I recently got an HDMI monitor and tried switching to use HDMI as audio output. That worked pretty well via gnome-control–center but I noticed that some audio had a bad stereo image like one channel was delayed or with hall reverb or something odd. I started messing around with settings in alsamixer and reverting back to built-in audio in gnome-control-center.
At this point sound through the laptop speakers sounds fine but headphone output either built-in audio or via HDMI has the strange behavior.
Any ideas? Maybe I messed something up in alsamixer.