Emu XL-7 & MP-7 User's Group

hi,

this is most likely going to be a dumb question for most of you... i 
am using my xl-7 as a sound module for live performance.  when i play 
the pads (or a midi keyboard for that matter) the sounds lose the 
high end at random.  one minute they will be nice and bright, and the 
next they will sound muffled and dull.  am i doing something wrong? 
any and all help will be greatly appreciated!!!

thanks,

ryan