I'm still have some strange issues using Line Out.
When I connect the DX80 to my hifi, and choose the input selector on my preamp, for a second I get full output (1.2vrms? I remember reading it's not 2v?) but then it drops way down.
It might be the relay doing something? Especially if it is only outputting 1.2v maybe that is why the sound is so low on my rig (which uses an LDR pre).
Did you hear some hiccups or the song paused for 1-2 second while using line out?