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I just recently built a Les Paul style guitar, and, for some reason, when I touch the pickups and selector switch the guitar stops buzzing.

Why?

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2 Answers 2

That is normal.

The strings are earthed so when you touch them your body becomes earthed and no longer acts as an antennae and electrical hum is reduced.

Nearly every other conductive part on a guitar should also be earthed for noise reduction reasons.

If a part isn't earthed and you touch it (while not touching something that is earthed..) the hum will generally increase.

If the hum reduction when touching the pups/selector still occurs when you are already touching the strings that would imply your strings are not earthed. Did you run a wire from one of the bridge post holes to earth?

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1  
Not so common for humbuckers in fact (standard pickups with Les Pauls)... Agree when using single coil pickups. –  scrowler Mar 3 at 5:16
2  
@scrowler If you are implying that humbuckers are quieter than single coils, then I agree that is generally true, their construction cancels more EMI. If you are implying earthing issues (which the OP describes) are "not so common for humbuckers" then you are wrong. The quality of the earthing has nothing to do with the pickup type installed. –  Fergus Mar 3 at 9:05
    
There are very valid reasons why guitars should not have their strings (or tuners, bridges or other metallic parts) grounded. It creates a situation where the guitarist can close a loop through badly wired A/C circuits, which can cause a shock, or even death. It's better to shield the controls and possibly do what Taylor does in their electrics, and use a shunt that'll open in case of a ground-loop. Modern building codes should having wiring that won't case a problem, but old buildings, or badly wired stages, can be dangerous. –  the Tin Man Mar 5 at 0:09
    
@theTinMan Your reasoning can be applied to all appliances, yet my toaster, oven and computer (and guitars of course..) all have their metallic cases earthed, and for good reason. If there is a fault and the casing becomes electrified a large current will flow via the earthing system and the mains fuse (or RCD/GFCI) will blow and the current will cease to flow, this occurs pretty much instantaneously. If the part was not earthed it will remain live until something with a viable path to earth touches it, usually the user... –  Fergus Mar 5 at 3:41
    
As for Taylor, they still earth their strings, the only difference is that it is via a 10 mA fuse (not a 'shunt'), which will blow under fault conditions (not simply a ground loop which in audio systems introduce noise rather than shock hazard, generally). This is a bad idea as once the earth path is disconnected by the fuse blowing the only other path for current to flow to earth is via the player... –  Fergus Mar 5 at 3:44

My experience is that single coil pickups are quite susceptible to this, but humbuckers much less so or not at all.

I have seen the same effect vary from guitar to guitar.. bass with single coil buzzed horribly. Strat with single coils less so. Same player, same amp (yes, I know.. bass through guitar setup .. there were reasons)

So I see that this can vary from guitar to guitar. Strats often have a bit of tin foil mounted (glued) on the inside of the scratch plate to help with this issue. As for earthing the strings : variable - sometimes yes, sometimes no, but mostly they are earthed in my own experience.

My Les Paul in the same setup as above didn't buzz at all. Humbuckers .. clue's in the name ;-)

I'd conclude that this isn't really "normal" for a Les Paul (sorry!).

Things you could check ..

  • Is your lead well earthed ? Some 'look' like they are (ie all soldered up properly) but something breaks down in the shilding in the lead and they become noisy, sometimes giving strange results.
  • Does any other guitar buzz like that through the same setup ?
  • IYou say you just built the guitar- is it all wired up properly ? (though I bet you've checked that) I'm at the edge of my knowledge here but I gather it's possible to set what looks like one humbucker up as just two single coils so that you don't get the hum cancelling effect. That would be the wiring between the two coils of the pickup itelf
  • If you set it to the middle position, (both pickups), does the hum go away ? If so this hints at the pickups behaving more like single coils than humbuckers.

Hope this helps.

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