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.


I just placed an order for the new AGD Duet monos and Andante pre-amp.  I have been wanting to explore Class D for many years but hesitated because of the criticisms of the sound quality and also the feeling that Class D was still rapidly evolving.  What finally convinced me was Ralph's conclusion that his Atmasphere Class D amps were as good as his OTL tube amps, and then the outstanding reviews and the technology used in the AGD amps.  

I'll be comparing this to the Boulder 866, using a Playback Designs MPS-8 CDP/DAC and SF Electa Amator III and YG Hailey 2.2 speakers. I had been planning to wait on trying Class D until Ralph developed an integrated amp, and I still l want to compare this to the Atmasphere Class D amps and hope to do this in the future.   I need to work on my critical analysis tools so that I can say something more than "this sounds really good", and "that sounds really good too".  I'll post again if I have anything useful to say.




An 8 page Six Moons review?  Nice. 


Let me pop a few Advil up front so I can be properly medicated in order to be able to make it through and  soak it all in and I'll see you all on the other side. :^)

This Audion GD is just a Class D circuit stuffed into a KT88 glass envelope. It has zero relation to a real vacuum tube. A clever marketing ploy! 

@jasonbourne71 No, it’s absolutely not just a “clever marketing ploy.”  It’s designed that way so that when upgrades come, and one already has, the user can easily just swap the new circuit in.  That it looks cool too is just a bonus.  

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