Hi Jon2020, yes agreed - I think SPDIF is likely better than USB, or at least I'm very happy with it.
My only reason for needing the USB input to work is that it is required for me to take advantage of a separate DAC within my DAC - a DSD module that allows me to play DSD files, and from what I've read that experience takes the DAC to a new level and is one of the key benefits/features of my DAC. You can read a bit more about DSD at the Lampizator website. USB is the only input that supports DSD files with this DAC.
My only reason for needing the USB input to work is that it is required for me to take advantage of a separate DAC within my DAC - a DSD module that allows me to play DSD files, and from what I've read that experience takes the DAC to a new level and is one of the key benefits/features of my DAC. You can read a bit more about DSD at the Lampizator website. USB is the only input that supports DSD files with this DAC.