getting rid of hum with piezos

Posted by Michael Recchione on April 6, 2013 at 5:01pm

I've been getting an annoying hum with all my CBGs when I turn up the amp gain.  The cable I've been using is reasonable quality, but has metal jackets on the plugs.  When I touch the plug housing, the hum goes away, meaning it's a grounding issue.

I had heard (read here on CBN) that you don't need to ground the saddle or bridge with piezos, so I didn't.  But now I'm wondering if I should have done that.  I'm also wondering if a different cable might help - maybe something without a metal jacket that essentially brings the ground plane outside the guitar...

Anybody have any experience with this kind of amplifier hum, that can maybe offer an elegant way to get rid of it (short of wearing a grounding bracelet when I play...)?

Thanks,

- Mike

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Replies

  • Jon Leslie/Runaway Veal Music April 8, 2013 at 2:18am
    I'm not sure grounding your arm is good. Anything else is better even a hum. Try smashing the pickup or re wiring it
  • Dave Lynas April 7, 2013 at 4:30pm

    I don't think you'll need to be the ground with a bracelet on your wrist... sort of like an electric chair idea.... The grounded system should do it without touching the strings yourself. You get little chirps when you touch the strings when things aren't right which adds an unwanted sound. Once you finally get everything grounded it should do it without your being the ground. I've been frustrated trying to find where my ground is deficient, but once you find the culprit, the sound gets much better with silence when not playing.

  • Dave Lynas April 6, 2013 at 8:56pm

    Since i build with wood mostly, i have to ground my bridge or tailpiece with some metal strip added. It's worked good and is easy. I've grounded to the jack or better, to the back of the volume pot. If i have a grounding hum coming till i become the ground by touching a pot shaft or jack nut, i just add a ground and it goes away. You can try a simple jumper from your jack nut to the strings to test the idea.

    • Michael Recchione > Dave Lynas April 7, 2013 at 12:24pm

      "You can try a simple jumper from your jack nut to the strings to test the idea."

      Exactly what I was planning to do...  Thanks!

    • Michael Recchione > Michael Recchione April 7, 2013 at 1:56pm

      Update:  I tried that, and it worked - at least as long as I was touching the strings.  I use open tunings on CBGs, so it's not a perfect solution.  After grounding the bridge, I tried making a grounding bracelet from some picture hanging wire I had lying around, grounding the jack case to my wrist.

      This worked perfectly.  Of course.  It sounds so good I can't NOT do it.  And just when I thought it was not possible to look dorkier than I already did ... :D   But I guess if I were really worried about how dorky I look, I wouldn't be be out in front of people, playing a tiny little guitar made from a cigar box... lol.

  • Jon Leslie/Runaway Veal Music April 6, 2013 at 5:14pm
    I've had to rewire the piezo a few times make the wires real small and in one stubborn buzz hum sorta put pressure on the piezo...it's the only one that did this so the piezo might have been defective...
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