed, and lacking no dynamics with key recordings that I always use.
Then I walked over to the amps to assess the heat being generated, and was startled by the fact that the 118's were cool to the touch! "Damnation!" says I, "The bloody things must be Class D!"
They are, but with state-of-the-art design and execution that puts Class D into my top-o'-the-heap class of true reference amplifiers. Details will follow in my review, which I hope to have done in January or so of 2019. Stay tuned for that one…the Element 118 is serious stuff!”

You can also look up my thread on “Merrill Audio ELEMENT 118 on Tour” to see more reviews first hand. Some of the speakers used are high efficiency horn speakers. Also look for reviews by Kansas City Orchestra percussionist in other forums.

To summarize, it is not the topology that matters, it is the actual build, fit and design. The ultimate test is the listening test. Until one hears A/B comparisons and actually hears the component, it is very hard to speculate how good or bad something is by just the marketing material or chatter.

mikepowellaudio
George, isn't the Technics like $30K or something ?

Yes that's for the all out GaN SE-R1 poweramp.
Look at $4k   GaN Su-G30 network integrated amp
https://www.technics.com/us/products/grand-class-g30/network-audio-amplifier-su-g30.html

Forget continuum, it seems to be a sore spot

I'd say that's an understatement at that price for what you get inside.  
I've yet to see other models innards, as there's no pic to see of them, yet.


Cheers George