Nathan, how would you say the CDM compares to the AK240 with iems. Some low impedance, some high.
I don't own an AK240. I am borrowing a modded AK240. I also borrowed an AK240 last week. In terms of noise levels, absolutely, the AK240 is lower, but the CDM is comparable or better than every other similarly equipped valve amp I've tried. In other words, I can enjoy it with no problem through an Ultrasone IQ.
In terms of benchmarkable audio performance, comparing solid state to valves of any kind, no matter the price, is unfair. That said, CDM is more stable within its performance bounds than is the stock AK240.
That is:
1. The CDM handles earphones with extremely wildly swinging impedances better than does the AK240. But, the difference is small enough that I don't think anyone could rightly call it audible.
2. CDM can be used in high gain at max volume with little to no ill effects. Every AK device I've tried today nerfs its output from about 90-95% of the full volume, enough that you can hear it stub the end of notes (not clipping, but a rounding or neutering of any voltage level that goes beyond that threshold).
Of course, a DAP has all the advantages of volume control and balance at low volume levels, over an outboard amp, no matter the price. But CDM is about 80% of where it needs to be to comfortably or safely use earphones no matter the sensitivity.
The rest is down to sound signature. CDM enjoys the stability of a good solid state circuit, but the warmth, and as I mentioned, cleanly, beautifully and softly gradiented transitions and textures.
If you're into valves, but not into tubey sound, CDM. If you want a very good digital experience, AK240 is pretty good. That said, if measuring the 240 against its performance/price ratio, it fails more so than does the CDM.
That's to say that ALO have done a very good job of blending performance and sound style.