I decided to put some DiMarzio Model J's in my Jazz bass, to shield the control cavity and also rewire the controls to Volume-Blend-Tone. I have attached the wiring diagram I worked from. Shielding the cavity was no problem. Then I installed the pickups into the body of the bass, no soldering yet. Lastly, I proceeded to wire up the new pots according to the attached diagram....and then finally I attached the pickup leads. Initially I chained all the grounds in the diagram (and the bridge and pickup plate grounds) and had them run to a single ground, the standard Fender one screwed to the body, from the back of the volume pot. Then tried it out...everything functioned as it should, but there was humm. Next I tried installing more grounds, separate ones for each pot and from the jack (as well as the bridge and pickup grounds), this time running them directly to the shielding foil. 3 points in total two wires to each solder point, and I left the standard Fender screw ground in too. Plugged in again and still humm. I hope someone can follow what I am saying...I know it is hard without actually seeing it. Other considerations : the two other wires from each pickup, black and white, are connected - for humbucking series. The bridge ground is in tact. I think I am going to let it sit for a few days and then revisit it...but I figured I would post to see if I missed something completely obvious.