I.E. the amp is set to modern (highest gain mode) and the gain knob is almost maxed and the volume is on like 3/4 before it is even audiable on any channel. every channel is very quiet, but channel 1 is quietest, channel 2 is in the middle, and channel 3 is loudest. all channels have no distortion (due to the lack of gain) and are rediculously quiet. what would cause this