My new review for The Absolute Sound comparing AGD GAN amps with BHK300’s

If I use a switching semiconductor to switch at 2 mHz, are you going to call that device an “audio output” device???

Thats what these GaN devices are, and that’s how they’re used here! That’s how Class D amps work!  These devices are no more “audio devices” than the devices used to control industrial induction motors, or used to control motors in EVs!! Fact is, both GaN and SiC were developed for exactly these reasons: Efficient control of induction and DC motors!!!

This is a total scam to say these devices are “audio” rated, or even operate at audio frequencies!

Peoples’ lack of understanding of Class D amps makes for easy victims of false advertising!!

@wolfie62 Yes, if a switching amplifier has output devices, it really does not matter the switching frequency, they are indeed output devices as the power that the amp makes is developed by those transistors.

Now you can use any transistor to do the switching, back in the 1960s it was done by silicon transistors. Over time that has evolved and the switching frequencies are much higher as well. In a switching device that is more useful for a class D application, there are several helpful parameters beyond those that might be used to control motors and the like. A low output capacitance comes to mind. That's something that is useful for a class D but not particularly for other switching applications. That was one of the things we looked at when we chose the output devices for our class D amp. But the devices we use were not marketed as 'audio output' nor do we say that they are meant for that.

Another, much simpler way of knowing that they are indeed 'audio output devices' (as you put it), is to run a class D amp into a speaker and listen to it- you can hear that it passes a signal. With the 'audio output devices' removed it will not do that. Walks like an 'audio output device', quacks like an 'audio output device', its an 'audio output device' albeit one used in a way that isn't like that of an A or AB amp, in much the same way that traditional A or AB solid state amps have used output semiconductors that were not designed with audio in mind.

To my knowledge only one company anywhere has made the claim that the devices they use are 'audio rated' as you put it (although I am not sure they used those words, so paraphrasing). The only parameter that might make that so is the low output capacitance I mentioned. Beyond that, yes, the output transistors of any class D amps are designed for switching with power.

Miroslav Tadic and Yvette Holzwarth - "Luka"

The virtuosity of the "Luka" album has become one of my favorites for exercising the GanFets and showing what they can do. They do stringed instruments very well indeed. Quobuz has it.

@emailists Great review, I for one quite enjoyed reading it and would encourage you to take on more in the future. Don't WORRY about any NAYSAYERS and their WEIRD way of COMPLAINING!!!!

A question for any AGD Audion owners hanging around - have any of you had experience with the earlier iterations of the output stage "tubes?" I am curious about how they sounded compared to the current "mk3's."

@atmasphere

To my knowledge only one company anywhere has made the claim that the devices they use are ’audio rated’ as you put it (although I am not sure they used those words, so paraphrasing). The only parameter that might make that so is the low output capacitance I mentioned. Beyond that, yes, the output transistors of any class D amps are designed for switching with power.

A loudspeaker is a motor. Also a transducer.

Output capacitance is really not a “thing” for class D amps, other than internal capacitance (parasitic) can effect the maximum switching frequency and possibly efficiency of the switching device, how much of the switched energy is converted to heat. That’s the only advantage of GaN devices; higher voltage, less heat, higher switching frequencies. It has nothing to do with transfer of energy to transducers (loudspeakers).

Im not a “naysayer”. I’m just a “factsayer”. I strongly dislike those manufacturers or reviewers who use consumers’ ignorance of technology to sell stuff.  These “proprietary” GaN “audio grade”devices grabbed and used for their singular audio use/purity is a “snake oil” claim. Pure and simple.