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grounding? something?

Discussion in 'Basses [BG]' started by Sharp, Sep 11, 2002.


  1. Sharp

    Sharp

    Jan 27, 2002
    Oakland
    Artists Relations, KMI
    im not sure why, but my bass only stops this terrible hum when i touch the strings, or bridge or tuning bachines or control plate... all those things are metal but yall probly knew that. im not sure what it really is, some grounding issue probably, but i cant figger it out, any help'd be appreciated.

    -Sharp
     
  2. MorganM

    MorganM

    Dec 11, 1999
    Sounds like grounding to me.
    Make sure the bridge is grounded to the output jack and all the pots, pickups, etc.
     
  3. geshel

    geshel

    Oct 2, 2001
    Seattle
    The fact that it stops when he touches the strings indicates that the bridge is grounded.

    It's a shielding issue. How is the control cavity of your bass shielded? (conductive paint? copper foil? neither?) What kind of pickups does it have?
     
  4. DigMe

    DigMe

    Aug 10, 2002
    Waco, TX
    It could be a shielding issue but it's not automatically a shielding issue. My Fodera is very well shielded and it's grounded. However sometimes I play places that have insufficient grounding at the outlet and the same buzzing occurs with me when I remove my fingers from the strings. I take a good power strip and always do my damndest to try to get to another outlet when this happens but sometimes you just gotta live with it. Sometimes it gets solved by bypassing whatever extension cord or power strip us being used and plugging my Monster power strip straight into the wall.

    Sharp - Does this always happen no matter where you are or what you plug into? If so then that is indicative of a shielding issue. Otherwise maybe not.

    brad cook
     
  5. Sharp

    Sharp

    Jan 27, 2002
    Oakland
    Artists Relations, KMI
    yeah, i think you're probably right, i hadnt noticed it until i started playing in a different room. the socet isnt grounded, so i have a 3 prong to 2 prong adapter. would this do it?

    the pickups are fender 60s CS jazz **plug** i like them alot, they sound awesome wven though there is the single coil hum. go buy some.**end plug**

    -Sharp
     
  6. Sharp

    Sharp

    Jan 27, 2002
    Oakland
    Artists Relations, KMI
    after experimentation:

    1- the bass still buzzes when no 3 prong to 2 prong adapter i used.

    2- the bass does buzz on another amp.

    3- i have only 1 cord right now (my cat bites through cord) and it is lookin pretty trashed.

    4- other bass does hum with questionable cable

    final thoughts: can the cord be causing all this buzzing anguish? What should i look for in the cord that could cause this? if i get a new cord, whatqualities should i look for?

    -Sharp
     
  7. geshel

    geshel

    Oct 2, 2001
    Seattle
    What I meant was, the fact that it stops when he touches the strings indicates that the bridge is grounded. :) If the bridge weren't connected it would have no effect.

    Sorry for the confusion - grounding/shielding definitely do go hand in hand. I think pickups with exposed polepieces are more susceptible to this type of noise.

    My bass has always been dead quiet, then a week ago I played a new place and everything was buzzing, including my bass (though not as bad). Think it was a nearby neon sign.

    I have to take a moment here and warn you that "cheater plugs" are dangerous.
     
  8. geshel

    geshel

    Oct 2, 2001
    Seattle
    Definitely. The cord is shielded and needs to stay that way. Sounds like yours isn't (is any of the braid showing through the insulation?). Did you try your bass with a better cord? I think for now, "intact" should be at the top of your list of things to look for. :)
     
  9. Sharp

    Sharp

    Jan 27, 2002
    Oakland
    Artists Relations, KMI
    why? i hadnt heard this before-
     
  10. embellisher

    embellisher Holy Ghost filled Bass Player Staff Member Supporting Member

    Because when you use a cheater plug, you have no ground. If the outlet or the amp is faulty, and you become grounded by touching something that is grounded, you can have 20 amps of 110 volt ac coursing through your body. Very unpleasant at best, and fatal at worst.
     
  11. geshel

    geshel

    Oct 2, 2001
    Seattle
    Because it's possible that there's a short inside the equipment and the chassis is hot. If that is the case, and you plug it into a grounded outlet, the breaker will trip. If you plug it into a 2-prong outlet, the chassis may stay hot, and shock someone who touches it. Or anything touching it, namely the strings on your guitar (since we've already shown that they are "grounded" :) ).

    If your buddy has his amp plugged in to a good ground, and touches your amp with one hand while touching his strings with the other, he's going to get a really nasty shock. (some people have the misconception that being personally grounded is good. It's not. 110V AC through you and your rubber-soled shoes into dry ground is not fun, but not nearly as bad as straight from one hand to the other to ground.).

    There are a lot of "ifs" and "mays" here, but I don't take those chances.
     
