My laptop is an HP 635 A1E29EA. As far as I could fathom, there is onboard audio only, no dedicated sound card. I recently bought the Sony MDR-V6, and am very happy with them - however, when they're plugged in there is a slight background hissing noise both when there is no audio playing and when some is (I can hear it during the quiet parts of tracks in the latter case). Unfortunately, I have no speakers to connect the headphones through (instead of straight to the audio output jack), so I can't know whether doing that would help, but I have a feeling it wouldn't (forgive my ignorance here). I've heard that a DAC may solve my problem, as well as improve the sound quality by a small bit. Is this true - should I be looking at getting one? Thanks in advance for your advice!