The USB input on the DLIII is the weak link. I used a USB?SPDIF converter with the one I owned.
Agreed. Now, with everything tidy, surely the SBT + S/PDIF + DAC configuration excels with mastery.
When there was the problem with the amp AC line, the SBT/coax sounded lean and with over-tight and hidden bass. In a way, the USB input seemed to come out better (less worse), although it was not good either.