Heck, I don't even see how you control this thing. It doesn't appear to come with a mixing console. There's a "control panel" but all that's for is showing you whether it's in USB 1 or USB 2.0, and allows you to select the alternate set of ASIO channels for the headphoens (3/4). How do I route sound and select the line ins to do a Rightmark test with it? I managed to get some of dropouts reduced or completely eliminated by disabling a bunch of stuff and getting dcp latency down somewhat. But Mixcraft is still wrecking havoc whenever I play anything with it.
Edit: While there's no ASIO routing, you can use the Windows routing system for RMAA. Channel balance is pretty dodgy on it below 9 o'clock and in most places it's a little higher than it should be. My unit is imbalanced to the left by 0.2 full scale, the bass rolls off on that channel, and the phasing in the low end on the inputs is indeed inferior to the 1212m.
The headphone amp itself tests pretty good without a load. I need to get some stuff to load it if want to test it for that, but the necessary odds and ends are in storage. I can tell by ear that it doesn't like driving loads below 70-80ohms really loud past 2 o'clock, but seems fine when driving over 100ohms at any volume. I suspect the headphone amp has no exaggerated attack if I feed it square waves. Usually an afterthought jack will sound hard or exaggerated in attack or both. This one seems to do none of that to my ear. And while macro dynamics aren't great into low impedance on it, the microdynamics sound pretty good and it's very easy to pick out volume changes. Dynamics are fine at higher ohms and it should be completely damped & kosher for anything over 150ohms if you can get it loud enough for a particular can. It's too bad they didn't make it a zero ohm output, but if it just had a better pot on it it'd be a nice (though voltage-limited) jack for HD650s or the big Beyerdynamics.
Just did some TrueRTA tests. There's no way to tell whether it's the line/dac stage (prior to the headphone jack) or the inputs without a second soundcard input, but the squares do seem a bit slow in the rise and there's a touch of leading and trailing edge exaggeration. There's some jaggies along the top, too. I have to assume this is the input stage doing this. Because, while I can maybe buy the slow part (the headphone jack does sound relaxed), I have a hard time believing the line out stage is producing the exaggerated edges. The fact this is all present on both the line out and the headphone jack tells me it's either the line out stage or the input stage. So the jack itself is definitely not adding to the slow rise or the jaggies. My guess is it's all the line inputs, which would mean, other than the limited max voltage and the 22ohm impedance, the class A headphone amp is not a terrible one.