I am having an issue with my GK MB115 combo and was wondering if any of the tech gurus might be able to offer assistance. I'm getting distortion out of the speaker and the headphones no matter what the volume, tone, or boost controls are set at. Also, the distortion happens if I plug in my i-Pad through the AUX port or use any of my basses through either the active or passive inputs. The distortion is worse for the low notes than for the higher notes. My fan is working and the issue happens as soon as I play the first note, so I don't think it's a heat related problem. I've attached an image of the schematic. Any help would be appreciated.