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Hum - bass, amp, or house wiring?

Discussion in 'Pickups & Electronics [BG]' started by DrVenkman, Nov 12, 2010.

  1. DrVenkman


    Jan 22, 2010
    Pacific NW
    I'm trying to track down the source of a hum I'm getting, and am turning to the experts here. The situation:

    - the hum is reduced 95% when I touch any hardware on the bass, or the metal connector on the cable
    - it's happening in the room in the house I use for practice; I've had the amp and bass in a half dozen other places and not noticed the hum anywhere else
    - the bass is a CV Jazz, and the amp is a GK MB210. I've had the control plate off the bass and everything seems grounded and it looks like it's got shielding paint in the control cavity
    - this buzz is with both pups full on; I do get some buzz just about everywhere if I don't have both pups on, but that's expected

    Since the hum pretty much goes away when I touch any hardware on the bass, it seems to me the bass must be grounded OK, but that's just my inexpert opinion. I've tried a different cable with no change, so it doesn't seem to be the cable.

    The one thing that occurs to me now is that the light in that room is on a dimmer and that may be causing me problems; I'll play with that later. I've played other places with dimmers without the buzz but maybe they were different brands, or I was farther away from them. Now that I've thought of it that's my prime suspect.

    My concern is that it's the ground wiring in the house. I've got a multimeter but no other kind of test gear - is there any good way to check the wiring without buying a circuit tester? Or if not, any recommendations on a good circuit tester?

    And the overall question - what do you think is the source of the hum, how can I find the source, and what can I do about it?

  2. darkstorm


    Oct 13, 2009
    Check the electric wall sockets to see if the 3rd prong ground is actually functional.
  3. mech

    mech Supporting Member

    Jun 20, 2008
    Meridian, MS, USA
    If the hum is reduced when you touch hardware on your bass it is grounded. I would also suspect the light dimmer especially if the hum has more of a buzz sound.

    Get a wiring fault indicator at an electrical store or hardware store to check the house wiring. I keep one in my gig bag and always check wiring at new venues. Doesn't have to be an expensive one. Here are some examples.



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