Shielding a guitar: fact vs myth

Discussion in 'Luthier's Corner: Guitar & Bass Technical Discussi' started by Terry McInturff, Feb 8, 2011.

  1. Terry McInturff

    Terry McInturff Member

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    Hello all,

    I am a firm believer in shielding a non-vintage guitar as completely as is possible.

    What is meant by shielding? It means that...as much as is possible...the pickup cavities, the pickups, the controls...are all surrounded by an electrically conductive metal foil, paint, etc that is grounded. A good job of this will substancially reduce the amount of Radio Frequency (RF) buzz and interference that will come out of the speaker cabinet.

    It can make a big difference. All sorts of RF can create havoc...not only from radio stations, but also from light dimmer packs, flourescent lighting, and even digital cash registers!

    While I personally recommend conductive paint..applied liberally, in multiple coats...adhesive-backed foil can work too.

    Main aim...surround all components as much as is possible...test to make sure that all shielding is connected to ground...also to make sure that no accidental grounding-out of any component can happen via the shielding should a securing nut happen to come loose, etc.

    Myth: Shielding will change the tone of the guitar
    This is only true if you consider RF noise to be a part of the musical tone of a guitar. I consider RF to be unmusical noise. Totally undesirable.
    Common error: not doing a neat and thorough job, not grounding the shield properly
    Remember that the goal is to surround the components with what amounts to a grounded, conductive enclosure...technically, a Faraday Cage. The shield must readily conduct electricity (test with a VOM) AND be connected to ground via sturdy means.
    Tip: how to paint internal wire holes
    Pipe cleaners make a good "brush" for this.

    Shielding will not detract from your tone. Arguably, the tone will be improved.

    Great shielding + Excellent electrical components + world-class wiring = totally professional work "under the hood" :)

    Im painting on shielding today, and so this topic came to mind.
     
    Last edited: Feb 8, 2011
  2. Diablo

    Diablo Member

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    Hey Terry,
    Great post idea once again. I have always found that the single coil guitars, especially P90s, benefit a great deal from sheilding. Humbuckers, I haven't noticed so much. I have done it with copper tape soldered together which works quite well. What kind of sheilding paint do you use and where do you get it? I have used the Stew Mac stuff before but it was quite expensive for such a small amount if I recall. I have looked at industrial electric supply places but didn't know exactly what to ask for. I'll have to do some testing now that you brought this up regarding humbuckers and sheilding. Thanks again for the informative posts buddy!
     
  3. amc

    amc Member

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    once again, thank you terry for your informative post......................

    as a side note: i own and happily play instruments built by both terry mcinturff and joe driskill (diablo).
     
  4. Terry McInturff

    Terry McInturff Member

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    Thanks Joe!
    I do use the paint from Stew-Mac; it is from Germany and is called Electrodag. Maybe we can find a good OEM source.

    I agree that the biggest benefit is on single coil equipped guitars; but humbucker-equipped benefits as well, due to the fact that any unshielded wiring in the control cavity picks up RF.

    One thing that I see time and time again is an OK shielding job in the guitar...but the underside of the coverplates arent shielded.

    I also see conductive paint that does not make a clear ground all the way to the jack. This is usually due to not applying enough paint...and obviously from not testing it with a VOM after the paint is dry!!!

    Just MY opinion...these are electric guitars...isnt it right to expect outstanding electrical craftsmanship?
     
  5. claycastle

    claycastle Member

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    I completely shielded the interior guts of a Kramer Focus (pick guard with single coils)with the copper tape. Took quite some time to do it right. No difference! Still makes the same noise. Still gets the same interference.
     
  6. Pfeister

    Pfeister Member

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    Did you ground the shielding to the rest of the electectronic setup? That's absolutely necessary.
     
  7. Terry McInturff

    Terry McInturff Member

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    This could be due to:
    1) An expectation that shielding will reduce 60Hz hum..it will not..only RF
    2) Your shielding isnt grounded well
    3) A ground loop in your guitar's circuit
    4) A ground loop in your system
    5) On and on...
     
