I don't think that most dac's even the most expensive one have galvanic isolation, so sometimes ground loop is an issue.
The think i don't know is why some studio monitors have this issue and others not, i mean picking up interference from ground.
I know that i can stick to monitors that don't have this issues, but then again why this problem is bigger when a high end pc is at heavy load ?
Anyone has a diagram of usb signal when a pc with high end graphic card is at heavy load, how much noise it has ?