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Hum when not touching strings?

Discussion in 'Pickups & Electronics [BG]' started by Electricblue, May 17, 2011.


  1. Electricblue

    Electricblue

    Feb 1, 2011
    Norfolk
    Ok, I guess this is normal. I've checked the bridge connections and my wiring is stellar.

    Is this the same "grounding" problem that can cause shocks, or is it just an amp thing for if your tube amp malfunctions etc?

    I'm fine with the noise being there, but its just a case of whether its dangerous?

    :D
     
  2. bassbenj

    bassbenj

    Aug 11, 2009
    If the hum goes away when you touch the strings that means the strings (bridge) is grounded. And that is both standard and dangerous. The idea is that if your strings are grounded and you are grabbing them when you play and then you touch a "hot" circuit such as a PA mic with an improper ground, you can get electrocuted! The electricity goes from the bad mic, through your heart, out through your arms and hands to the strings and to ground. Serious business. More than a few have died this way!

    This is the reason for active pickups and floating (ungrounded) strings and bridges. But few basses have this.

    So the deal is most basses have grounded strings and it's up to YOU to check the grounds and wiring on the gear to make sure nothing is accidentally "hot". You can buy cheap but effective ground testers at hardware stores you just plug in and read the lights to insure venue wiring is properly done. If the tester shows otherwise, refuse to play until it's fixed!

    As for the hum, hum that goes away when you touch strings says that your shielding is bad or non-existent or not grounded. I'm glad you can live with the hum, most of us can't. It just needs looked into. At most all it needs is some copper foil and a bit of time. But the shielding doesn't change any safety issue which are separate.
     
  3. Electricblue

    Electricblue

    Feb 1, 2011
    Norfolk
    Is it worth putting a SPST between the bridge and ground? Would this make my bass a bit safer?

    I dont really notice the hum, just the faint pop when I touch the strings and let go.
     
  4. CaptainSir

    CaptainSir

    May 12, 2009
    Conyers, Ga
    on top of grounding hum/pop you might be hearing. if you are using single coil pickups then you could also be hearing 60 cycle hum which is completely normal and adding copper foil or metal based paint to the inside of your guitar can reduce or maybe eliminate your problem.
     
  5. Electricblue

    Electricblue

    Feb 1, 2011
    Norfolk
    I am using a squier jazz-bass with both pickups wired in series, with one volume control.
     
  6. CaptainSir

    CaptainSir

    May 12, 2009
    Conyers, Ga
    what you are hearing is really normal. if you can deal with the hum i say keep on keeping on. if not there are a few options you can look into, 1.) overhaul the electronics on your bass. pretty easy to do if you are somewhat handy will keep the cost down if you do it yourself. just swap out the pickups with fender american made noiseless or your choice of upgraded J style pickups. use new wire most people perfer insulated cloth wire.
    2nd option would be to upgrade to a different bass
    like i said what your hearing is normal. many people learn to deal with it. one thing that can help is to roll your tone back slightly and play at a lower volume on your bass and use amp to generate more volume. like i said the easiest fix but most costly is to upgrade your bass
    like always thats my 2 cents


     
  7. Electricblue

    Electricblue

    Feb 1, 2011
    Norfolk
    I dont have a tone control. Just one volume and my series pickups which are always on and therefore dont hum :)
     
  8. bassbenj

    bassbenj

    Aug 11, 2009
    If you find no hum or other weird effects when the bridge is not grounded (you can just lift the bridge wire from ground inside the cavity) then Just leave the strings ungrounded. That does make the bass safer. But not perfect. Point is you are usually grabbing the strings and if you touch a hot source (like an ungrounded mic) the electricity tightens your grip on the strings and you can't let go. You die. Hence ungrounded strings are safer. But remember that the SAME thing can happen from ANY grounded metal be it the control plate, metal knobs or plug or jack body. BEST is to test venue electrical grounds FIRST!
     
  9. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    I had this same problem with my bass, and the hum went away after I did the complete copper foil shielding.

    I am not sure, but I think that the strings have to be grounded for the pickups to work properly, which is why they all are, as far as I have seen. I don't know why the makers would go to the extra trouble to ground the strings if it wasn't necessary.
     
  10. No, they'll still work, but whatever hum is present won't be eliminated when touching strings.
    When the bridge is grounded, your body capacitance reduces/cancels the 60Hz hum.
     

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