Shielded 4-conductor Wire

[NQbass7]

Looked around for an answer to this, but not finding anything.

So I'm working on a Les Paul, but I'm doing things slightly different with the wiring. Basically what it boils down to though is that I'm doing 2-volume/1-tone. So that means I'm going from pickups, to volume pots, to toggle switch, to tone pot and jack.

I've seen a lot of people recommend shielded wire from the toggle switch to the jack (for normal LP wiring), but I haven't seen anything about going from the pots to the toggle switch - should that be shielded as well? And in that case, would it work to use shielded 4-conductor cable (two in, one out, one ground) for the run from the pots to the toggle switch? Or would that cause issues with out-of-phase crosstalk messing with the signal?

 

[Cagey]

The short answer is: shield anything that will carry signal that isn't ground/common/neutral, and tie the shield(s) to ground/common/neutral. The longer the wire, the more important is is. In a guitar/bass, that's usually anything over 1" long. Shorter runs aren't practical to shield.

The long answer is...

Any time you cause current flow through a conductor, you create a magnetic field. Conversely, any time you have a magnetic field near a conductor, you induce (generate) a current flow.

Sometimes, you don't want that to happen. You may not want to interfere with another circuit, or have another circuit interfere with the one you're concerned with. In those cases, the interference is considered "noise" or unwanted signal, which at lower frequencies you can hear and it sounds like its name.

You have to think of EMI (ElectroMagnetic Interference) and RFI (Radio Frequency Interference) as a form of radiation, since that's what it is. Actually, they're both the same thing, but at different frequencies. That's another discussion.

You can't prevent the radiation - it's a physics thing. But, you can re-direct it. When you shield, what you're doing is picking up the radiation on purpose, and sending it to ground where it can't do any harm.

So, if you have a conductor that's going to radiate (remember - anything with an electrical current flow), you wrap it in another conductor (the shield), and tie it to ground. The shield picks up that radiation, and drains it away to ground so nothing else is affected. That's not usually an issue in guitars. The current flows involved are very small.

However, the inverse is a serious issue in guitars/basses. The desired signal (from your pickups) is so small that your amplifier(s) have to be super-sensitive and have a great deal of gain to get the signal large enough to be useful. As a result, the incredibly weak interference all around you from building wiring and other devices gets amplified as well. But, the shield trick still works. Wrap your signal conductors with another conductor, and tie it to ground. And surrounding radiation is picked up by the shield first and gets drained away, leaving you nothing but signal. No noise, things are quiet, life is good. And fair.

 

[NQbass7]

Alright, so shielding is yes. What's the verdict on 4-conductor?

 

[Cagey]

Alright, so shielding is yes. What's the verdict on 4-conductor?

That's fine. Desirable, even, for neatness' sake. Kills several birds with one stone.

The signal levels inside a guitar/bass are so small, there's effectively no such thing as self-interference or crosstalk, even if the wires are bundled within the same shield.

 

[NQbass7]

Awesome, I like neatness and it means less effort too.