Grounding

[silvertonessuckbutigotone]

Hi guys, I know about grounding (I think). What I don't know is how it works. I know it saves feedback, I also know it keeps from shocking you in high humidity. I also know/think/have heard that if you have a grounding malfunction it could shock you pretty bad if your bridge is grounded. I'm kind of curious to know how grounding works. Why it does what it does. I think this would be a good way for me to expand my knowledge not only in building electronics but also designing them.

[lovekraft]

Actually, grounding does none of those things - the only reason we have to even consider it is that a good grounding scheme will reduce overall noise, usually in conjunction with shielding. And while youcan get shocked from touching a grounded bridge, there is nothing you can miswire in your guitar that can cause you to get shocked. Unless there is a fault in either your amp or the mains supply (or some other piece of line-powered equipment you are in contact with), you never need to worry about your guitar shocking you. For more info on shielding, grounding and minimizing shock hazards, check out John Atchley's articles over at Guitar Nuts.

Edited February 1, 2005 by lovekraft

[silvertonessuckbutigotone]

I did a search on google for "how-gorunding-works" and looked at a few pages, and all of them say it is a wire connected to a metal post driven into the earth. I'm pretty sure that this isn't the case on a guitar. So... how is this related to a guitar bridge or an input/output jack? Also, I'm just curious, I don't have any specific questions.

[Southpa]

I think the primary function for a grounding system is to pick up any stray voltage differences that might occur between contact points, including static electricity you might be carrying or other outside electrical influences you might touch, eg. another guitar, an amp, microphone etc. Its a safety system designed to channel voltage differences to an outlet that is more "electrically attractive" than your body. Each metal component should be hooked up in the grounding system to a common point. I usually choose the volume pot then run a wire from there to the ground lug of the output jack. This is better than having the ground path going thru your body, ie. electric shock on the extreme side:D .

An ungrounded bridge results in humming when fingers are not touching the strings. This is electrical interaction between your strings and those electromagnets we call pickups. When you touch the strings your body completes the path to ground rather than the string to bridge contact points. Of course, the amount of current you receive is extremely small but that annoying hum will remain unless an exit path has been made. But in the event that you DO receive a solid jolt from somewhere a grounded bridge/system will save your life.

Edited February 1, 2005 by Southpa

[westhemann]

and all of them say it is a wire connected to a metal post driven into the earth. I'm pretty sure that this isn't the case on a guitar.

actually ,it is the case on a guitar.common ground is grounded to input jack,which is then transferred to the amp ground,which is grounded to your house electrical system,which is grounded to the 6 foot(usually) copper rod or copper cables which are buried in the ground.

if you don'tbelieve me,go outside to your electric meter and look for a copper wire running from the meter to the ground and look at what it is clamped to

capische?

[thomasteven]

If your volume pot wasn't grounded you would always have a constant volume, no matter where the knob was. when you turn the volume knob, it shunts more or less of the signal to ground which gives you the differences in volume.

[silvertonessuckbutigotone]

hmm thats interesting. What happens to the ground prong when you have an adapter that changes a 3 prong into a 2 prong? JW.

So basically from what I've gathered is the ground absorbs anything extra and cancels it from the circuitry to minimize extra crap?

[truerussian558]

if your ground doesnt work the volume pot will still work, like a rheostat (variable resistor) the resistance between the signal and the amp will increase and thus more of a voltage drop, so the guitar would drive the amp with a lower level signal when the volume is turned down and a higher level signal when the volume is turned up, (though if the lug is still atached to ground (but not grounded to earth) it will probably buzz like crazy)

When you use a 3 prong to 2 prong adapter nothing happens to the ground it just ends up hanging in the air (which could be potentially dangerous), in reality your supposed to take a single wire and drive it to the ground prong of a 3 pronged outlet (instead of a long extension cord for the whole plug), or grounding it directly to a rod in the ground ( like when you are usuing an outdoor generator), or sometimes efven grounding to a pipe in the vicinity will work, (though it might be nasty if the wire suddenly goes live)

In effect that is all that grounding in the guitar does. it shunts all the unneeded voltages (like emi emmited by computer monitors) and shunting them to neutral voltage source (ground), so that they cannot bleed into the circuit, or interfere with the signal.

Edited February 2, 2005 by truerussian558

[silvertonessuckbutigotone]

So if I wanted to, I could (very primitive I know, but hey!) add a prong to my outlet by putting a socket that would accept the third prong into the outlet and then connecting that socket to a copper post driven into the soil in my backyard or does it need to be really deep? I don't plan on doing this in the near future because my house has a 3 hole outlet in it, but just for theory?

[orgmorg]

The neutral wire in household current ( the white one ) is, or is supposed to be connected to the ground spike also. The sefety ground ( green or bare ) is there as a more direct route to earth ( ground spike ) in case a hot wire comes loose. That is why it is connected to every metal enclosure.

Since AC current reverses direction 60 times per second ( 50 in some parts of the world ) , the amp doesn't really care which wire is hot and which one is neutral, so older plugs could be plugged in either way. This was fine until you stepped up to a mike on a PA that was plugged in opposite the way your amp was.

[westhemann]

This was fine until you stepped up to a mike on a PA that was plugged in opposite the way your amp was.

ouch

[silvertonessuckbutigotone]

So by grounding the sheilding in a guitar control cavity, what you are doing is having it accept any interference, but send it to the ground? Why is conductive sheilding still used even when it's not being grounded?

And the reason we ground a bridge is so that if it picks up any intereference it wont send it to the pickups or the control cavity? So instead of cancelling intereference it accepts it and gets it out of where we don't want it?

And thats why when grounding is bad the hum goes away when you touch the strings, it's like a substitute for grounding.

And in schematics of footswitches etc. the symbol for ground in the in/out jacks are in reality just connected to eachother?

I think I'm beginning to put the peices together. Or maybe I'm dead wrong and really slow...

...why couldn't I just have sticked with PLAYING a guitar and not playing WITH it? lol.

[Dugz Ink]

So by grounding the sheilding in a guitar control cavity, what you are doing is having it accept any interference, but send it to the ground?

Good shielding is nothing more than a solid antenna that "catches" all of the RFI/EMI before it can get to your low-voltage wiring and controls. However, you have to do something with that RFI/EMI, otherwise the shielding will collect more RFI/EMI (than the little components) and surround/saturate the components with RFI/EMI. So, you connect the shielding to a "ground"... or a connection that eventually leads to a post in the ground.

Do NOT "chain" the ground wires in your guitar. Let's say you're going to ground your bridge; if you attach that "ground" wire to the casing around you pots, then you are adding the RFI/EMI that is picked up by the bridge to the casing around the pots, which can actually lead to the bridge's RFI/EMI bleeding into pot. It's better to run the wire from your bridge to the final "ground" point on your jack... along with the "ground" wire for the shielding, and the "ground" wire for your pots, and so on.

That's what we call a "star ground"... and, yes, the grounds in the schematics are connected... unless they specifically say otherwise. (That's not very common with consumer-grade equipment... I can't even think of an example.)

BTW: If your equipment does NOT have a three-prong cable, then it's not grounded to the wall outlet. For instance, the little pre-amps and guitar effects that use the external power converters (the ugly boxes that plug into wall outlets) are not grounded to the wall; they pass the "ground" through the audio cable to the next component.

D~s

[silvertonessuckbutigotone]

wow, I finally sort of got something figured out lol. with the help of 13 replys. Thanks for all your guys' posts it really helped me understand why I'm grounding the bridge and stuff. Thanks again.