Brass or Copper Cavity Cover?

Discussion in 'Tone Zone' started by Robert Herndon, Nov 23, 2016.

  1. Robert Herndon

    Robert Herndon Well-Known Member

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    Was just thinking...wonder how this would work??? We use copper tape, right??? I suppose one could surmise that most interference would come from the front of the instrument, but then why shield the floor of the routs???
     
  2. Raiyn

    Raiyn Well-Known Member

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    RF energy is all around. The purpose of shielding is to create a Faraday Cage to block any stray signal. Uncovered pickups don't help this, but shielding the bottom of the routes takes out a big section of potential interference. Same goes for the cavity. Shield the floor, walls and cover.
     
  3. donepearce

    donepearce Well-Known Member

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    If you use canned pickups there is nothing to be gained shielding the pickup routs. For the control cavity it is the back cover that is most important to shield. The human body acts as a giant antenna that will feed hum into that cavity better than anything, and it feeds it in through the back.
     
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  4. DrBGood

    DrBGood Well-Known Member

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    What is the usual interference source ? The electrical circuit in which your amp is plugged in ? I never understood the cavity shielding concept, if the problem source is through wiring.
    Or is the interference coming through the air ?
     
  5. Raiyn

    Raiyn Well-Known Member

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    Live and on air Doc.
     
  6. Chubbles

    Chubbles Active Member

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    The source is all around, lighting, anything not grounded. I used copper tape from Amazon.
     
  7. Robert Herndon

    Robert Herndon Well-Known Member

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    Some venues are worse than others!
     
  8. donepearce

    donepearce Well-Known Member

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    Question. Does the buzz go away when you touch the guitar metalwork? If yes, get grounded copper onto the control cavity cover.
     
  9. Raiyn

    Raiyn Well-Known Member

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    Best way to do that is by contact with a shielded cavity......
    [​IMG]
     
  10. donepearce

    donepearce Well-Known Member

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    Absolutely the best. But just shielding and grounding the cover is surprisingly not a great deal worse. I might be inspired to do a video comparison of different levels of shielding.
     
  11. Raiyn

    Raiyn Well-Known Member

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    If you're taking the axe apart for a rebuild, no sense in half-assing it. Shield the routs and covers and connect them all to the common ground.

    In fairness, in an effort to control the ground connection and avoid loops at all costs I took this to an extreme on mine: the pots, jack, and switch are all insulated from the shield. The only connection is that flattened and tinned bit of outer braid off the bridge tone pot. I've also rewired my axe since the picture simplifying the switch to jack connection I kludged the first go 'round by failing to connect the pots to the ground due to exhaustion. It worked, it just wasn't "right"

    Failing that, I fully concede that a insulated wire soldered to a copper covered cover and to a pot would help if a complete cavity extraction isn't in the cards. Just keep the wire as short as practicable.
     
  12. donepearce

    donepearce Well-Known Member

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    Your point about avoiding ground loops is well taken. When I rewire I use the star ground method with everything grounded to the jack socket ground. By the time you have the cavity sorted that is the cherry on the icing. Of course the pickup routs can't be screened. All you can have is some copper behind the pickups. That is useful at least in preventing body-induced noise.

    Of course you can then render the whole exercise pointless by fitting P90s, but hey-ho.
     
  13. Raiyn

    Raiyn Well-Known Member

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    Yeah, everything in mine currently (!) goes to the ground lug of the switch then out to the jack with that same tinned braid still being the only contact with the shield.
     
  14. DrBGood

    DrBGood Well-Known Member

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    Really ?
    Your gastro-intestinal gurglings come through the amp speakers ?
     
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  15. Raiyn

    Raiyn Well-Known Member

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    You'd be surprised!

    Although in fairness, due to body chemistry, I AM a human antenna. As an example, when I was a kid I liked to listen to radio stations that were 90+ miles away up to around 250 ish if I could get the Twin Cities to skip for me.

    One day, many years ago, I had gone to the bathroom and left the radio on in my room. Meanwhile, my mother had gone into my room to hang some clothes up for me and was only able to hear some soft static from my radio. When I entered the room behind her suddenly the radio came blaring to life scaring the living bejeezus out of her. On top of that, like my father, I can't wear battery driven analog watches, they die permanently in fairly short order. Unlike my Dad however, I never bothered with purely mechanical watches so I have no idea if they'd work for me.
     
  16. donepearce

    donepearce Well-Known Member

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    Hmmmm...
     
  17. Raiyn

    Raiyn Well-Known Member

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    [​IMG]
     
  18. DrBGood

    DrBGood Well-Known Member

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    My wife has that, it's called hypo-galvanism. Your body produces too much electricity. Her watch batteries, like yours, don't last more than a month. Therapist looked at her mouth and saw a gold filling in one teeth. She told her that there was some kind of flow between that and her gold wedding ring, and that is what kills the batteries. She took her ring off to test the theory and the watch batteries now last.

    I told her that if I ever get a pacemaker, I'll have to divorce her or she'll surely kill me.
     
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  19. donepearce

    donepearce Well-Known Member

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    I'm holding my tongue as hard as I can.
     
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  20. Raiyn

    Raiyn Well-Known Member

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    Digital watches work fine, and the batteries last just fine. The mechanical ones just stop and never work again, new battery or not.
     

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