Shielded cable for guitar wiring

[RockinProf]

I’m working away on my ridiculously overbuilt covid guitar. Because I can’t play/jam/rehearse with others I’ve had the time to really dissect every component I’m putting in to this one and why I’m doing it. One of my few remaining decisions is on if I go with shielded or twisted paired wire for the longer runs where the components have a ground. In this case I’m using a single 500K pot, a Freeway toggle switch and an output jack. No tone pot. Here I’d gave two coax shielded cables or twisted pairs…. so decisions, decisions. Any thoughts on the topic if one uses very low capacitance cable?

 

[AdrianSD]

Test both options? Shielding s known to raise the cable capacitance, you're correct. If you're concerned with RF/EMI you can shield the pickups (less effective if they're uncovered) and pots cavities (quite effective), ground the shields and use unshielded wire for connectivity.

 

[beaubrummels]

IME interference it most likely to come in via the pickup coils, which have thousands of turns of wire in a coil, which is basically an omni-directional antenna. The couple inches of connecting leads from component to component have been much less of a concern for me. Just shielding the control cavity and having grounds properly connected should cover most noise issues.

 

[GuitarStv]

If your pickup cavity is shielded, there's no point running shielded wiring. All the tests I've done have showed this. It doesn't hurt, but doesn't help either.

 

[RockinProf]

What I didn’t mention is that I’m attempting to skip shielding the body as I’m getting a pro paint job and don’t want to aggravate the painter by having to deal with the shielding or shield after the fact and have paint compatibility issues. By going shielded wire I’m thinking I should be able to suppress noise. With ~6-8 inches of shielded cable (I have 28pF/ft cable) I shouldn’t have issues… I think. or am I off on this?

 

[GuitarStv]

What I didn’t mention is that I’m attempting to skip shielding the body as I’m getting a pro paint job and don’t want to aggravate the painter by having to deal with the shielding or shield after the fact and have paint compatibility issues. By going shielded wire I’m thinking I should be able to suppress noise. With ~6-8 inches of shielded cable (I have 28pF/ft cable) I shouldn’t have issues… I think. or am I off on this?

In that case, I'd go with the shielded wire. (Actually, I'd shield the cavity with copper tape after getting everything painted . . . but I use shielded wire on my Epi Dot because there's do damned way to shield inside the f-hole. )

 

[Drak]

You're doing the mental herky-jerky here, just take a breath and relax.

Get your paint job done first.
When you get it back, use shielding tape and double-layer tape all your cavities.
Tape is much easier to install and offers more shielding than paint.
And run a piece of tape between the various cavities to connect them.
Or use a piece of wire and slap a piece of tape over it to make the connection.

I've been building guitars for over 25 years, I fully shield every single guitar I've ever built.
Shielding is one of the very, very last things to be done.
It's part of the final assembly process, and comes in at the very end.
By the time I'm shielding, I'm going to have a new guitar that night.
Before I move on past the shielding, I check all cavities for continuity between them with an ohm meter.
To make sure everything is connected to each other.

Forget about twisted pairs and shielded cable.
I have a roll of shielded cable I've had for over 30 years.
I never, ever use any of it inside a guitar unless I'm wiring a hollowbody 335 kind of thing.

I mean, do what you want, but your plan would fly against what I consider absolutely routine assembly procedures.

 

[Artie]

I have a roll of shielded cable I've had for over 30 years.
I never, ever use any of it inside a guitar unless I'm wiring a hollowbody 335 kind of thing.

I do like to use shielded wire to run the 3-way in an LP-style guitar, but that's more for the convenience of the single bundle rather than the shield aspect per se.

 

[ErikH]

My old Frankenstrat has zero shielding in the body. The underside of the pickguard has the thin foil tape but that is it. I simply use insulated wire and twist them together from the volume pot to the output jack. No noise from it. It's very quiet. If I was using single-coils I might do more shielding and have in the past.

 

[ThreeChordWonder]

IME interference it most likely to come in via the pickup coils, which have thousands of turns of wire in a coil, which is basically an omni-directional antenna. The couple inches of connecting leads from component to component have been much less of a concern for me. Just shielding the control cavity and having grounds properly connected should cover most noise issues.

What he said.

And if you like, you can always twist together the wires from the pickups and /or to the output jack. I do that anyway, but more to keep them matched together than over RF concerns.

 

[NegativeEase]

Twisted Pair won't do much without a common mode rejection/differential circuit to cast of the inducted difference.

Shield the Cavity and under the pick guard if you have one and make sure it is connected to the drain/ground to the 1/4 jack and you are good.

 

[RockinProf]

I have my solution. I went with just one pot and a toggle. I took a couple of old Schaller strap lock acrylic boxes and shielded those, placed the pot in one and the toggle in the other, used 28pF/ft shielded cable and paint ed the boxes to match the paint job. Yes way over the top, but the pot and switch are in total faraday cages, the wires are all shielded and with super low capacitance. Lockdown did have the cool result of a totally uncompromising guitar. When it’s completely done I’ll post pictures with gut shots when it’s done.

 

[beaubrummels]

How did you shield the acrylic boxes? You were able to ground the shield?