1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Reducing Locational Hum?

Discussion in 'Pickups & Electronics [BG]' started by Matthew_84, Nov 22, 2018.

  1. 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?

    Last edited: Nov 22, 2018
  2. Check for continuity between the bridge & the output jack.
    You'll need a Ohm meter or a multi-meter that can measure Ohms.

    Those MK1 pickups are quiet. I just had a SR600 for one night that had MK1 installed & it was very quiet, even in my noisy environment.
    The noise is probably being induced into the controls cavity & not the pickups.

    My G&L L-2000 was noisy in front of my computer, until I connected the foil on the controls cover to the cavity shielding.
    Matthew_84 likes this.
  3. Thanks KBD! I’ll check that out tonight.
    Killed_by_Death likes this.
  4. tektsu


    Nov 8, 2018
    My new SR375EF has exactly the same issue. I'll be checking out that continuity. Thanks!
    Matthew_84 likes this.
  5. @Killed_by_Death, so I have about 650 ohms (which I realize is too high) between the bridge/strings and the jack. I have about 1.2 k ohms (on average, these numbers bounce around a lot) on the pots.

    I opened up the control cavity and first was happy to see the back of the plate covered in foil tape, and the cavity painted black (which I assumed was conductive paint), but there's like 1.1 k ohms between the paint an inch apart, so it's just normal paint.

    That explains the problem... If you're going to paint it anyway, I don't understand why you wouldn't use conductive paint... Seems pretty silly on a $1300 (CAD) instrument.
  6. On my G&L L-2000 there was 500 Ohms between two points only 20mm apart, but the shielding worked.
    There shouldn't be so much resistance between your bridge & your output jack, however.

    Make sure the foil of the cover is contacting the shielding paint.
    Matthew_84 likes this.
  7. It’s only making contact by the pressure of the three screws holding the plate down. There isn’t a wire or anything to ensure a good connection. I’ll look into adding something. Thanks @Killed_by_Death, I appreciate it!

    I added a picture of the cavity if you or anyone else is interested.

    Killed_by_Death likes this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.