I use HDMI which transfers video/audio to my TV which then forwards the audio to the Receiver. The optical out jack also functions as Mic so I cannot really do like you suggested. How does one spot the ground noise? It's been a while since I tested my onboard audio but I didn't hear anything in particular back then. What density patch was that? 2.0? I wasn't aware of this. I assume you mean stuttering and not FPS drops? If you mean stuttering and you use in-game Vsync plus has a nVidia card then you're out of luck until Blizzard patches the game.