  12. Sharp

    Sharp

    Jan 27, 2002
    Oakland
    Artists Relations, KMI
    zzapp:eek:
    well... im sold, no more cheater plugs for me... actually, ive been electricuted twice, but not due to cheater plugs. once when i was first starting on bass an i played barefoot on the grass of the lawn at the hotel we were stayin at. the second time was because i (absent-mindedly) went to change the lightbulb of the stand light in the pit of a musical, forgot to unplug it, an touched both leads. no fun, but nothing serious, i was alright, just... well... shocked:cool: .
     
  13. tyson

    tyson

    Feb 9, 2000
    Dallas, TX
    just remember. a defibrillator will actually stop your heart and then your body's natural pulses attempt to take over and make your heart beat normally again...of course that's a larger, more controlled pulse.

    anyway, i just pieced together a p-bass (with all non-fender componets) and i'm having the same issue, buzzing until i touch the string, bridge, jack rim, or control. within the instrument everything is wired and grounded correclty but i don't know about my apartment outlet. the pickups are Seymour Duncan SPB-1 Vintage. i think that along with the fact that i currently do not have any shielding in the cavity are the cause. if i get the buzz after i apply good copper shielding then i'll blame the outlets. is any other shielding better then copper? what about lead? :eek:
     
  14. KB

    KB

    Jan 13, 2000
    Chapel Hill, NC
    I get the same type of grounding issue with my G&L L2000 (1982 model) that has basically no shielding and big hot MFD pickups. It seems to get worse in the winter (dry/cold?) and almost goes away in the summer (humid/hot). I have switched cables, etc. and it still is there. I just assumed it was from no shielding.

    I used an ohm-meter and checked all the continuity of the grounds and found no problems.
    I guess it is something to just have to live with???
    Unless anyone else has ideas on how to get rid of the noise.

    -KB
     
  15. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    I had exactly that problem on a P, about six months ago.
    I resoldered the ground wire form the bridge, and no further problems.
    Is that a hint, or what?

    Actually, I asked about the reason in setup, under the headline "Why wire the wires". Find that, and know why Geshel is wrong.....

    Of course, shielding is an issue that also can result in hum.
     
  16. geshel

    geshel

    Oct 2, 2001
    Seattle
    It'd be nice if you could just come out and say why I'm wrong. If I'm wrong because you think that the safety issues with grounding the strings are worth decreasing buzz, well I don't agree. Shield the cavity first. I also don't know how grounding the bridge will have much effect when you're not touchig the strings. In fact, it shouldn't have any.

    Edit: I read the thread about grounding the bridge and the whole capacitor thing. I don't quite see it. The examples given to back up the theory (capacitor tuning in radios) are off base.

    Here's an easy way for me at least, to shoot down that theory: supposedly it takes you touching the strings to make the capacitor that causes the buzz. But, 99% of the time, people have buzz problems without even touching the guitar. It's something else.
     
  17. Suburban

    Suburban

    Jan 15, 2001
    lower mid Sweden
    Sorry Geshel, didn't mean to trodd on your toes. Must have forgotten some douzen wink-smileys.

    Safety: there is a major risk in connecting the strings to the ground. IF something goes really wrong in the line, you may end up fried.
    Agreed.
    Could be solved by using a thin wire between bridge and ground, thus working as fuse as well as ground wire. Or introducing a small fuse to the circuit.

    Capacitance: the capacitance is built up by two electrical leaders at a distance (connected to circuit or not). If you connect one end to a circuit, and not the other, the effect is as having a huge resistor between the non-connected and ground. Which causes hum.
    When you touch the strings, you connect it to ground via your body, and the hum disappears - the circuit is closed.

    If you combine the "unaffected capacity hum" with the antenna funktions of all cables in there, you may have some heavy buzz'n'hum!

    My recommendation is to do both a good cavity shielding, and a "fuse ground" to the bridge. And also have a peek on how the pups and pup cabes are shielded....
     
  18. Taylor Livingston

    Taylor Livingston Supporting Member Commercial User

    Dec 25, 2002
    Louisiana, US
    Owner, Iron Ether Electronics
    one of my basses makes terrible noise, and i was going to shield it. i got instructions from guitarnuts.com, but they are really time- and money-consuming, and are getting me to do things i don't need at this moment (i need to shield the cavity before a solo bass performance at an art opening in two days), and the instructions are set up in a way that i can't pick what i need to do to shield the bass from the other stuff.

    if i just cover the cavity in foil or shielding paint or tape, is that it? or do i have to bother with wiring (the instructions i have mention running the ground to the shielding)? sorry to bring up an old thread and kind of derail it, but you all seem to know about this topic, and i didn't want to start a new thread.
     
  19. geshel

    geshel

    Oct 2, 2001
    Seattle
    For the shielding to be effective, you'll probably have to connect the shield from the pickup wires to it electrically. Though honestly, I'd find painting/lining the cavity to be much more time consuming than soldering a wire.
     
  20. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Try this - solder a 50pf capacitor across the output jack - it works!