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Pickup Shielding

Discussion in 'Pickups & Electronics [BG]' started by seanm, Jan 26, 2006.


  1. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    I have picked up a really bad hum problem on two of my P basses. As long as I keep a finger on the strings, I am ok. Neither bass is shielded at all. My third shielded bass does not have the same problems.

    So I am checking out the one and notice it does not have the metal plate under the pickups. How important is this plate for reducing hum?

    I twisted the wires from the pickups togeather and wrapped them in tinfoil as a poor mans shielding. I then wired the pickups straight to the jack. The bridge ground already went straight to the jack. That didn't seem to help at all.

    Does the tinfoil mimic shielding (I have it wedged so it is grounded)? I could try switching to coax but I don't want to risk unsoldering and soldering the pickup end unless it would help.
     
  2. momo

    momo

    Oct 22, 2005
    Huntington Beach, CA
    I just shielded a MIM jazz with aluminum foil and it did wonders. Would copper have worked better? Quite possibly, but I didn't want to order a $17 shielding kit from stewmac and wait for a week to get to me, so I used about a square foot of aluminum foil and some elmers glue. I think the problem that you are having is that you need to shield the ENTIRE pickup and control cavity. Just wrapping the wires in foil might help, but try the rest of the cavity. Also shield the bottom of the pickguard in the area directly around the pickup. The only thing I didn't shield on my bass was the hole between the bridge pu and control cavity, and guess what, only the pridge pu hums now.
     
  3. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    momo, I think you are right. I need to actually sit down and do the job right rather than trying to do something simple.
     
  4. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    Grounding plates can help reduce hum in pickups that have magnets that are in contact with ground if the ground plates contact the magnets.

    Aluminum is a conductor not an insulator and wraping it around twisted bare pup wires will induce a current flow through the foil. Electrical tape or wire nuts will work but are substandard to the shrinkwrap that should be used for bare wire connections - and it's available at Home Depot for a couple bucks.

    You can use aluminum foil for shielding (not insulation) but it's cheap, substandard, does not lay flat (and therefore more prone to shorts), tears easily, and looks as cheap as it is. I've done both. Foil is of some use if you just want to do a quick check to see if shielding will help - often it won't cause it's for external interference and the problem is more often internal. You can throw foil down in a P bass and rip it back about in 15 minutes or less. Copper took me several hours my first time.

    Even if external interference is not the current problem, since the bass moves around, shielding may improve performance significantly elsewhere.

    Plain old pvc insulated wire comes on some of the best pups leading manufacturers make.
     
  5. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Thanks for the info. I broke down and shielded one of the basses with copper. However, I now have shorted the output. It is too late to fix it now, so I will try to get it going tomorrow.

    One advantage of the MIM P is that they route out the passage from the control cavity to the pickups rather than drilling a hole. Makes it much easier to shield.

    So I shielded the bottom of the pickup route, all of the wire run and the control cavity. I also added shielding to the pickguard and folded over some shielding from the cavity to contact the pickguard. I sure hope this works.
     
  6. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX
    FYI, if you don't want to pay the $17, I found a roll of .003" thin copper sheet that was about 12" wide by at least 6 or 8 feet long at Hobby Lobby for about 8 bucks. Nice and clean, solders like a dream. That and a can of spray contact cement, and I have done my bass as well as the kit would, and I have enough left for at least 10 more basses. A bit more work, needing to spray the glue on the copper after you cut to size, but not much . . . and since the foil is so big, if you want to do the entire back of the PG, you can do it in one piece, unlike the 1" and 2" sticky back rolls . . . .

    - Tim
     
  7. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    If you still have a bit too much noise, you can also change the grounding pattern. Star ground is amazing for keeping noise to a minimum. I just wired a guitar today with no coax, and it is dead silent.
     
  8. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    I was thinking of trying that next if this dosen't help.
     
  9. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Oh, there was no shielding in the guitar, either.
     
  10. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    I threw down a piece of electrical tape under all pot lugs and on any bay wall where a hot lead might possibly make contact. One of the downsides of shielding is it's pretty ideal for shorts. As much as Sadowsky is a proponent of it he cautions about shorts.