After some jamming, I noticed my guitar makes a clicky sound every time I place my finger on some open string (it can only be heard with an amp connected, maybe it's too soft for it to be heard unplugged). I first figured it was hitting itself with some fret, probably because of bad neck calibration, but it keeps clicking even if I touch it very gently and almost not move it at all. All I could find over the internet related to this is sounds that are produced while lifting the finger, not placing it...

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    What happens if you use your right hand to lightly touch some of the strings and keep it there, and then you touch and release different strings with your left? Does it still "click"? If it doesn't click when you do that, then it's probably a pop caused by completing a ground circuit with your body. That's normal. If it does click when you do that then I don't know what it is. Jun 19 '19 at 21:54
  • Agree that it's almost certainly a ground connection. Either that or you're Magneto in disguise. Jun 20 '19 at 13:54
  • @ToddWilcox you seem to be right... I'd never have thought the strings were conductive (they obviously are tho) nor they would be connected to anything (that I still don't know where)
    – Iaka Noe
    Jun 20 '19 at 17:37
  • @CarlWitthoft probably the latter
    – Iaka Noe
    Jun 20 '19 at 17:37
  • @ToddWilcox oh! you're talking about static! so my only fix would be to have an antistatic bracelet or wear shoes?
    – Iaka Noe
    Jun 20 '19 at 17:39

Some introductory facts:

  • The strings of an electric guitar must conduct electricity. That's actually how they work. When the string vibrates over the pickup, a very small current flows in the strings at the same frequency that the string is vibrating. Then that current causes another current in the pickups, again at the same frequency, and the pickup current is amplified to make the sound you hear. If you put nylon strings (that don't conduct electricity) on an electric guitar, you won't hear anything when you play it.
  • The strings of an electric guitar are grounded via the bridge. The bridge conducts electricity and inside the body of the guitar there should be a wire that connects the bridge to the ground - usually the casing of one of the pots. This is to reduce the effects of the strings basically acting like radio antennas.

So, with that in mind, here's what's happening:

  • When you're not touching any of the grounded parts of the guitar (bridge, strings, jack plate, possibly other parts), the strings are basically radio antennas. They are picking up radio waves that are then picked up by the pickups and amplified. Usually these radio waves are fairly weak and most (but not all) of the current induced by the radio waves bleeds off to ground and is not amplified.
  • When you touch any grounded part of the guitar, the current induced in the strings by the radio waves partly bleeds to ground and partly bleeds into your body. This dramatically reduces the amount of current that is left in the strings and picked up by the pickups. So touching a grounded part of the guitar reduces the (usually quiet) buzz that you get with an electric guitar.
  • Right at the moment of touching it, you're basically closing a circuit. Usually when circuits close there's a very rapid change in the flow of current, and that change is so rapid that it sends a pulse through the relevant conductors. That pulse is picked up by the pickups and is amplified as a pop.
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    "When the string vibrates over the pickup, a very small current flows in the strings at the same frequency that the string is vibrating." There's a magnetic field around the string, which induces a current in the pickup coil, but there's no current running through the string, afaik. Jun 20 '19 at 20:51
  • @YourUncleBob Where does the magnetic field around the string come from? It is created by the current in the string. A conductor moving through a magnetic field has a current induced in it. The initial magnetic field is generated by the magnetic pole pieces of the pickup. Then when the string moves through that field, a current is induced in the string. Jun 20 '19 at 23:38
  • As I understand it, the pole pieces, which are permanent magnets, have their magnetic field distorted by the moving strings. The movement of the magnetic field relative to the coil, induces a current in the coil. (As you say, touching the strings grounds them, so any current running through the strings would disappear via your body.) See e.g. reilandercustomguitar.com/… Jun 20 '19 at 23:52
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    The current in the string is caused by the movement of the string past the magnet. I think that's why YUB is objecting to the original wording. We don't want people to think that the string-current is causing the signal in the pickup. Jun 21 '19 at 13:04
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    Uncle Bob is right. “Strings...must conduct electricity. That's actually how they work” – this bit is not true. They work by way of being ferromagnetic (iron and/or nickel). Aluminium or bronze strings wouldn't work, whereas nylon strings with powdered ferrite would (albeit badly), despite being nonconductive. — Perhaps aluminium strings would have a bit of eddy current induced in them as well, but at least for the thin treble strings it would be completely insignificant – the cross-section is too small. There is no current induced along the string, this can be seen by a symmetry argument. Jun 22 '19 at 13:21

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