So it's out here in China. I've had one for a few days, been burning it in and getting used to it over the weekend:
I've owned the M12 (twice) and M15 previously, although unfortunately don't have either anymore for direct comparisons.
To start I should probably say that although I've never heard Questyle's desktop products or DAPs, from the M12 and M15 my impression is that their house sound is kind of 'studio' with a touch of added soul or emotion. Generally accurate and on-point, but not analytical or boring. Also to my ears what I hear from their current amplification is very good extension in both the bass and treble, and an interesting sense of dynamics - not just in terms of big swings of volume, but the relative volume of each instrument just comes across as more fluid and continuous, somehow, than many other sources.
So I'm hearing all those same traits with CMA18p. The bass is not only deep but nuanced too. In one test track I use a lot (Rivers of Nihil 'Terrestria III' anyone?) you can hear little nuances like the wavering tail end to the synth bass notes, very tasty indeed. At the other end of the spectrum the treble is detailed but not harsh.
I remember the M15 as having a more left-right presentation than the CMA18p - the new model feels like it has a more rounded soundstage with added dimensionality.
The M12 and M15 both had ESS DAC chips, so the CMA18p is the first Questyle device I've heard with an AKM chip. I feel in general that too much is made of the DAC chip in this hobby - as a lot can change with implementation - but it seems that most people do hear some sonic differences between manufacturers. I'd usually associate AKM's "Velvet sound" as having a little warmth in the bass and a sound that's clear without being harsh - not necessarily 'smooth' but perhaps heading in that direction depending on tuning choices by the engineers.
With the CMA18p I feel those traits are present. There is perhaps a little extra body to the bass, but more in the sense of a touch more sustain and longer decay, lending the bass registers more presence in the mix, rather than there being more bass quantity-wise per se. The leading edge of bass notes is maybe rounded off just a touch too - in a good way, in the sense that I can put on something with flat-out double bass drumming or similar and the speed is there, but with a natural sense of attack that never gets too much. I felt the same way with the M15 too. In contrast, whenever I've heard a THX-based source I've often found that they can do speed and accuracy but passages like these can get fatiguing, as the way they render rapid-fire staccato on-off notes gets to a bit too much after a while.
All the above impressions are with the single-ended output by the way. The only headphones I have at hand are the B&W P7s (high sensitivity, low impedance dynamics, wired for single-ended use only). I'm somewhere in the 75% volume range on low gain.
Function-wise one thing I've discovered - it's mentioned in the manual too (see below) - is that you can't charge and play at the same time! I left it running on Friday night connected to my computer to clock up some burn in overnight, only to find it was flat in the morning - then looked up the instruction and realized it doesn't charge while playing. I think this will be the biggest practical issue in long-term use. So far I'm not sure if it has an auto-off feature either - just yesterday I found it out of battery after being interrupted, unplugging my phone, and leaving it sitting on the desk while I dealt with something else. Seems like you need to remember to switch it off after use, and also plug it in to recharge so it's ready to go next time.
If there's anything that might be weird function-wise it would be the volume display - the percentage LEDs indicate battery light when charging, but volume level during playback (and I think you can tap power to get them to show the battery level). The LEDs show 25% jumps in volume, and then within each 'band' there's 8 steps before the next LED goes on/off, giving 32 steps in volume in total. I find the jumps between are a bit big and I'm juggling between the volume slider on my phone and the CMA18p volume steps to dial in the right volume.
So the volume indication is a bit of an unusual decision, and it seems like it would be more intuitive to just have different indicators for volume and battery level, but I suppose that would add more battery drain with more LEDs. Still, a natural competitor would be the Mojo1/2, and that has it's own design quirks with a steeper learning curve than CMA18p so it's not that bad (and I say that as a Mojo-lover too!).
In regular use the CMA18p does get a little warm, but nothing like Mojo levels of heat.
All I all so far I feel like it successfully bridges the gap between dongle and desktop sound quality. I've only used the USB input so far, haven't tested the Bluetooth or analogue inputs. I hope that either Questyle or a third party like Dignis make a case for it in the future - it seems too nice to just through in my pocket on the go.