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Ground the bridge or not?

Discussion in 'Pickups & Electronics [BG]' started by KramerDon, Nov 5, 2013.


  1. I'm building a 5 string and have a pair of Nordstrand fatstack pickups that I'd like to use passively.I've read that grounding the bridge is dangerous and causes a shock hazard,and I've read the bridge has to be grounded to prevent hum.
    Now I'm just confused,if anyone could help me understand the pro's and con's I'd be very grateful!
     
  2. Rockin Mike

    Rockin Mike

    May 27, 2011
    I'm also curious. I've heard it both ways.
     
  3. funnyfingers

    funnyfingers

    Nov 27, 2005
    I've heard of people getting shocked when not using a grounding plug. I remember playing with an amp with something wrong and I would get a tiny zap if I didn't wear shoes in the basement. Not sure if the plug or outlet didn't have a ground. Also heard of a rockstar electrocuted playing barefoot with a bad ground. Not sure if all pickups do this, but the one bass that I had buzzing was because the connection to the bridge was not good. Connected it to ground and no buzzing.
     
  4. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    If your electronics are not grounded you will get a hum, it might be constant or it might actually get louder when you touch any metal/string/bridge. You wouldn't want to use that bass to record with unless you like hum on your album.

    Most manufacturers run a ground wire from under the bridge into the tone control cavity so you do not see it unlike the ground straps of yesteryear.
     
  5. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    I thought grounding the strings coupled them to the coils of the pickups electronically to produce better sound?
     
  6. This is extreme paranoia. You want your bridge grounded, unless you love hum.
     
  7. P Town

    P Town

    Dec 7, 2011
    Ground the bridge. No safety hazard, unless connected to unsafe, defective equipment.
     
  8. Joedog

    Joedog

    Jan 28, 2010
    Pensacola FL
    Hmmmm...my 4 string bridge is not grounded (passive J pups, preamp w/bypass to run totally passive if so desired) and is as SILENT as any bass I've ever played: dead quiet at all times. I've recorded w/it multiple times. Yes I'm sure it's not grounded...I built it.
     
  9. Technotitclan

    Technotitclan Lurking TB from work

    Mar 1, 2012
    Rochester, NY
    The risk is with venue wiring, not your bass. Some venues, not all, have terrible wiring with very bad grounding.

    Ground your bridge. You gain nothing from not doing it other than hum.
     
  10. megafiddle

    megafiddle

    May 25, 2011
    When someone asks, "should I ground the bridge", they are usually asking if the bridge
    should be connected to circuit common. Whether it is actually grounded or not is another
    matter. So one has to be careful with the terminology.

    If your bridge is "connected" and your amp is grounded properly, then the cable shield,
    the strings, and you (if you're touching them) are all grounded. In that case, the danger
    is from coming in contact with something that is not grounded. An ungrounded mic might
    have a voltage on it, and your grounded strings provide a path, through you, to ground.
    By itself though, your equipment would be safe.

    If your bridge is "connected" and your amp is not grounded properly, then the cable shield,
    the strings, and you (if you're touching them) might all have a voltage present on them. You
    may or may not feel a tingle or shock. But the danger now is if you also come in contact with
    an actual ground (not that a mild shock or tingle should ever be considered harmless).

    If the bridge is not "connected", then the strings and bridge are safe, but the above still applies
    to metal controls, output jack bushing and nut, metal plug shell.

    If the bass is shielded well enough, you can have a quiet bass with unconnected bridge. That's
    assuming the amp ground is good.
    But stock basses with incomplete or no shielding will typically hum in that case, with the hum
    even getting worse when you touch the strings. Such basses should have connected bridges
    for that reason. The zero volt ground potential on you and the strings reduce the hum.

    -
     
  11. uOpt

    uOpt

    Jul 21, 2008
    Boston, MA, USA
    If you have other complete shielding you don't need the grounded strings, which is really all about abusing your body as a shield.

    The risk of shock is there if you have the strings grounded. Funnyfingers, you need to be more careful with what you post, especially when we are talking about life-threatening issues. I could elaborate on which risk goes up and down but I've done so many times.


    I have put up a reference about electromagnetic and eletrostatic interference and what do do about it in electric guitars and basses here:
    http://www.seymourduncan.com/forum/...terference-and-fighting-it-in-guitar-and-bass
     
  12. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    OK, I've read it. You do not understand what electromagnetic interference is. You have it confused with magnetic field interference. Common shielding techniques are very effective against electromagnetic interference, and electric field interference, and high frequency magnetic interference. Conductive shields do not work well against low frequency magnetic fields unless they are prohibitively thick which is another way to say heavy. Mu metal is not remarkably heavy, in fact thin and light mu metal sheets are fairly effective against low frequency magnetic fields. I have no idea how expensive it is but I doubt you want to use it on a bass guitar because you need to let low frequency magnetic fields into your pickups if they are to function.

    There is no such thing as "ground". You can call it mass or anything you like but it does not exist. Or rather you can pick any point, anywhere in the universe and call it ground if you like. Your definition is a good as anyone else's. Ground is a polite and useful fiction so I will use it below but there is absolutely no point in getting overly precise about what is and is not ground.

    A grounded bridge and strings are only slightly more dangerous than an ungrounded bridge and strings. The reason for this is that there are already several pieces of exposed metal on your bass and amp cord that if hot will kill you instantly. The notion that it is safe to play in such conditions as long as your bridge and strings remain ungrounded is utterly false. If your venue's wiring puts the hot side of the AC mains on your bass ground then it is also on your amp cable ground and all kinds of exposed metal pieces on your amp and everything else connected to your system. You are going to die if you try to play under such conditions. Thankfully they are exceedingly rare.

