I have normal stereo headphones which work fine On a specific PC running Windows 7 the external speaker and USB speakers work fine too But when I plug in the headphones, all I hear is muffled music, no voice track? It sounds like it is being split into 5.1, and I am getting just the L & R components, and not the centre voice channel? In the Playback devices (sound) control panel, I can adjust stereo or 5.1 for external speakers or USB speakers, but not for the headphones. The config button is grey out for them Is this the problem, if so how do I fix it?