I'll do my best to explain how the sound changed: toggle "mono" mode in Windows while playing a track...the music loses a sense of depth, dynamics and space. The change I was hearing was similar to that (not 100% mono, but moving in that direction). For a given volume, I was also missing a sense of impact and detail; the notes were all there, but the original sound was more visceral, and whatever hardware/software issue I was having muted this. I verified that all of the Windows sound settings were identical (at first I even thought I had "mono" mode on accidentally, but that wasn't it).