This problem's a bit more puzzling than frustrating. I have two pairs of headphones, a Denon and a Bose, both of which play a stereo input from anything other than the DSL in stereo. Now, my DSL outputs in stereo via the built-in speakers, and in stereo via the Bose headphones, but only in mono via the Denons. Why is the relationship between the DSL and Denon headphones so special? EDIT: The Denons work through a splitter. Is it something to do with the jack?