  8. Ahess86

    Ahess86 Member

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    Hi Terry,

    This is a relatively new and interesting topic to me. I'm curious, how do you connecting your shielding paint to ground?
     
  9. Terry McInturff

    Terry McInturff Member

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    At times Ive relied upon the cases of the pots, switches, etc to make the connection, but I have to say that this is not the very best way. The BEST way is to solder a wire to a lug, solder the other end of the wire to a good ground, screw that lug to the wall of the control cavity, and then paint over that connection. This...plus the connections gained from the pot cans, etc...is best. IMO :)
     
  10. frquent flyer

    frquent flyer Member

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    I have heard of copper foil and/or a carbon based spray being used...I know shielding works well..more builders should use it.
     
  11. Terry McInturff

    Terry McInturff Member

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    I agree that good shielding ought to be S.O.P.

    The carbon based sprayed paint is OK...however, it can go on too thin, and not be a great shield. Of course, more coats can be applied. There are sprayable metallic-based paints, and these seem to provide a better "one-pass" result.
     
  12. AudioWonderland

    AudioWonderland Member

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    Oh Hell I went nuts and did 3 coats of stewmac paint and then applied Stew mac copper tape with the conductive adhesive over the paint on my strats. It was everything I wanted and more. The noiseless pickups just did not sound right and the DAW CRT still caused issues. After shielding I had to locate myself so the pickups were off access from the CRT but once I did it was quiet. I later replaced the CRT with a flat screen and it got even better.

    I have always felt like just a tiny bit of treble is lost when the shielding is done but I also consider that a plus. Strats always seem a touch bright to me
     
  13. Pscheoverdrive

    Pscheoverdrive Member

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    If you REALLY trusted your shielding job, you could theoretically just ground everything to the shield... Pots, pickups, bridge, output jack, etc.

    I used to use aluminum foil and spray-glue on some of my early guitars. It actually worked pretty well and was a heck of a lot cheaper than shielding paint or tape, but looked pretty DIY.

    Maybe somebody should start making metal pickup cavities and control cavities that could just get dropped into the guitar, and then grounded. I'd trust something like that for a ground-to-chassis kind of wiring job.
     
  14. Terry McInturff

    Terry McInturff Member

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    Agreed. The only reason why grounding to the shield isnt a great idea is the probs regarding connections to the shield..especially with paint. But yes...a good shield is essentially part of the ground bus.

    For a number of years, Gibson fitted LP's etc with a metal can for the control and switch cavities. These worked well.
     
  15. Pscheoverdrive

    Pscheoverdrive Member

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    Better than those POS PCBs in them now, I imagine... :\
     
  16. rah3

    rah3 Gold Supporting Member

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    Come on Terry! Noise is an essential element in the Sonic Pantheon of Rock and Roll guitar!

    - RAH3
     
  17. Tidewater Custom Shop

    Tidewater Custom Shop Performance Enhancing Guitarworks Gold Supporting Member

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    My current Strat is the most quiet I ever owned. It didn't start off that way. I had a full aluminum shield and everything properly grounded, but it still had some issue that would go away when I touched the strings or anything metal.

    So, I got a small can of that StewMac stuff and applied 2 coats to the pickup cavities, the elex compartment, even the output cavity. After it was dry (next day), I reattached my ground strap (from the pickup ground cluster on the V pot) to the elex cavity side wall and buttoned it up.

    To me, the StewMac paint was the magic touch. Call it snake oil, but my Don Mare pickup loaded Strat is almost as quiet as my properly grounded humbucker loaded Les Paul. My Telecaster is next for the treatment!
     
  18. claudel

    claudel Member

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  19. Oz Hofstatter

    Oz Hofstatter Gold Supporting Member

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    Thanks for share Terry!
    Best,
    Oz
     
  20. Super Locrian

    Super Locrian Member

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    I'm in Norway, I don't think I can order chemicals from abroad. I've found some Electrodag products available locally, which of these would you recommend (link to datasheets)?

    Electrodag 440 AS

    Electrodag 1415M

    Great topic, thanks for the very useful info!
     

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