The McIntosh USB DACs prior to the newer units with the DA2 and possibly the DA1 (although I haven’t tested the DA1) were basically unusable with USB since they would auto mute when there was no signal and would take a second to unmute meaning you often missed the first second of the first song or every song if you don’t have gapless playback.

Also the D100 was especially annoying since it had a relay that would click every time it muted and unmuted. All the DACs work fine with optical or coax but I wouldn’t recommend anything other than the DA2 if you want to use USB.