One more thing: besides the optical output, I've also got a headset plugged into the back panel. When speaking into the headset, I can actually hear myself through my speakers (which are connected via the problematic optical output).
So it seems that only sound playback is affected, but not the loop from microphone to optical output.
One more thing: besides the optical output, I've also got a headset plugged into the back panel. When speaking into the headset, I can actually hear myself through my speakers (which are connected via the problematic optical output).
So it seems that only sound playback is affected, but not the loop from microphone to optical output.
Any ideas?