Or is it just ProTools 5.0? Here's what I read on the Digi site: I'm wondering if it's not just a ProTools problem, since my mixes don't seem that dull when switched to mono! [using Logic, of course] "I've spoken to Digidesign and they have said that there is a one sample delay between the left and right output which causes this problem. To see for yourself, record a mono sample and then spot a copy of it to another track. Pan the two hard left and right. Switch between Mono and Stereo and you'll hear the effect. Grab the left side and nudge it by one sample with the plus (+) sign on your numeric pad. It will be mono compatible then. Undo using (command-Z) and nudge it by one sample with the minus (-) sign on your numeric pad and it gets worse."