Hello all!
I am a longtime lurker and longtime fan of AVA. I've been lucky enough to have the M225, DVA SET 600, and now the M750 in my listening room over the years. All three of these monoblocks bested nearly all the brands I've compared them to and it was very interesting to compare them to one another. There have been extensive writeups on the M225, SET 600, and M750 but not a lot of comparisons. Here is my personal experience.
Analog Signal
Fern & Roby Heirloom Turntable w/Sculpture A3P Cartridge -> Modwright 9.0x Phono Pre -> Ayre KX-5 Twenty Preamp -> M225/SET600/M750 -> Sonus Faber Maxima Amator
Digital Signal
SotM Ultra Neo -> TXUSB Ultra -> Holo May Kitsune -> Ayre KX-5 Twenty -> M225/SET600/M750 -> Sonus Faber Maxima Amator
All of the typical impressions (Soundstage, dynamics, tone) apply to all three of these amplifiers. As far as the differences I heard they were subtle, but noticeable in my setup.
Between the M225 and SET600 I found the SET600 more effortless, especially in the low end. It has a warmth in the midrange that makes for a more relaxed presentation. The M225s are slightly more forward. Not bright, but more forward than the SET600. Because if this, they are sightly more detailed but the tradeoff of a less lush midrange/less relaxed presentation. Soundstage, imaging, etc were pretty even. Personally, I liked the SET600 in my setup more than the M225. I found the tradeoff of the warmth/relaxing presention vs the forwardness/detail of the M225 to swing in favor of the SET600. I found the tone of the SET600 to be slightly less accurate but more engaging and made my brain turn off and listen. Depending on the pairing/preference I could see either one "winning".
For the M750 vs SET600 - the M750 are more similar to the M225 in their voice. They have more detail than the SET600 and slightly more detail to the M225. The difference between the M225 and M750 is how they present that detail in space. The M750 have slightly larger (wider/deeper) sound stage and transparent imaging than both SET600 and M225. The M750 adds more transparency in the upper end which leads to better imaging and more realistic presentation. The openness of the M750s alsos allow the midrange to come through more. This was the main difference between the M750 and M225 in my mind. The spaciousness allowed the midrange to come through more (or maybe it was the increase in power?) And the tradeoff of the M600 warmth and the detail/spaciousness now swung in favor of the M750.
If I could tweak them a bit, I would bring just a touch of the M600 warmth/magic (like 10-20%) into the M750 and that would be my perfect amp.
So in my setup, I've decided to keep the M750. I'd rank them.
M750 > SET600 > M225
Hope this is helpful to any folks out there looking at these. For anyone curious, my SET600 are available and still under warranty until Jan 2025. 3995 to your door!