This may be a matter of adjusting the plug right, as the standard A/V Output jack consists of three channels (audio left, audio right, and video). On my camcorder, it seems that when I plug-in headphones and pull the plug back a certain amount, I am able to hear both left and right audio channels with no added hiss or buzz. If the same goes with your camcorder, it may simply be a matter of finding the sweetspot.
