Why wire the Ground to the Bridge?

[koshersteel]

howdy,
 
  I see that ground is wired to the bridge in all the wiring diagrams but I don't understand why. It seems unnecessary or even dangerous to me. Can someone please illuminate me as to why this is necessary?

 

[jackthehack]

How could it possibly be dangerous? If you do not ground the bridge you will likely get a "hum" when at rest, unless you ground it yourself by touching the strings/bridge.

 

[GoDrex]

How could it possibly be dangerous? If you do not ground the bridge you will likely get a "hum" when at rest, unless you ground it yourself by touching the strings/bridge.

some active pickup circuits are actually safer - sine they're not grounded to the strings. This way you can't get shocked by a mic, if the polority happens to be opposite. I guess this is less common these days. I can remember getting some shocks. I once touched the strings on my friend's bass while holding my guitar and got a nice shock.

 

[Orpheo]

good question. why can't the groundwire go to the amp's earth?

 

[DiMitriR33]

in japan we have no earth conductor in the sockets, just hot and neutral, now technically neutral is earth but there is not always a way to tell which is which. also some stuff only has 2 conductor power cables even in the states. may also have something to do with something in the way the amp is wired, CB could answer that i haven't had too many chances to poke around inside tube amps. 

 

[koshersteel]

I guess (part of) what I'm not understanding is why ground to the bridge which I rest my hand on instead of grounding to a ground plate located in the cavity?

 

[Xplorervoodoo]

There was a link a while back - can't remember now, cause I'm at work... - but it was a link to a webpage full of wiring tips and tricks.  The page in question had a schematic for wiring in a resistor between the ground wire and the bridge.  That way you can have the noiseless application that grouding to the bridge grants, and you'd also have protection against any kind of polarity shock, because the resistor would reduce the amperage to you.

 

[jackthehack]

I guess (part of) what I'm not understanding is why ground to the bridge which I rest my hand on instead of grounding to a ground plate located in the cavity?

You aren't always touching the strings/bridge and it will hum if you aren't. At volume in a venue it can be pretty loud/annoying.

"good question. why can't the groundwire go to the amp's earth? "

ALL the grounds in your guitar's circuit(s) go to amp's ground through ground wire in your cable.

I can't speak for active electronics, don't use them, consult your documentation.

 

[Orpheo]

I guess (part of) what I'm not understanding is why ground to the bridge which I rest my hand on instead of grounding to a ground plate located in the cavity?

You aren't always touching the strings/bridge and it will hum if you aren't. At volume in a venue it can be pretty loud/annoying.

"good question. why can't the groundwire go to the amp's earth? "

ALL the grounds in your guitar's circuit(s) go to amp's ground through ground wire in your cable.

I can't speak for active electronics, don't use them, consult your documentation.

why does it hum when I dont touch the metal parts?

 

[jackthehack]

"why does it hum when I dont touch the metal parts? "

If you are getting a hum when NOT touching the metal parts on your guitar you probably have a faulty ground connection between the bridge and the ground - out side of your output jack.

Don't know what kind of bridge you're using, but if a tremolo with the claw that Warmoth ships with them you need to scrape the finish off the top of the claw where you make the grounding connection to get a good one. If you are using a flatmount Tele/Strat bridge you need to scrape some of the chrome/black/gold finish back to bare metal to get a good ground connection. If using a TOM bridge, did you strip enough wire off and can you see it through the hole in the stud when you pull the screw out of the stud?

Check the solder point where you connected the bridge wire to a grounding point in the circuit and ensure you have continuity to the output jack from there..

 

[Orpheo]

"why does it hum when I dont touch the metal parts? "

If you are getting a hum when NOT touching the metal parts on your guitar you probably have a faulty ground connection between the bridge and the ground - out side of your output jack.

Don't know what kind of bridge you're using, but if a tremolo with the claw that Warmoth ships with them you need to scrape the finish off the top of the claw where you make the grounding connection to get a good one. If you are using a flatmount Tele/Strat bridge you need to scrape some of the chrome/black/gold finish back to bare metal to get a good ground connection. If using a TOM bridge, did you strip enough wire off and can you see it through the hole in the stud when you pull the screw out of the stud?

Check the solder point where you connected the bridge wire to a grounding point in the circuit and ensure you have continuity to the output jack from there..

what I check is if I get a signal from the potbacks up until the bridge, and with all of them, I get a little 'beeep' with my multimeter.

but:where does this hum come from?

 

[GoDrex]

4) When installing EMG Active Pickups, DO NOT connect
the bridge ground wire. This wire is usually soldered
to a volume or tone control casing and goes to the
bridge. This wire grounds the strings and uses them
and your body as a shield against hum and buzz. It
also creates a shock hazard. EMG Pickups are
shielded internally and DO NOT require string
grounding. This greatly reduces the possibility of
reverse polarity shock from microphones and other
equipment

 

[DocNrock]

4) When installing EMG Active Pickups, DO NOT connect
the bridge ground wire. This wire is usually soldered
to a volume or tone control casing and goes to the
bridge. This wire grounds the strings and uses them
and your body as a shield against hum and buzz. It
also creates a shock hazard. EMG Pickups are
shielded internally and DO NOT require string
grounding. This greatly reduces the possibility of
reverse polarity shock from microphones and other
equipment

This is for actives, not passives.  On EMGs, the (-) of the battery goes to the ground on the output jack.

