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.


...and I'd bet they can't warm up a the gud 'ol daze.....😏

"And, if one misses the weight of the old mono's, you can put them into a 'spoof chassis' of lead....."

(Just teasin....🤷‍♂️ ;)...)


Hi there @ghdprentice  In my system I didn’t find the Mkii Audions to lack a bit of refinement on the top end but I would say that the Mkiii GaNTubes have opened up the top end quite significantly. Last night I was listening to Talking Heads ‘Little Creatures’ on vinyl - it’s a great recording and the drums/cymbals were the most life-like I’ve heard from my system.

I had a look at the AGD website and the designer (Alberto Guerra) outlines the design improvements he has incorporated into the Mkiii tubes. I don’t understand it all but this gives a bit of insight: 

“With the new MKIII, we have extended the frequency response of the power stage, now flat up to 60KHz, and by a combination of layout improvement and the re-engineering of the output filter, we managed to also significantly increase the slew rates performances.”


There are many way less costly options and are too expensive for people not into high end audio (99%?) , but having heard them they sound very good and are likely to retain a niche in teh high end world for the foreseeable future. Plus the modular tube like aesthetic on the top models (despite not actually being a vaccum tibe) will appeal to tube lovers that otherwise might hesitate to leave tube amps behind, and may provide a good path for upgrades moving forward I would expect.

Don’t know about appealing to tube lovers.  Based on comments I’ve read many seem to be offended.  Personally I’ve used tubes for over 50 yrs and I think the Audion’s look pretty cool.

Myself, I grew up in the 60’s and helped customers with tube replacement working in various electronics stores back in the olden days when tube testers were still a common sight even in some drug stores.  So I have a nostalgic soft spot for tubes. THese days I am a long time  career tech guy and have come to the realization that vacuum tubes are still way cool looking and all glowey and stuff and often sound very good, but practically their time has come and gone. My reference system is 100% tubeless these days (yay!).

But I still have that nostalgic soft spot in my heart for tubes and the AGD design does float my boat by adapting a vacuum tube like aesthetic but putting much better 21st century amp technology in there. The best of both worlds for me but still only for a premium cost....