My pair of ipod headphones which I use in my pc suddenly produces an imbalance in sound. Sound is still coming out of the left side, but it is noticeably less loud. If I try to shift the volume balance, that results in balanced but extremely weak sound, as in I have to crank it up to the top to get decent sound. This is the third pair of earphones that this has happened to. I know the problem is in the earphones because the problem is the same even if I try them elsewhere.