Nice objective review and better than typical TAS reviews because you deftly compare two excellent amps and articulately explain critical differences, which really provides a useful relative perspective on each amp rather than just extolling the virtues of one amp in a vacuum. The result, and which I am sadly and very rarely able to say about any other TAS review, is that I came away with a good understanding of what each amp actually sounds like and which one I’d like to explore further. Maybe someday TAS will grow a pair and produce more useful reviews like this, but I’m not holding my breath. Nice job.
My new review for The Absolute Sound comparing AGD GAN amps with BHK300’s
I am normally best suited to be behind the camera, but The Absolute Sound convinced me I should try my hand at reviewing. In listening to AGD’s Audion GAN amps I compared them with my BHK300’s. This was done direct from the my Dac - PS Audio DS MKII with APS transformers, to eliminate any preamp interactions.
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So much WRONG here! Comparing a Class D to an analog discrete amp, for one! Class D has far fewer parts and switching style supply. And that load of crap about “unobtainium” audio GaN MOSFETS!!! Gees Louis!!! Switching MOSFETS have been used in high dollar audio amps for DECADES!! GaN MOSFETS are still MOSFETS!! Most are very linear but the GaN have efficient on/off states. GaN have efficiencies for switching use at ULTRA-AUDIO FREQUENCIES, hence THE CLASS D amplifier!!! DUH!!! So this is supposedly an “AUDIO GaN MOSFET”…….. used as a switching device in a CLASS D audio amp!!! You HAVE GOT to be kidding me!!!! The GaN devices aren’t even used in AUDIO FREQUENCIES!! In a Class D amp, they are used as very high frequency switching devices, and NEVER SEE any frequencies between 20-20kHz!!! And then, the CUTE little mounting of the switching circuit inside a glass envelope!!! Oh for Pete’s sake!!! REALLY????!! Sorry!!! But this review is loaded with disinformation and downright misleading claims by the manufacturer, glossed over and passed on to gullible consumers!! REALLY????!!
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Whatever corrections or disagreements you want to make with the author would be much more effective if stated without all caps, extra exclamation points, and snark. This hobby is full of enough drama without unprovoked hysteria. Take a chill pill, bro. |
@wolfie62 Not really sure what you’re saying. GaN FETs are clearly different from MOSFETs, and the performance advantages of the former have allowed amp designers to not only more seriously rival traditional amps but are now starting to surpass them. When a company like Atmasphere makes a GaN amp that the designer in most ways prefers to his MUCH pricier OTL tube amps that’s pretty strong evidence that something significant has changed. Again, not really sure what your point is here. |
@wolfie62 Its perfectly valid to compare amps of different classes of operation. Regarding the 'unobtanium' GaNFET, I understand your skepticism- I reacted the same way. The designer claims he uses a device 'designed for audio'. As you know, GaNFET's main advantage, their raison d'etre, is for switching so of course any GaNFET could be used but if you wanted to optimize one for a class D audio amplifier it would have a low output capacitance. That was something we considered when we chose the parts we use as well. So we can assume that is what is being used. That is the extent of being 'designed for audio'.
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@wolfie62 Wrote:
I agree! LOL 😎 Mike |
I’ve heard the AGD and they sounded good. Are they worth the premium price compared to the competition? Have not directly compared so don’t know but having heard many Class Ds including several I own currently, I’d say anything is possible. Making the circuit look like a vacuum tube is a nice touch both from an aesthetics perspective and surely helps up the appeal to those attached to vacuum tubes that might otherwise be less likely to move on, so an adept marketing move there for sure. Vacuum tubes fascinated me as a child and still do. They are all glowy and I still think they are way cool looking in a 1950’s sci-fi kind of way
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This is hilarious, actually!! 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!! |
See my post above. That’s my point! |
@emailists Great review…. I saw it on YouTube a few days ago. I like your style of review. You should do more! @bolong I concur with your assessment of how different interconnects and power cables modify the sound of the Audion amps. The Audions seem to deliver whatever sound qualities a cable or component feeds it. They are nice amps in my setup. |
A really well balanced and useful review - thanks. I bought Mkii Audions and have upgraded to the Mkiii ‘tubes. These amps are so transparent that changes to interconnect cables or anything else in the system will clearly be audible as @bolong describes above. I’ve had Class A, AB solid state along with SET and OTL tubes amps. I don’t really care what amp configuration I use if they sound great! |
@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 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. |
@wolfie62 Output capacitance of a class D isn't a thing as you say, but output capacitance of the output devices is. Its nice to have that low for better switching.
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Exactly what I already said. And “low output capacitance for better switching” is exactly my point!! Those output devices never see audio frequencies!! They are switching at much higher frequencies than the audio spectrum!! So finally we are in agreement. The GaN devices are switchers and are NOT audio devices. |
