I recently put together a Warmoth Fretless bass and used Bartolini pickups with the build. Precision pickup was a 8CBP pickup Jazz pickup was a split coil 9J-L1 I used this wiring diagram http://www.bassemporium.com/pdfs/pjbassstandard.jpg I used 250k audio taper pots and had a luthier check my work as soon as gremlins showed up. It all checks out OK. My problems are as follows: 1. When the P bass pickup is full up and the J pickup is added to the mix, it loses low end and the bass is somehow cancelled out, leaving a more J like tone. Frustrating when just adding the J pickup for seasoning as I like to do. 2. The taper of the pots seems off. Both pots are extremely low volume until the last tiny bit of the range of the pot. I thought this might be due to a wrong taper pot but after replacing them, the problem remains. 3. While the resistance of the pots checks out on a meter and they both adequately zero out any signal while on the meter, the bass has a low volume even when the pots are completely down. I am completely out of my depth here, I do not understand these problems, and while I can solder a circuit well (electrician dad - he is stumped too) I can't see any reason other than using a wrong wiring diagram that these problems are occurring. Any ideas?