Strange hum/interference from PJ

Discussion in 'Pickups & Electronics [BG]' started by JT Foster, Apr 7, 2022.

  1. JT Foster

    JT Foster

    Dec 27, 2014
    O’Fallon, MO
    So I’m having a lot of hum with my rig lately. It got a little better when I switched from going directly into multiple wall outlets, to using a power strip. However, it’s still humming really loud even with my ZNR gate all the way up. It goes away if I point my bass face down, OR if I am touching a metal part of the bass; such as the strings, the bridge, the tuners, or the control plate.

    Very strange.

    It’s not the end of the world, I can still enjoy playing; but the fact that it goes away when I’m touching the metal parts of the bass is confusing to me. The ground switch on my headphone amp has no effect over it. Thoughts?
  2. dwizum


    Dec 21, 2018
    This is a classic indicator that there's a lot of noise in your environment and your bass is not shielded well enough to reject it (it's also a good indicator that the ground wiring inside the bass is intact). Your body is conductive, when you are just standing there (not touching the bass) you're picking up noise signals and reflecting them back out. When you touch metal on the bass, the metal (which is grounded through the ground lug on the jack) provides a path to ground, and the noise your body picks up gets sent to ground. Essentially, touching the metal parts on your bass turns your body into a giant shield, which is protecting the bass from the noise in your environment.

    What you need to do to solve this is add shielding around any part of the bass in the signal chain - the pickups, the hookup wires from the pickups to the controls, the controls, the wiring in the cavity, and the jack. Having that complete path well shielded is the best solution to noise problems. This way, the bass is well shielded on it's own and doesn't need your body to act as a shield.

    You may also want to have an electrician check out the wiring on the outlets you're using, if you get a different result based on plugging in to different outlets there may be a problem in your home's wiring that's contributing to the noise.
    JT Foster likes this.
  3. JT Foster

    JT Foster

    Dec 27, 2014
    O’Fallon, MO
    Very interesting! I’ll have to look up how to add some shielding to my bass cavities.

    Thanks for the advise, buddy!
    dwizum likes this.
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