    Roger Sadowsky has said his very well shielded basses will still hum under some circumstances unless the human being holding the bass is grounded. He even recommends against using tapewound strings because of this. I have a couple of well shielded basses that pick up interference from an electronic drum kit. I have an unshielded bass that picks it up at the same level. They all have hum canceling pickups of one kind or another. The only thing that kills the noise is touching the grounded strings. I tend to agree with Roger on this one, shielding is not necessarily enough. As far as your body being a shield, I don't think so. It is far, far too incomplete to be effective. It is more likely that grounding your body works because your body picks up so much noise.
     
  13. uOpt

    uOpt

    Jul 21, 2008
    Boston, MA, USA
    Before I address the rest of your post, do you have a more direct quote for this?

    I have a hunch there are a couple more conditions at work here. Because if you have humbuckers you can shield completely and whatever your body is picking up won't enter it.
     
  14. bassbenj

    bassbenj

    Aug 11, 2009
    No you can't shield pickups (humbuckers or otherswise) completely. You can shield a pickup cavity but the tops of the pickups are always sticking out. Now it IS possible for the manufacturer to provide shielding inside the pickups (it can change the tone) but typically manufacturers scrimp. many bass makers (even for $1000 basses) often have much less than adequate shielding and pickup makers still slap open coils inside plastic (no shielding) covers.

    The bottom line is grounded strings DO help eliminate hum. Generally speaking the ONLY pickups that work well with ungrounded strings are active pickups (like active EMGs). They advertise the ungrounded strings as a safety feature (which is is) But virtually all other makers ground strings to reduce hum.

    The problem is that if knobs and jack get "hot" with a poor ground and you touch them, you get shocked and pull your hand away and you live. But if you are gripping strings with one hand, when you get shocked your muscles tighten from the electricity and you can't let go. You die. Quite a few classic cases of accidents like these. But nevertheless active pickups are still uncommon enough that most all basses have grounded strings.

    A ground fault indicator is your friend at a gig.
     
  15. kohntarkosz

    kohntarkosz Banned

    Oct 29, 2013
    Edinburgh - Scotland
    I've seen a (Dan Erlewine?) trick of running a cap and resistor in parallel on the ground wire to your bridge. That way, if your amp decides to give you some electricity you will be ok, at the cost of introducting a wee bit more noise into the signal. I think EMG pickups do not require grounding to the bridge, but I'm not sure why that is.
     
  16. So I guess I need to drill a path from under the bridge to the control cavity.I am a Michigan licensed electrician and I replace 277V ballasts hot almost daily yet I've never gotten anywhere near the severity of shocks as an industrial,commercial electrician as I did when on the road in the late 70's early 80's when I would sometimes get nearly blackout shocks from touching my mike.(The lips are not a good place to get shocked either!!!)
    Thanks everyone for the feedback!!
     
  17. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars

    First of all, there is no way the venue could put the hot side of their AC current to your amps ground with out either tripping a breaker or starting a fire.
    Secondly 99.9% of the time a healthy person will survive a 120 volt shock.

    The whole nonsense about the bridge ground abusing your body, and that it puts you in danger to be shocked and killed is ridiculous. The wire going to the bridge is usually between 22 and 24awg. That wire would burn in two before it could deliver enough current to kill a person with a healthy heart. If you are that nervous about being electrocuted by your bridge ground, use a strand of solder as your bridge ground. If any current starts flowing to that it will melt, acting like an instant fuze. Personally I am not worried about it.
     
  18. uOpt

    uOpt

    Jul 21, 2008
    Boston, MA, USA
    My point was specifically about an instrument that has humbuckers (see the text you quoted) and has a shield around all the hot wires.

    You don't need any additional shielding around humbuckers since -well- they cancel hum, and that cancellation is good both for electrostatic and electromagnetic interference.

    The situation is entirely different with single coils. You can shield all you want, they will pick up interference. (unless you put them into MU metal but then the whole exercise is kind of pointless)
     
  19. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Ground the bridge.
     
  20. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    All I can tell you is that you will find it in the Strings forum in one of the many, many threads about tapewounds.

    On edit:

    Ok, it was easier to find than I thought by just doing a Google forum search on Sadowsky AND tapewound. The thread I was thinking of is found here and another one that Roger hisself started is here.

    So if you really hate the idea of grounding your bridge and strings and remain convinced it converts your bass into a death trap (and you will see that Roger disagrees with that too) you could use an antistatic electronics assembly wrist strap (I believe Radio Shack and the like sell them) to ground yourself to your bass through a 1 Meg Ohm resistor. This is considered safe around the normal power mains voltages by all national authorities as far as I know and in another thread which I am entirely too lazy to search for someone reported that it is effective against body induced hum. Best of both worlds as long as you don't mind wearing a wrist strap (and you will see that Roger has an alternative for that too....) and if you find that it kills your hum problems. A sample size of one is all we have right now on that and one report of success with hum is not statistically significant. I do have an antistatic wrist strap I could take to church to see if it works there, the only place I have to ground myself to eliminate hum. But that won't happen next until Dec 22 and even then the Christmas configuration of the stage often has me on the opposite side from the drum kit and I don't get the hum unless I am right next to the drums. Plus I have to REMEMBER TO DO IT.... As I mentioned in that thread as long as you use uncoated, conductive strings you could also put that 1 Meg safety resistor in series with your ground wire. Now you are at no risk at all from touching your grounded strings.
     

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