Guys im losing my mind with this grounding issue

[DrNomis_44]

A good thing to invest in if you're going to build more electric guitars is a good digital multimeter, you can pick up a reasonably priced one from most electronics parts stores, very handy when it comes to troubleshooting the wiring in electric guitars.

[dingobass]

Personally I always connect up the backs of my pot casings, but I also cut a plastic guard out of milk bottle for each and every pot to make sure the lugs can't contact the shielding. It's basically a wierd shaped washer that corresponds to the underside profile of the pot, with a hole for the shaft to stick through. I'm happy to take a little extra time connecting the pot casings if it means I dont have to troubleshoot shorts with the lugs!

cheers,
Gav.

Hey Gav, no need to join the casings if you have shielded.
Have heard a few old timer Luthiers say you can actually cause problems by over earthing!? (Your thoughts on this, Weirdy?)
I do like the plastic washer idea, especially on recessed pots like Woks pointed out.
My thoughts are the less heat you put into a pot the better

[stan]

don't know about too much earthing.
In this case "earth" is more of a common return path.
You can get ground loop issues, I guess... but isn't that more of an AC thing? as such more amp related... Our guitars are generally passive.
And copper linings,etc., are for RF shielding, which itself needs to be grounded, but does form part of the grounding...
My head hurts

[dingobass]

The same questions are running around my head too, Stan..

[Rabbitz]

It seems to me that some people are confusing "earth loop" or "ground loop" with the concept of "multiple earth paths".

Having multiple paths to ground is not, on its own, a bad thing.

The issue of "ground loops" arises when there are paths between grounds of different potentials. That is to say when different grounds are sitting at different voltage levels in respect to each other. This can occur when elements of a PA might be powered off different circuits or phases. Typically should these grounds be joined (looped) then it can introduce noise - usually seen as a 50 Hz hum.

In the case of a guitar, it SHOULD only have one ground reference - coming from the shield of the guitar lead. Therefore each of the earth paths within the body of the guitar should all be at the same potential - that of the guitar lead ground. For the purists, yes, the voltage drop over the wiring and high resistance joints etc can introduce a potential difference but as the wires are so short the drop can be safely ignored and if you have a HR joint there are other problems to solve first.

So if all the ground points, wires, shields etc are at the same potential, i.e. all go back to the single ground reference, then no voltage can flow between them so the multiple paths will not generate ground loop noise.

I hope that makes sense.

[keloooe]

Fair point Rabbitz, but guitars (normally) should have two though, one at the jack and another at the bridge?
Loops shouldn't really be common in guitars as the wiring always ends up at the jack, correct?

[Rabbitz]

Fair point Rabbitz, but guitars (normally) should have two though, one at the jack and another at the bridge?
Loops shouldn't really be common in guitars as the wiring always ends up at the jack, correct?

I am talking about electrical grounds - the bridge is just another earthing point. It does not provide a return path to a different earth potential.

The only path to electrical ground *should* be via the output jack ground.

If you have a path to a different electrical ground via the bridge and by extension the strings I don't want to be standing in that spot holding that guitar - who knows what stray voltage you might experience...

I would expect that it is important to make sure the bridge is grounded (I haven't really thought about this) is that the string are probably a pretty good antenna, and may have voltage (and therefore noise) induced into them - grounding them will overcome this.

I am more than happy to be corrected on any of this. I have experience in electronics/radio/electrical but not a lot of experience of guitar electrics per se. (I've plugged plenty of 'em in, and repaired a few that had electricals come to grief, but I've never looked at the electrics in detail...