The USB appears to be for output from the computer only.

I just checked the "Sounds and Audio Devices" in Control Panel. The default UAC3553B USB-DAC (the RR2150 as seen by the PC) offered settings for playback only, whereas the internal sound card offered options for recording as well.

I wonder what format it the USB-DAC decodes, since it is dependent on having a player on the PC to decode the original file, whether it is cd-audio, wav, wma, flac, shn, mp3, etc.