Thanks. The Zen Stream I use for my signal source allegedly has ANC and noise isolation built into its USB output, and I feed it into a Topping D90se. My system is dead-quiet to me, although I lack any measurement instruments to verify objectively.
I’m not sure what Rob Watt’s motive is in raising this topic in his latest unsolicited lecture on Head-Fi, but many folks are slavishly expressing their gratitude to him for illuminating this insight. Some seem to be rushing to yank out their USB connections in favor of TOSLINK connections, and I just don’t get the need—I have many music sources with sampling frequencies above which TOSLINK can handle, and they sound terrific to me through USB. :/