Yes, the USB soundcard is USB powered (just a common Soundblaster SB1140). I just wanted to know if the noise is just inside the PC with ALC1220, or in USB as well.
PSU is Seasonic Ultra Titanium, rated at 850 watts and I made sure that highest power draw is around 500 wats at most, close to highest efficiency, between 40-60% of rated power.
So... i guess to get a clean reading i have to use completely different computer or device as an input.
to get a clean reading you need to use toslink out to the DAC (no electric circuit) and the DAC needs to be powered independently from the PC (external or internal PSU).
is the level of noise audible to you ?