I bought the SMSL sApII as a stop-gap after my Little Dot MKIII failed after 5 years of use, five hours a day. No complaints there! I just don't have the money to upgrade just now! I have invested in some great tubes for the LD MKIII and, plan to buy another one as soon as possible. So, in the meantime I'm using the sApII with it's supplied PSU. My front end is a PC running JRiver Media Center 21 playing FLAC files via WASAPI to a Musical Fidelity V-LINK to a V-DAC via SPDIF optical. The V-DAC is battery powered. Headphones are unmodified...