When doing GPU intensive tasks (games, rendering, 3d animation etc), there is a distinct pulsing static coming through the headphone jack AND the monitor outputs on the back of the studio 68c. Even with the unit powered off from the switch, the static comes through but not the actual audio.
I've tried unplugging it from the mains while leaving the usb connected, which eliminates the static. And vice versa, unplugging the usb but leaving mains connected, which also eliminates the static. This means it might NOT be a groundloop through mains ground, but somehow through PEN. Going through the neutral -> 5v rail on the powersupply, into the interface and back via the usb shielded ground.
The frequency of the static is in sync with the framerate of any game or scene happening on the screen, and with the GPU drawing loads of current from the psu, i think that somehow causes interferance.
But if anyone has had similar issues and managed to solve it, i'm all ears!