I suppose it’s possible the USB input needed more burn in, since it hasn’t been used at all prior to the comparison.
Seems like a great setup! Was just curious. Since I use my PC as the source I usually have the XMOS driver, Foobar, and Jplay to fiddle with settings. Each has adjustable buffer and bit rate levels, Jplay with even more settings. I have gotten used to using them over the years for these evaluations to eke out extra performance from even the cheapest dacs. But I think moving forward I'll use a more standard source like a cd player or even a basic Allo w/coax.