#1
Hi, I have a question on grounding technique. I tried for the first time using the vintage gibson-style wire with the grounding braid on the outside. My guitar is not the noisiest I've had but it isn't quiet, and so there seems to be a grounding issue somewhere. I've been thinking, since the ground shield is exposed on all these wires, it could be touching any number of things (and for sure is touching cables that are routed along with it) and this would be causing grounding loops.

What are some best practices on wiring with this type of wire or should I just forget it and go back go using regular stranded shield wire (or even unshielded?)

-RJ
#2
When you say you wired a guitar with it, do you mean that all the wire in the guitar is that braided stuff? A picture or description of exactly what is used where might help.

Is the cavity shielded? I've seen a few noisy instruments where using shielded wire was done as a substitute for shielding the entire cavity, with varied but usually subpar results.

If the cavity is shielded, It's certainly not impossible that the braided wire is causing some of your issue, especially if it really is used for the entire instrument. Usually that braided wire is just for a couple of connections like the pickup leads and the run to the output jack. Most of the stuff in between isn't usually (and probably shouldn't be, for reasons you seem to understand) done with the braided stuff. If you have the cavity shielded properly there's just no reason to invite ground loops by shielding the individual short connections.
#3
Thanks for your reply

I did some more debugging on this, and funny you should mention, but I actually ended up shielding the cavities tonight (it is a Dean ML 79 with the switch up way far away from the cavity), and it seems to have reduced the noise by 20%, but it is still about twice as noisy as any of my other guitars, including some that do not have shielded cavities, so it is quite noisy still.

My setup is I have a Pegasus and Sentient pickup set, which are 4-wire configuration non-braided. each has an individual volume pot which they are wired straight to. then, the outputs from those volume pots are connected to braided cable. The braid is soldered onto the back of the pot., as well as the chassis ground and the earth end of each pickup for their respective pot. The two braided cables go up through the pickup cavities to the switch, and a third braided cable comes back down from the switch's output. All three braids are soldered onto the switch.

The output braided cable comes back to the main control cavity and the braid is soldered onto the body of the tone pot. the cap is soldered straight from the wiper contact to the body, and another braided cable from the output jack is soldered straight onto the body. Both leads from the jack and the switch are soldered onto the correct end pin of the tone pot.

I think I'm going to order some shielded and additionally insulated wire and just rewire the whole thing. But, I still don't have a great formula for how to deal with the fact that the now shielded cavity connects the grounds of all the pots, and they are also connected by this wiring setup.

I think the real issue here is that those three braided cables run almost the entire length of an explorer-like body guitar and back, so there is a huge AM-antenna sized loop in the wiring. I think a possible solution might be to use 4-conductor pickup wire so that all three leads are inside the same shielding, but that's probably a project for another day. soldering all these connections really takes it out of me

-R
#4
I should also mention, that unlike in other cases of hum that I've dealt with in the past, this hum does not seem to change whatsoever if you touch the jack, the strings, any ground or for that matter hot lead.

In the past, issues like this I have solved by making sure grounds were properly connected; I had another dean that just had a crappy bridge that didn't conduct well enough so the strings were effectively not grounded, and replacing the bridge did the trick. That doesn't seem to be the case with this guitar :/

Whatever it is, I believe it to be an antenna-like EM pickup... or maybe the pickups themselves are not bucking that hum as I would think they are.

-R
#5
Quote by runfrodorun

I think I'm going to order some shielded and additionally insulated wire and just rewire the whole thing. But, I still don't have a great formula for how to deal with the fact that the now shielded cavity connects the grounds of all the pots, and they are also connected by this wiring setup.

I think the real issue here is that those three braided cables run almost the entire length of an explorer-like body guitar and back, so there is a huge AM-antenna sized loop in the wiring. I think a possible solution might be to use 4-conductor pickup wire so that all three leads are inside the same shielding, but that's probably a project for another day. soldering all these connections really takes it out of me

-R

I agree. I don't see any need for that many redundant ground connections. If the cavity is shielded, I would use plain, standard unshielded wire. There's no reason to add all that extra length of shield wire to an already shielded control cavity. For the existing braided wire you could use shrink-wrap or just a bit of electrical tape where you think there might be an issue. The pickup wiring is usually ok, but it sounds like you have way more wiring than most guitars.

Just ground everything once, to a 'star ground' on the back of one of the pots. Then ground that pot to the bridge, and the shielding to the star ground. The star ground is a pretty clean way of making sure you don't have a huge mess of grounds referencing other grounds referencing others. It sounds like you have that going on.
#6
To clarify, should I ground pots that are on the same shielding to each other, or just leave it with the shield connection and call it a day?

Thanks!
#7
"Same shielding" equals grounded, and if you only have one path to ground for each component, you won't have any ground loops. So, double check that the connection to the shielding is good and just leave it.

So that means that if all your pots are connected to the shielding, that you will use that shielding as the star ground instead of the back of that one pot. Just connect the shielding to the output jack ground in that case.

That's a pretty robust setup, and you shouldn't be getting much noise with it. I assume you know what you're doing with the shielding, and that you don't have any breaks in continuity there.
#8
Roc8995Sorry haven't been on in a while.

I have an additional question regarding this issue--- what are people's thoughts on running multiple braided cables to a different cavity for a pickup selector switch (think vintage les paul style). All those wires ground shields are obviously touching. In order to avoid ground loops, my thoughts were either to individually electrical tape each wire, or better yet, to tape all three leads together so that they are effectively continuous everywhere.

Gibson has obviously run these wires to the cavity together for years. Is it really so much of a problem that they touch? Or perhaps it matters that much less when dealing with low-gain vintage scenarios and we start caring with high gain amps?

-R
#9
That's a good question. Ideally I guess there's some merit to total isolation (electrical tape) but I wouldn't want to sit there wrapping and snaking all those wires, and I doubt there'd be much or any difference when you were all done. How much would we expect the ground to differ over the couple of inches where the shields weren't touching? Probably none. A lower effort approach might be total homogenization - that is, just turn the three braids into one larger continuously connected shield, perhaps by twisting them just a little bit to make sure they're in contact the whole time. That would at least make it easier to snake them through the route to the selector switch. The conventional way of tying the shields together is to solder the whole bunch together at the switch cavity - I think that's a fine solution, again because there just isn't much in the way of ground loop that's likely to occur in the shielding between the two cavities. It's not like there's a significant signal or change in ground reference there.

I don't think it's a likely location for significant noise, and as you say Gibson has been doing it for quite a while with no apparent issues. Certainly there's always room for improvement, but isolating the wires is probably not going to change anything.

Some interesting discussion of shielding/grounding here:
http://www.mylespaul.com/forums/showthread.php?t=122705