JamesW Posted June 28, 2004 Report Share Posted June 28, 2004 Can anyone enlighten me, is it essential to connect an earth or ground wire to the bridge? And is this just to prevent mains hum, or is it for safety reasons (i.e. prevention of electric shock if the amp/mains supply is faulty) ? Quote Link to comment Share on other sites More sharing options...
Biohazard Posted June 28, 2004 Report Share Posted June 28, 2004 It is also a safety device. So I would not consider missing out this wire. Quote Link to comment Share on other sites More sharing options...
JamesW Posted June 28, 2004 Author Report Share Posted June 28, 2004 I'm still confused though - if the bridge and strings are not connected to anything, then if the earth wire of the mains became live, then you wouldn't get electrocuted. If the bridge and strings were earthed, then you would. I've also read somewhere that inserting a 1megohm resistor between the brige and the earth is a good idea to prevent electric shock. Quote Link to comment Share on other sites More sharing options...
fidgec94 Posted June 28, 2004 Report Share Posted June 28, 2004 But if you touch a live string, wouldnt that complete the circuit? I see no advantage to deliberately leave the bridge ground wire off, its clearly something that is important. As per the guitarnuts website, it says that modern amps arent usually a problem but if you hook up to some dodgy wiring or an old valve amp, you could potentially have a problem. Meh, i have a basic understanding... Quote Link to comment Share on other sites More sharing options...
Biohazard Posted June 28, 2004 Report Share Posted June 28, 2004 Connecting the bridge to earth does not mean that it gives a greater risk. Earth means that any current will take the earth wire to earth rather than through you. Or something like that. Basically, put the bridge earth wire in. Quote Link to comment Share on other sites More sharing options...
JamesW Posted June 28, 2004 Author Report Share Posted June 28, 2004 But if the mains circuit was dodgy, e.g. the earth wire was switched with the live or neutral by mistake (this has happened), or an amp was dodgy, then the common earth of the amp and guitar would all be live. Now if the strings and bridge were not connected to the common earth at all, then surely this is the ultimate safe option? Although humming would be present, so perhaps the high value resistor would help, although I wonder what value of resistor could protect you from 240V. Quote Link to comment Share on other sites More sharing options...
Biohazard Posted June 28, 2004 Report Share Posted June 28, 2004 I'm only quoting advice by everyone else. You can choose not to put that wire in if you want to. It's up to you. I personally am putting in a bridge earth connection on my new guitar when it arrives. But it's up to you what you want to do with yours. Quote Link to comment Share on other sites More sharing options...
Black Mariah Posted June 28, 2004 Report Share Posted June 28, 2004 If you use passive pickups, you have to have a bridge ground. Because, and isn't this fun, YOU are the earth. Yes, that's right. This is why you usually notice an increase in noise when you take you hands off the strings. This is, in fact, potentially dangerous. If your guitar/amp and, for example, the microphone you are singing into are different polarities (or is it the same polarity? Guh, can't remember) and you put your lips on the mic while singing and playing... *ZAP* You could get nailed by just a few volts all the way up to whatever voltage the power in the building is. There some very easy ways to keep this from happening. Use one of those foam windscreens on your mics, don't sing at all, or use active pickups. One of the advantages of active pickups such as EMG's is that they're internally grounded and don't require you acting as a human lightning rod to work. Before you start playing, take your guitar and hold the string close to the mic. If you see sparks, run. Use your amps polarity switch, if it has one, and be careful. Quote Link to comment Share on other sites More sharing options...
Biohazard Posted June 28, 2004 Report Share Posted June 28, 2004 Good advice Black Mariah, but for those using passives, the bridge earth connection is what should be done, right? Quote Link to comment Share on other sites More sharing options...
JamesW Posted June 28, 2004 Author Report Share Posted June 28, 2004 But if the strings and bridge are NOT connected to earth or to anything at all, then they can never become live, even if the pickups DO become live (because the guitar is plugged into a dodgy amp etc)..surely? I don't mean to go on about it, or start an argument, just want to understand the whole think properly. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 28, 2004 Report Share Posted June 28, 2004 Bridge grounding is simply done to enhance the shielding of the guitar electronics - if you disconnect it while using passive pickups, you will see a notable increase in noise. If you can live with it, leave it disconnected - if not, either use active pickups or use a grounded bridge. The aforementioned Guitar Nuts site recommends grounding the bridge through a .33µf, 400V cap to protect against DC from a failing tube amp, but even that won't help you if the mains are wired incorrectly. Quote Link to comment Share on other sites More sharing options...
truerussian558 Posted June 28, 2004 Report Share Posted June 28, 2004 the above advice (not lovekraft) was all wrong, grounding the strings, brings a chance of getting shocked, this is a rare appearance, and probably will never happen to you if you play only at home or gig at one place, but if you tour a lot, and gig at many places, the chances of a badly grounded socket incereasem especially if its an outdoor concert, also so does the possibility of tube amp failure, if you groun d the bridge, and because of faulty wiring in the socket, the ground becomes live, you will have a verry nasty and potentially deadly shock when you play the guitar, but then again not grounding the bridge/strings, increases hum about 2 fold, do the best thing to do if you are worried is eaither to wire it through a cap, or what in my oppi9nion is better, wiring it through a fuse. also black mariah's answer is also bullshit, you are not the ground, actually you are the one being grounded, i think theres something on thios in the guitar nuts page listed by lovekraft. of course there is a chance of you being the ground, but how aoften are you playing with your feet on a steel block, or in a puddle of water, so that you do turn into a ground also the only other time youd do become the ground, is if the voltage is lethal, as in you have a few hundred volts going through your body that can jump to the nearest equipment (microphone etc), or throuigh the ground if its strong enough. edit: here is the guitar nuts page on shock hazards Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 28, 2004 Report Share Posted June 28, 2004 Wow! truerussian558, you really could have phrased that a bit more diplomatically, but I'm not your daddy, so I'm not here to spank you. As for the electric shock issue, the only thing I will say is that while it's probably not a problem in your house, any travelling musican who doesn't own an outlet polarity and ground fault checker is putting his life in the hands of every apprentice and unlicensed electrician that ever did a cheap wiring job on the side for a venue owner! Y'all be careful out there! Quote Link to comment Share on other sites More sharing options...
