I picked up a bass that came with Duncan quarter pounders. I pulled em and put em in something else. Here's the problem. The bass was fine with the pickups before I put the Duncan's in so I know there is no issues with the electronics. Ok, so, with just the J on, it's fine. With just the P on it's fine. If I have both on full, there is something strange with the J. The E and A strings sound fine BUT the D and G, and only those, sound super thin, as though I turned all the bass off. Again, ONLY with both pickups on. I wired white to the center lug and black to the pot case, like all of my basses. I did try flipping these 2 wires .the problem is gone but it now has this wierd sound, much thinner, ALMOST like there is a hint of...wah! ***???? I've changed pups, rewired basses many, many times, never came across this issue. My thought was maybe the pick-up is bad, but then it should always be bad right? Totally stumped on this .