Topic: Problems with Fireface 800 outlet

During a gig tonight i got problems with output 9/10 on my Fireface 800 which leads processed guitar sounds from max and ableton into my amp. The signal was so low that i had to use another output, and there was a weird crackling noise inside the Fireface itself when i turned it of.
Have anyone had this problem? Is this something i can fix on my own?