So can anyone who has used the UR824 advise how its sound quality stacks up against dedicated two channel DACs for music - resolution, dynamics, musicality, imaging etc? Any reference points in terms of specific models or general price point equivalency in the 2 channel DAC market?
To me it sounds significantly better/clearer than my Fiio e17, and about the same as my ODAC. Which makes sense; both the ODAC and the Steinberg are very low noise, and you'd expect DACs to start to sound more and more similar as they introduce less and less noise and distortion. I haven't had much opportunity to interact with high-priced two-channel DACs, so I can't speak to the comaprison.
But the Steinberg has got a 117dB dynamic range on the line outputs, and a THD+N of 0.0009% http://www.steinberg.net/fileadmin/files/PRODUCTS/Audio_interfaces/UR_Series/UR824/Downloads/UR824_Technical_specifications.pdf. That's not at the bleeding edge, but still extremely good, and I haven't seen many 2 channel DACs in a comparable price range with noticeably better specs.
For reference, the lowest noise DACs I've seen currently in production have around a 128 dB SNR. Bruno Putzeys forthcoming DAC is currently testing with a 140dB dynamic range in the prototype (which would be the lowest on record), but that's a prototype, and it'll cost more than 10K when it debuts.
Personally, the noise floor in my room (and the noise floor on my amps for that matter) is much higher than the noise floor on the Steinberg, so as far as I'm concerned it's perfect
Secondly, I understand the UR824's optical outs each allow an external (and potentially higher quality) 2 channel DAC to be connected via S/PDIF and that theoretically at least the UR824 passes clocking information over S/PDIF to the external DACs. Has anyone tried this in practice with a 2 channel DAC from a different manufacturer - do the UR824's internal DACs and the external DAC stay in sync?
To my knowledge, all SPDIF signals carry the clock. I've successfully used the SPDIF out on the Steinberg to sync a Fiio e17 to the Steinberg and it worked a treat. I don't know how it will work with any given DAC, but I'd expect that any DAC with an SPDIF input would sync correctly.