JamesW Posted June 28, 2004 Author Report Share Posted June 28, 2004 That guitarnuts site is quite good. It reccomends that you "disconnect the bridge ground wire on your guitar or use a small (about .02uf) capacitor shunted by a large (about 220k) resistor to isolate the bridge from the rest of the ground. Note that this may significantly increase the amount of hum you experience. Also note that this is only a partial fix – the jack plate and some other exposed metal parts (including metal volume and tone knobs) of your guitar and amplifier will still be potentially lethal." So not having a bridge connection seems like a good idea. I made my current guitar and forgot to put a wire in, so I've never had one. I do experience hum, though not much though. The guitarnuts site seems to think that the cap and resistor method would still produce hum, the way they've worded the above..which woudl defeat the object.....? It probably works though. truerussian558, that's what i thought. The hum is not so bad on my guitar and only when I let go of the strings. I like the fuse idea. what fuse rating would you recommend? Not a mains fuse...a low voltage one, say 10V? Are they available? So no bridge grounding or usa a fuse or cap, and no exposed metal parts on the guitar (use plastic pickup covers and volume knobs)..and you should be safe. Just don't touch the mic Quote Link to comment Share on other sites More sharing options...
truerussian558 Posted June 28, 2004 Report Share Posted June 28, 2004 if your worried about the pots going live, you could always put the fuse, or cap on the wire going to ground on the plug, but if the fuse goes, so does your guitar, so maybe a cap there might also not hurt, i think a fuse is better for the bridge since the hum doesnt increase, though if there is a shock it suddenly get s a lot louder because the fuse breaks, im not an expert in values and such but ive read enough on shielding to give some advice, (mainly from the guitar nuts site ) so i think you should try to get the lowest voltage fuse, i think ten volts will do, hell even 110 volts would do, especially if its the amp that fails and puts a few hundred volts dc on the ground, ouch..., Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 28, 2004 Report Share Posted June 28, 2004 It's a good idea (the fuse), with one major downside - you've got to find a fuse that blows faster than your central nervous system. It'll blow before you catch fire, but it doesn't take long to send the heart into fibrillation (I'm not a doctor, but I've seen one on TV ), so the fuse would have to be ultra-fast to protect the player. Quote Link to comment Share on other sites More sharing options...
truerussian558 Posted June 28, 2004 Report Share Posted June 28, 2004 still better then an outright shock though thiugh you should try to find some ultra fast fuses, or a fuse that is very low value so the enormous voltae will burn it out quickly but the idea is to make it so the shock isnt fatal, you will still get a shock but it wont be as deadly, also a fuse and or cap doesnt substitute checking the mains wiring at any location you play at, just to be sure. Quote Link to comment Share on other sites More sharing options...
Biohazard Posted June 28, 2004 Report Share Posted June 28, 2004 LOL, no metal parts. OMG, i'm buggered then with my new guitar's aluminium finish. Aluminium on the front back and sides of the body. Well, I think I won't last long out there. Although, it's rare that these fatal accidents happen though isn't it. Quote Link to comment Share on other sites More sharing options...
cacibi Posted June 28, 2004 Report Share Posted June 28, 2004 Isn't there a built-in bridge ground on some pickups? I know that tele bridge pups are usually grounded to the copper base plate which, in turn, is connected to the bridge via the mounting screws. Quote Link to comment Share on other sites More sharing options...
Black Mariah Posted June 29, 2004 Report Share Posted June 29, 2004 the above advice (not lovekraft) was all wrong, grounding the strings, brings a chance of getting shocked, this is a rare appearance, and probably will never happen to you if you play only at home or gig at one place, but if you tour a lot, and gig at many places, the chances of a badly grounded socket incereasem especially if its an outdoor concert, also so does the possibility of tube amp failure, if you groun d the bridge, and because of faulty wiring in the socket, the ground becomes live, you will have a verry nasty and potentially deadly shock when you play the guitar, but then again not grounding the bridge/strings, increases hum about 2 fold, do the best thing to do if you are worried is eaither to wire it through a cap, or what in my oppi9nion is better, wiring it through a fuse. also black mariah's answer is also bullshit, you are not the ground, actually you are the one being grounded, i think theres something on thios in the guitar nuts page listed by lovekraft. of course there is a chance of you being the ground, but how aoften are you playing with your feet on a steel block, or in a puddle of water, so that you do turn into a ground also the only other time youd do become the ground, is if the voltage is lethal, as in you have a few hundred volts going through your body that can jump to the nearest equipment (microphone etc), or throuigh the ground if its strong enough. edit: here is the guitar nuts page on shock hazards My answer was not bullshit. You'd know this if you actually read the article you linked, or even read your own comments. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 29, 2004 Report Share Posted June 29, 2004 Just get a wireless - it eliminates shock hazards from your guitar, so all you have to worry about is your amp, the microphones, the light switches, etc. Quote Link to comment Share on other sites More sharing options...
truerussian558 Posted June 29, 2004 Report Share Posted June 29, 2004 i ment the part about you being the ground is the bullshit, i beleive its explained, in one of the myths part of the guitar nutys page, everything else was correct, sorry i should have been more clear Quote Link to comment Share on other sites More sharing options...
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