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Braided outer shield question

Discussion in 'Tele-Technical' started by Wallaby, Apr 23, 2020.

  1. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I'm considering deconstructing some Gavitt wire that I have to remove the braided outer shield, then use that to surround the twisted leads from my SC neck and bridge pickups in my guitar.

    My goal is to reduce RF interference.

    I *think* I need to solder at least one end of the sheath to ground, if not both ends, but I also think I've read somewhere that aluminum screen can block RF interference.

    So I thought I'd ask the experts -

    - Do I need to solder zero, one, or both ends of the braid?
    - Any drawbacks to this approach? I'd rather try this than install shielding

    ( I am also going to install shielded output wire from the volume potentiometer to the jack while I'm in there )

    Thanks,
     
  2. wabashslim

    wabashslim Tele-Afflicted

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    Sounds like a lotta work to "deconstruct" some wire to make another wire. Easier just to replace the twisted leads with the Gavitt. If its single conductor you'll need to solder at both ends. Even if its a shielded pair you'll want to connect the cover or bridgeplate to the shield.
     
  3. chezdeluxe

    chezdeluxe Poster Extraordinaire

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    If you decide to do it you only need to solder one end to ground.

    The Neck pickup cover and the bridge assembly will remain grounded via the existing pickup wires.
     
  4. AAT65

    AAT65 Friend of Leo's

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    You can buy screening braid easily enough in a variety of diameters — in the UK RS or Farnell sell it, I’m sure there’s a US option too.

    You must ground the braid, otherwise you’ve just installed a big antenna in your guitar to receive noise with. In the guitar body I don’t think it will make any difference whether you ground at one end, both, or somewhere handy in the middle. (There are cases where screens should only be grounded at one end but I don’t think it makes any difference in a guitar, which is small and very low-current.)
     
  5. moosie

    moosie Doctor of Teleocity Silver Supporter

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    You don't need to shield the common. Just the hot.

    I've done it that way, like this:

    Pickup shielding hot lead crop.JPG


    Tease the end into a lead, and solder to the cover ground point (or baseplate here). Finish the other end with some copper foil, and a small bit of solder.

    Warning, it can be a pain to do. But I didn't 'deconstruct' the braid. I just slipped the wire out. Now, it would have made a lot more sense to just use the hot lead the braid came with, but i didn't want to replace the hot lead that came with the pickup. If you're willing to do that, easy peasy.

    Here I just shielded it long enough to reach the cavity, where it will be shielded by cavity shielding.
     
  6. sjtalon

    sjtalon Doctor of Teleocity Ad Free Member

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    I don't know if your cavities have any shield, or more importantly the pickguard (which is the part that would do THE MOST shielding), but all you are
    going through to get about 6 inches of wire shielded really doesn't amount to doing much good.

    The pickups are naturally the MAJOR EMI/RF antenna, those leads don't really matter that much to worry about.

    .02 and such as.
     
  7. jvin248

    jvin248 Poster Extraordinaire

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    .

    I find about half the idle noise of a typical guitar can be cleaned up with shielding the wires to the jack. The other half with proper cavity shielding. Yes, ground at least one end of the over-wrap (one risk is shorting out by touching other parts of the circuit, so you should tape over any potential problem areas).

    There is no harm in running shielded wire inside the guitar rather than cavity shielding. If you take apart a $100 Epiphone Special II (discontinued last year) you will find shielded cable on both pickups and from the volume pot to the jack. Meanwhile, top end Fender Strats have push-back cloth wiring on everything and suffer from extra noise in addition to the single coil problem since those folks back in the fifties thought we'd use flying cars and never dreamed of cell phones and laptops and their electric noise.

    The next layer of noise reduction comes from shielded pickups like chrome covered humbuckers or Tele neck pickups.

    Here is the wiring in an old relic guitar I have .. humbucker > volume pot > jack. Signal wire to the jack is shielded cable (blue wire in the picture) that I pulled from a scrapped desktop tower computer's audio signal line from the CD/DVD player. The black wires are the shielded pickup wire and the unshielded bridge ground wire.

    If shielding guitar signals wasn't important, we'd all use cheap twisted pair wire to the amp and not the expensive shielded cables we seem to need.

    [​IMG]


    .
     
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  8. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    Thank you for the responses and your points are well taken, I really appreciate it!

    I'm going to start with the output to the jack and see how that goes.

    I am trying to avoid tampering with the existing leads on the pickups, plus I have a surplus of the braided-shield wire and I'm familiar with using it from rewiring an ES guitar.. repeatedly :)
     
  9. Blue Bill

    Blue Bill Poster Extraordinaire

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    Cable shielding should be grounded on the end closest to the amplifier.

    I suggest trying it without elaborate shielding, you may not need it. I've had many guitars with non-shielded and not even twisted wiring, that are quiet as can be.
     
    Last edited: Apr 24, 2020
  10. moosie

    moosie Doctor of Teleocity Silver Supporter

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    I have good experience doing something to shield the neck hot lead - however it's done. The issue for me seems to be not RF, but static on the plastic pickguard (not bakelite). When my fingers touch the guard, lots of static through the amp. I could shield the whole darn thing, but simply twisting the neck leads tightly helps a lot. Shielding the hot with a braid, or heck, wrapping copper foil around it, or replacing it with a piece of coax... works extremely well.

    If the concern was more about RF, I'd probably have better luck shielding the entire cavity, but from where I sit (literally, I play at home, in one chair), it's the static that's the problem.

    Tightly twisting the leads to the jack is a good thing, too. Standard procedure for me.

    One of these days I'm going to think more like a Gibson or Gretsch guy, and wire a complete Fender with all shielded leads. No cavity shielding, and it'll be DEAD silent. Historically, why don't we do that again? All because bakelite was a good insulator, and because Leo was cheap, and the runs were short? Not that short.
     
  11. sjtalon

    sjtalon Doctor of Teleocity Ad Free Member

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    Hey mossie, get ya one of these for that chair:

    [​IMG]
     
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  12. schmee

    schmee Doctor of Teleocity Silver Supporter

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    I've not needed to shield SC's with the rest of the guitar shielded, but it cant hurt. One end if you are not using it for ground. I use shielded input wire, grounded one end.
     
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