I just purchased a used BC Rich American mockingbird bass, signed on the backside of the headstock. Good price but pretty well beat up. Pictures later. Controls are my concern. I have no knowledge or experience with this bass manufacturer. Not sure of what controls are designed to do. I have played around tonight trying to familiarize. I think one or more pot is having issues. What I have noticed is when playing E A strings, sound booms. But when playing D G stings, the sound is very thin. I have tried all combination of control settings. Something seems off to me. I have searched for wiring diagrams for this particular bass model but all I get for results is Mockingbird guitar wiring diagrams. No bass. I would appreciate any advice regarding where I might find a wiring diagram specific to this bass.