hi people, sorry if this is in the wrong place just its for a pre amp part.....sort of. ok so i have a 3 band seymore duncan pre amp (stack bass treble, mid, pan and master) i fitted it ok it works fine but the mid control knob keeps falling off . i have tried tightening the screw as tight as i can but as soon as i move the knob off it comes. seems like the screw just slips off the flat part of the shaft (for those that dont know the pots have a half shaft, like a half circle so the screw can tighten to the flat of the solid shaft) can you get replacment knobs? maybe like jazz bass ones but with the concentric pot? id prefer to use what i have but if i have to ill get new knobs. cheers.