On my Eastman mandocello recently installed this magnetic pickup along with this volume and tone pot combo. All wired up per directions with a shielded pair. The hot + lead from the pu goes to the pot combo + in, then from the pot combo + out to the tip connection on the TRS output jack. The "-" lead from the pu goes to the pot combo "-" in which is also the "-" out. The "-" out goes to the sleeve or ground of the TRS output jack. The shield, per the directions, is not connected to the pu. It connects to the "-" in/out of the pot combo and on to the sleeve/ground of the output jack.
The pickup and pots work fine and sound good. However, when plugged in I get a hum (more of a quiet buzz) coming from the amp (Carvin AG300) if I touch the pickup. When I connected a ground wire from the "-" in/out of the pot combo to the body of the pickup (not to either of the output connections) the signal is completely killed (although it no longer buzzes when I touch it). I've never had this happen when wiring up a magnetic pickup in a solid body electric. This is the first mag pu I've installed on an acoustic instrument. The location of the the pu is such that I don't touch it unless I want to (not in the way of normal playing). I'll see if I can get a legible pic of the wiring directions here later when I get back from work. Any thoughts or suggestions? Thanks.