Why ground the bridge and stop tail?

[RayL]

Greetings, I'm confused so I'm going to attempt to explain my Knowledge of guitars and please correct me if I'm mistaken.
Guitar pickups pick up interferences and hum and so do the shielding of the guitar, without a ground, the noises have nowhere to go and cause hums and noises. So it makes sense to me to have the shieldings and pickup grounded so that the noises ground itself to the earth.
What I don't understand is, why ground the bridge and tail piece? Because to my knowledge, a properly grounded amp should provide the ground to direct the noises from the pick up and shielding. I am aware of that a grounded bridge will make it possible for the player to ground the guitar himself or herself with an ungrounded amp hence making the ungrounded amp quieter when touching the strings. However doesn't it also creates danger for the player to get shocks since it's incredibly easy to make contact with the bridge or strings and making the player himself an active ground?
So my problem is, why ground the bridge, when in a PROPERLY grounded circuit, it doesnt help with noise (?) and only creates danger for the player in case he makes contact with an inproperly grounded equipment such as a mic system.
P.S. Note that I'm assuming that in a properly grounded situation, the hum would be gone even without the player touching the strings, would it? I don't think I ever had a pleasure to play in this situation, as every time I play the hum doesn't go away unless I make contact and ground it myself.
Thx, sry if some of the wording seem confusing, it's not easy to explain, ask me if ur unsure of what I meant.

 

[Mark_F]

The bridge and tailpiece need to be grounded to the guitars ground (back of pots and the ground on the jack) to stop interference from any electrical potential (think kinda like static) in the strings interfering with the pickup and creating noise.

If they were kept seperate from the ground loop in the guitar, static and other things builds up creating hum and stuff through the pickups, that tends to change when you touch the strings (ie ground them to yourself). As this noise change can't be controlled, it has no use (so it ain't like feedback where some folk can use it in a way they want), so noone wants it, and the best way to get rid of it is to ground to the rest of the guitar.

Maybe i made that look overcomplicated and waffled on, but that's basically it.

 

[RayL]

The bridge and tailpiece need to be grounded to the guitars ground (back of pots and the ground on the jack) to stop interference from any electrical potential (think kinda like static) in the strings interfering with the pickup and creating noise.

If they were kept seperate from the ground loop in the guitar, static and other things builds up creating hum and stuff through the pickups, that tends to change when you touch the strings (ie ground them to yourself). As this noise change can't be controlled, it has no use (so it ain't like feedback where some folk can use it in a way they want), so noone wants it, and the best way to get rid of it is to ground to the rest of the guitar.

Maybe i made that look overcomplicated and waffled on, but that's basically it.

Wow thx, now I understand, so basically strings and bridges do stack noises with statics so they need to be grounded, cool thx. Don't plastic generate statics fairly easy as well? Then can pick guard cause hum? Sorry if this seems like a silly question

Also, let's say I have a well grounded guitar with humbuckers plugged into a properly working amp which is plugged into a properly grounded and clean power source, with no electric interferences, can I still have some hum?

In other words, can I assume that eveytime the hums goes away when I touch the strings means the something is wrong with the grounding? Or is it just that even when all things are set properly and working properly, I am still going to get some hum? I'm saying this cause I have plugged my guitar which is grounded into a dozen different amps and outlets yet I still find touching the strings quitentens the hums, wheather by a bit or a lot.

I was never in a situation which touching the strings doesn't help to quiaten the hum by a bit. Of course there are certain amps and on certain outlets that make minimal hum, but its still always there. Is that normal? Or is it that in the ideal situation, the hum should be non existent even when the strings are not touched? Bet I'm generally talking about distorted.
Just trying to this striaght as I have been confused about this for quite long, thx

 

[KenG]

The grounding on the stringsd isn't done for noise, it's done for safety to prevent the strings from reaching any other potential voltage as they are touched by human hands and (strings) are therefore exposed much like the chassis of applicances and powere tools. The assumption for this to work of course is that the operator (player in this case) does not come into contact with any other improperly grounded equipment. If this happens the strings now provide a potential path to ground thru the operator when they touch a poorly grounded piece of equipment.
If you think you make come into this kind of situation, placing a resistor inseries between the Tailpiece ground wire and where it gets soldered to the pot body can limit the current to less than fatal levels.

 

[chrisuk]

The reason a guitar is quieter when you are in contact with the strings is that the guitar is actually grounding YOU.

Otherwise the human body acts as an antenna for noise. There is a post about this somewhere from one of the wiring gurus on the site.

 

[RayL]

The grounding on the stringsd isn't done for noise, it's done for safety to prevent the strings from reaching any other potential voltage as they are touched by human hands and (strings) are therefore exposed much like the chassis of applicances and powere tools. The assumption for this to work of course is that the operator (player in this case) does not come into contact with any other improperly grounded equipment. If this happens the strings now provide a potential path to ground thru the operator when they touch a poorly grounded piece of equipment.
If you think you make come into this kind of situation, placing a resistor inseries between the Tailpiece ground wire and where it gets soldered to the pot body can limit the current to less than fatal levels.

Sorry but I don't understand, if the strings are grounded, they basically make no physical contact with the circuit, then how can they be dangerous? Cheers

The reason a guitar is quieter when you are in contact with the strings is that the guitar is actually grounding YOU.

So in a situation which the guitar is already grounded properly, me touching the strings would still help to provide ground and hence making it even quieter?

 

[Tone deaf]

The reason a guitar is quieter when you are in contact with the strings is that the guitar is actually grounding YOU.

Otherwise the human body acts as an antenna for noise. There is a post about this somewhere from one of the wiring gurus on the site.

We'z got multiple complicated thingies goin' on over hea.

Tune your clock radio to your favorite station and let go. It is likely that it won't sound as good when you were holding it. This is because when you are holding it, you are (as pointed out above) acting as the antenna.

As KenG pointed out, 'safety' isn't just a slogan around here. Your amp is plugged into the wall (110-120V for most of us (220v+ for others)) which will provide enough current to straighten your hair (if you have any).

You have two grounding issues and I am in no way capable of providing the science behind either. One is the creation of ground loops which cause undesirable noise in circuits and the other is conducting sufficient current to ruin one's day. I believe (one of you EEs please correct me) that it is possible to properly ground an axe while still leaving the possibility for ground loops to exist.