string buzz with Ultra Jazz pickups and audere preamp

[mrscotch]

I have a Lakland Darryl Jones 4 string that I first swapped in Dimarzio Ultra Jazz pickups and then later installed an Audere preamp. Now I get a buzzing sound whenever my hand is not on the strings. I was thinking it was a grounding problem, but I recently rechecked the wiring and it seems to match the instructions exactly. The pickups have 4 wires each, with the red and green going to the preamp and the black and white tied together as per Dimarzio's instructions. The bridge's ground wire is connected to the wire Audere says to connect all grounds to. Any ideas?

Thanks for your help.