New Generation Class D - AGD Audion Mkiii upgrade

I have always had a preference for horn-loaded loudspeakers which, whilst typically easy to drive, can be quite revealing (good/bad) of any changes in the system. I am running Avantgarde Duo’s and have until now always preferred valve amplifiers for their mid-range and lack of fatigue.

I have heard a number of Class D amplifiers and one or two have sounded pretty good but a bit lean compared to valves. Tha changed when I purchased a pair of AGD Audion Mkii amplifiers. The Audions have an almost valve-like mid-range but with a wonderfully transparent top end and great sound-staging. It’s always been difficult to get really convincing bass with my Avantgarde’s because if you increase the bass level the low frequencies can sound detached from the glorious mids/highs. This changed with the Audions as the bass is faster, more dynamic and just overall more satisfying.

These compact amplifiers have what appears to be a valve for each amplifier. This ‘valve’ glows red and I rather like the effect. I did think this was a bit of a gimmick at first but it contains a Gallium Nitride MOSFET power stage. However, this ‘GAN-Tube’ means that if an improvement is developed you can just swap the tubes for the new version. That is exactly what I have done as AGD have launched a Mkiii ‘GAN-Tube.

I was extremely happy with my Mkii Audions and wasn’t sure what to expect with the Mkiii tubes. But as audiophiles it’s difficult to resist an upgrade. The new tubes were fitted in under 5 minutes. I’ve found most components need time to warm-up and ‘burn-in’ so wasn’t expecting too much initially. However, it immediately became apparent that, even at very low volume, there was more detail. I pumped up the volume and was astounded by the wider soundstage which extended beyond the speakers and allowed you to pick out instruments and vocals even clearer. This is something that I’ve found difficult to achieve with Avantgarde’s and I didn’t have with my previous OTL amp. Dynamics are a strength with horns and the Audions really produce a ‘live’ sound, quite startling at times. I’m not great at describing all the audiophile things but would just say that these amps make the system sound so enjoyable and exciting to listen to. They are the best by far that I’ve had in my system.

I know some people will have a hesitation over Class D amps (like I did) but I really think this next generation amps like the AGD Audions will become more and more popular once people get the chance to hear them.



Does the ability to build a GaNFET class D of our own design from the ground up, have it meet EU Directives and get nice comments about it and such, that I somehow I am

misunderstanding the explanation and the physics of the semiconductors applied to power electronic technology and applications

seem true? Not sure where this is coming from- its not something I'd say about you in the face of similar evidence. So I have to conclude you misunderstood my post.


I don't think I misunderstood your post, you replied to our true statement about the fact we use a specific GaNFet HB device that was specifically designed and optimized for CLASS-D (Audio) applications as not true. That was already borderline offensive since your comment implied I was making up something or worse I was a liar. Nevertheless, I very gently tried to explain the reasons and the basis of my statement, and still, you ignored them and made a further simplification inherently calling me a liar or incompetent, by saying that all GaNFet as long as are "good switching devices" are good for Class-D anyway. They are not, and you can repeat that all the time you want, it will not make it right. In any case, I found this type of argumentation a total waste of time, if you wish to get a more comprehensive explanation just give us a call and I will be glad to re-explain my statement again, for the last time. 

@agdproduction The reason I responded the way I did is because your 'explanation' lacked anything that pointed to an audio application. So perhaps you could be a bit more specific. For example, having a lower gate capacitance as advantageous, but that would be a benefit to any switching device. So in order to support your position, you would need to be very specific about how the GaNFETs you use are somehow different from regular GaNFETs in a way that favors audio without favoring switching devices in general.

I had thought that was clear from my prior posts; I apologize for my lack of specificity in that regard.

Dear Ralph,

my position is supported by the quality of the sound of what we make (and what I designed from the ground-up...literally), and also those few decades spent in a much less fun environment than Hi-end audio...meaning the semiconductor sector.

Now, and with all due respect, the simple fact your last reply cites the "input capacitance", is an obvious demonstration of the gap in the fundamental know-how of semiconductors in general, and for sure in III-V material devices that exists on this matter from your side. For your benefit, you know, there are multiple FOM (figure of merit) indicators in every device that are application-specific and need to be optimized, together with the package and internal device layout, to reach the optimum performances (you can ask your friends at GaN System), and in the semiconductor industry, there are millions of dollars spent every year to gain small % edge vs. competition every year and with a new generation of parts to improve just a few of them. So it is fruitless to take this venue and continue an argument over a true statement, or transform it into a "Power Electronic 101 for dummies" type of training. Also, on the same token, and maybe I need to ask forgiveness for this ;)...well...I need to confess... I am definitely and categorically not interested in telling the "secrets" about how to make a better GaN for audio to my good competitor!  Right ?? ;)

So really, in all honestly that was not my goal, I simply wanted to re-iterate what I have said, written, and publically declared, sorry if you keep ignoring the evidence in a sort of "don't look up" style.

The results of the AGD products are the proofs and for the rest, well let's leave it as is, and let's enjoy the music again, in whichever form is reproduced :)

 Thank you and have a nice Thanksgiving!

All the best!