One major drawback is the device but and is probably due to the system, the WD TV Live Hub namely shows the same mistake: The stereo output is booming and is not to be used. There is no ground loop, no the device itself generates the hum of the other tones superimposed.
Property me then an "audio digital to analog converter" (Link: PSC = 1) increased and thus uses the optical output. Works flawlessly and is of good quality. Despite a star deduction for the unusable audio output.