I picked up a new bass today (an Ibanez SRF705 "Portamento" fretless, with two Bartolini MK-1 split-coil magnetic pickups and piezo-pickups under the bridge saddles). It's great, but when I sit in front of my computer and turn up any of the magnetic MK-1 pickups and set the treble pot anywhere except for full-cut, I get a pretty nasty hum. I don't think it's a single coil hum because the hum is the same whether one pickup is on, or they are both at max. It also doesn't seem like a shielding issue because it doesn't matter if my hand is on or off the strings, bridge, or potentiometers. However, if I spin around in my chair and face in a certain direction, the hum pretty much completely goes away, even if I fully boost the treble pot. Is there anything I can do so that the hum is gone no matter which position I'm sitting? Thanks!