The Oppo BDP 105 can be used as a stand alone DAC It has the Square USB Connector (Type B) and a windows Driver. I am already using JRiver to play 2ch flac through it with no problems. I would like to use JRiver to play multi-channel files so I can have gapless playback. The Oppo also has standard USB inputs for mass storage, but will not do gappless playback.
Ahh, I see. That's nice (not shocking, Oppo makes nice stuff).
You'd have to check the specs on the Oppo to see if it is supposed to support multichannel input that way. It could be that they only implemented it internally and not in "DAC mode". Or, perhaps it does support them, but doesn't support them at the same quality settings (maybe in multichannel mode the best it can manage is something more like 24-bit 44.1/48kHz).
However, to be clear: MC handles multichannel FLACs just fine (I have a bunch). I'm not sure about WAV, but I'd guess that it shouldn't be a problem.
To enable multichannel output in MC, you simply select your audio device via Options > Audio (or make sure it is set as the Windows default). Then, set the DSP > Output Format to the proper number of output channels. You should be able to test if it is a bit depth or sample rate limitation by starting low and then raising them up from there until it complains.
I did see this note on the
AVSForum Owners thread:
SABRE32 Reference Audio DAC - The DAC is one of the most important components for digital audio playback. The SABRE32 Reference ES9018 from ESS Technology is the world’s best performing 32-bit audio DAC solution targeted for high-end consumer applications and professional studio equipment. With the ESS patented 32-bit Hyperstream™ DAC architecture and Time Domain Jitter Eliminator, the SABRE32 Reference DAC delivers an unprecedented DNR (Dynamic Range) of up to 135dB and THD+N (Total Harmonic Distortion plus Noise) of -120dB, the industry’s highest performance level that will satisfy even the most demanding audio enthusiast. The BDP-105 uses two ES9018 DAC chips - one for the 7.1-channel output, and another for the dedicated stereo output. To learn more about the technologies behind the exceptional performance of the SABRE DAC, please read the SABRE Technical White Paper.
So, I'd guess from a start that your bit depth might be too high, assuming it does let you access that second 7.1 configured DAC via the USB.
If the DSP > Output Format > Bit Depth isn't set explicitly (it is set to Source Bit Depth), try setting it to 32-bit (which is what the DAC is internally anyway), and see what happens.