hi guys i bought a mid 80's (i think it was made then) carvin LB75 about 5 years ago and i have a question that i'm really ashamed to ask. there are 4 knobs on my bass, one is the volume, one is the pickups and the other two i have no idea what they are. i am pretty lame when it comes to this sort of stuff so any help would be appreciated. i'd like to know which knob does what if anyone knows. also, i had to put a new bridge on my bass about 2 years ago but as my ear has got better, i have noticed that some of the notes played past the 12th fret are slightly sharp. is this common? is there a way to fix it? thanks in advance guys.