2 days ago the mid on my basses on board preamp started making weird noises and sounded really scratchey and buzzing. so i switched it to the 2 band option, and it was doing the same thing last night for a show. I hadn't expected a change. Then i clicked it into 3 band mode and... nothing. it was fine. perfect no noise. no buzz or hum. It was weird. what could it be, and should i be concerned and get it fixed?