my Ampeg rocket bass 100 has started to distort at times. Usually on lower notes but sometimes on all notes. It's almost a fizzy sound with some speaker crackling sounds. Doesn't happen all the time but it's getting more frequent. I'm sure I'm not clipping the preamp. I sprayed contact cleaner in all the inputs. Took off the back and checked all the "plug in wires". I think it may be something with the line out or headphone jack. I ran a cord in and out off the inputs and at one point it killed the sound. I then continued to plug and unplug the cord repeatedly and the sound came back on. Any one else have this problem with their Ampeg rocket bass amp? It is an American made not the import if that makes a difference.