I've got a fully functional bartolini mk-1 active soapbar pickup that I'm trying to run to straight to the jack (no knobs). This is in a 6 string project fretless bass of mine and it's the only pickup that is on it. The problem is that when it's hooked up, powered, and grounded properly, only the low notes work (this is a 6 string fretless.. so b-e-a) and the d-g-c don't have any output. I'm not sure how to fix this.. I've tried a few combinations of wiring on the output jack but with little luck. Any help? Do I have to have tone/volume knobs? This will sound really nice once I get it working and i'm curious as to what the problem is.. Thanks.