I mean because you asked, even though it's not really relevant to what you're looking for... I'm currently nearing what might (pfft who am I kidding) be the end of a multi-year side project to build a small integrated USB powered UAC2 DAC+HPA with reasonably low jitter clocks. The UAC2 part has been fairly non-trivial, no off-the-shelf solutions are available, and I don't have the low-level USB chops (or the time) to implement it myself from scratch. XMOS is the only vendor I'm aware of with reference code available, but their chips are 'weird', expensive, and have thermal pads that *must* be soldered. After quite a lot of difficulty soldering the package properly with an iron, and a few weeks futzing around with the development environment and porting the reference code to my hardware, I have got an XMOS-based solution up and running quite well with dedicated 44.1K and 48K clocks, supporting 24b/192KHz. It mates with a CS4398 DAC, using OPA1656 for filtering and as a headphone amp stage, running at +/-9V. It all fits in a Hammond 1455C801 case. I think it probably blows the USB 500mA budget a bit but seems to work fine. It does indeed get hot, and I don't know enough about the XMOS microcontroller to know if a ton of stuff could be turned off to save some power, it's a pretty power hungry micro. Sounds great, though
. I'm mostly driving relatively low impedance DT770 Pro 80's with it.
Future direction for this is to try and design a slightly less densely packed 'desktop' DAC with less DC-DC, a separate 2-channel DAC for speaker output, and an ADC input.
The
O2 Headphone Amp is a good design to investigate if you're considering going down the DIY road yourself. Very objective design, design decisions are well discussed and justified. Same guy released a UAC1 DAC back in 2012, but it relied on a proprietary USB interface chip. It's too bad the guy disappeared, because his blog had some great measurements / reviews of popular 'low end audiophile' equipment.