Hi all! At band practice today my amps suddenly started to "fart". My amp is a Yorkville 400B. It´s a 400W amp with a 15" Celestion speaker. I turned down both gain and volume to 1 and tried to play but it still farted. It was very noticable on the E and A string. I´ve got an active bass but I put in a new battery just a couple of weeks ago so that shouldn´t be the problem. After much fiddling about it suddenly stopped and seemed to do fine for the rest of the practice. I have usually got the gain at 5(from 1-10) and the volume on 2. Is this something I should be worried about? I´ve got an important gig coming up next friday and three other bands will be using my amp. Any opinions?