 

[GoDrex]

Yeah Doc - did you happen to read my post above that one? I know I'm dumb but come on. It says Active in the first sentence too. Gee-whiz!

 

[DocNrock]

Yeah Doc - did you happen to read my post above that one? I know I'm dumb but come on. It says Active in the first sentence too. Gee-whiz!

I can be dense too.  I don't get it.  :icon_scratch:

What I did not see in your post is that the (-) of the battery connects to the ground of the jack.  That is what makes the difference...I think... :tard:

 

[jackthehack]

"why does it hum when I dont touch the metal parts? "

If you are getting a hum when NOT touching the metal parts on your guitar you probably have a faulty ground connection between the bridge and the ground - out side of your output jack.

Don't know what kind of bridge you're using, but if a tremolo with the claw that Warmoth ships with them you need to scrape the finish off the top of the claw where you make the grounding connection to get a good one. If you are using a flatmount Tele/Strat bridge you need to scrape some of the chrome/black/gold finish back to bare metal to get a good ground connection. If using a TOM bridge, did you strip enough wire off and can you see it through the hole in the stud when you pull the screw out of the stud?

Check the solder point where you connected the bridge wire to a grounding point in the circuit and ensure you have continuity to the output jack from there..

what I check is if I get a signal from the potbacks up until the bridge, and with all of them, I get a little 'beeep' with my multimeter.

but:where does this hum come from?

Check and see if you get a continuity beep from bridge to ground on output jack.

 

[joeh]

There was a link a while back - can't remember now, cause I'm at work... - but it was a link to a webpage full of wiring tips and tricks.  The page in question had a schematic for wiring in a resistor between the ground wire and the bridge.  That way you can have the noiseless application that grouding to the bridge grants, and you'd also have protection against any kind of polarity shock, because the resistor would reduce the amperage to you.

Do you mean this page: http://www.guitarnuts.com/technical/electrical/safety/index.php

It mentions to put both a resistor and a capacitor - but only as a "case-by-case" needed situation, as this does introduce more string noise, and you will still get shocked if you touch any other grounded metal parts on guitar.

 

[GoDrex]

Yeah Doc - did you happen to read MY POST ABOVE THAT ONE? I know I'm dumb but come on. It says Active in the first sentence too. Gee-whiz!

In a previous post I was talking about how actives were safer - because jack was saying how could grounding the bridge be dangerous - and then he wrote something about not using actives so I found the EMG insstallation info and posted it here.

 

[Xplorervoodoo]

There was a link a while back - can't remember now, cause I'm at work... - but it was a link to a webpage full of wiring tips and tricks.  The page in question had a schematic for wiring in a resistor between the ground wire and the bridge.  That way you can have the noiseless application that grouding to the bridge grants, and you'd also have protection against any kind of polarity shock, because the resistor would reduce the amperage to you.

Do you mean this page: http://www.guitarnuts.com/technical/electrical/safety/index.php

It mentions to put both a resistor and a capacitor - but only as a "case-by-case" needed situation, as this does introduce more string noise, and you will still get shocked if you touch any other grounded metal parts on guitar.

Nope, found it, now that I'm home:

http://alexplorer.net/guitar/mods/shock.html

 

[jackthehack]

There was a link a while back - can't remember now, cause I'm at work... - but it was a link to a webpage full of wiring tips and tricks.  The page in question had a schematic for wiring in a resistor between the ground wire and the bridge.  That way you can have the noiseless application that grouding to the bridge grants, and you'd also have protection against any kind of polarity shock, because the resistor would reduce the amperage to you.

Do you mean this page: http://www.guitarnuts.com/technical/electrical/safety/index.php

It mentions to put both a resistor and a capacitor - but only as a "case-by-case" needed situation, as this does introduce more string noise, and you will still get shocked if you touch any other grounded metal parts on guitar.

Nope, found it, now that I'm home:

http://alexplorer.net/guitar/mods/shock.html

The little 250K resistor shown in that picture wouldn't do fudge all but arc out, you'd need a huge 250v+ step down resistor.

I've been around forever and seen everything and never heard of an amp shorting back voltage sufficient to be considered dangerous to a guitar. Although anything's possible, if the cord didn't melt at 117 volts or better the 22 gauge or so wire connecting your output jack should blow like a fuse before you get hit with voltage of that level.

Science experiment: Take a piece of guitar wiring, typically around 22 gauge, about 6 inches long; bare both ends about an inch, bend in a U and hold in insulated grip pliers and plug it into a 117 volt wall socket and see what happens.