Crosstalk in 4-conductor shielded wire?

[Verne Bunsen]

Hi all,

I'm working on wiring up a guitar in the Les Paul fashion (2 Vol, 2 Tone, 3-way toggle), and I'm using 4-conductor shielded cable as follows:

Red: Neck volume pot output to switch
Green: Bridge volume pot output to switch
White: Switch output to jack tip
Black: Switch ground lug to output jack sleeve
Bare: Switch ground lug to common ground (pot case)

In function testing the harness, I find that I can hear tapping on the poles of the pickup that is not selected in addition to the pickup that is selected. So if the neck pickup is selected, tapping the neck pickup produces a loud pop as expected and tapping the bridge pickup produces a softer pop. Likewise if the bridge pickup is selected, tapping the bridge pickup produces a loud pop and tapping the neck pickup produces a softer pop. A couple of interesting points yielded by troubleshooting:

If both pickups are disconnected (desoldered and physically separated from the connection) at the switch, tapping either still produces a pop.

If the wires from the volume pot output to the switch are disconnected at both ends, touching either wire induces noise at the guitar output.

I can only gather that the 4-conductor bundle is cross talking? I have a Les Paul that is wired in the same way; I checked it an lo and behold, I can hear soft pops if I tap the unselected pickup. Checking my other Les Paul, which is wired in "vintage" fashion with single conductor braided wire, the unselected pickup is silent. The wirings are identical point-to-point, the only difference is the wire used. Has anyone else encountered this?

Thanks for any insight.

-VB-

 

[Cagey]

It's not electrical crosstalk, it's mechanical. Tapping on one pickup makes the whole guitar vibrate, so the other pickup feels it. It's one of the reasons I started using a tuning fork to test pickup operation rather than just tapping on them. Plus, you get a long, continuous signal out of the pickup with a fork, so you can better hear how the volume and tone knobs behave.

Tuning forks are pretty inexpensive. One like this standard 440hz "A" from Amazon is only $5.99...

Or, next time you're at the music store picking up some strings or picks, get one there.

 

[Verne Bunsen]

Thanks for the input Cagey! In this case, the harness was being tested out of the guitar, so both pickups were actually sitting on the tacky blue shag rug that my gear lives on, no mechanical coupling. Also, I was able to induce noise sans-pickup by touching the volume-pot-to-switch wire even with it disconnected at both ends!

 

[rgand]

Tuning forks are pretty inexpensive. One like this standard 440hz "A" from Amazon is only $5.99...

I got one just like that 30+ years ago. Kept it all these years and it's only worth $6? Maybe $3 adjusted for depreciation?  :icon_biggrin:

At least I have a new use for it. Thanks for the tip.

 

[Cagey]

Thanks for the input Cagey! In this case, the harness was being tested out of the guitar, so both pickups were actually sitting on the tacky blue shag rug that my gear lives on, no mechanical coupling. Also, I was able to induce noise sans-pickup by touching the volume-pot-to-switch wire even with it disconnected at both ends!

Hmm... I don't know what to tell you, other than perhaps the harness is haunted. I mean, if grabbing a wire that's not connected to anything on either end makes noise, what other explanation is there?

 

[Cagey]

I got one just like that 30+ years ago. Kept it all these years and it's only worth $6? Maybe $3 adjusted for depreciation?  :icon_biggrin:
At least I have a new use for it. Thanks for the tip.

Mine's even older than that. Used to use it to tune my acoustic when I was in grade school. Get it ringing and touch the ball end of it to the top of the guitar, and it would amplify it nicely.

For testing pickups, you don't touch anything, you just get it ringing and hold it over the pickup as if it were a vibrating string. Works great.

 

[rgand]

For testing pickups, you don't touch anything, you just get it ringing and hold it over the pickup as if it were a vibrating string. Works great.

Thanks, I'll try that when I assemble my current build. I used mine to tune my mandolin and later my guitar way back when.

 

[Verne Bunsen]

Hmm... I don't know what to tell you, other than perhaps the harness is haunted. I mean, if grabbing a wire that's not connected to anything on either end makes noise, what other explanation is there?

Thats it exactly. The 4-conductor cable is carrying both pickup signals to the switch and the switch output to the jack. So if both signals are in the output regardless of switch position (albeit with the "unselected" pickup much weaker), and if the interference of touching an input wire is audible in the output even if the input wire is disconnected at both ends, then in my mind (which, granted, is a pretty unusual place), some kind of communication between the input and output wires within the cable is the only thing I can make out of it.

The harness is going into my ES-137 and the last thing I want is electrical gremlins once I stuff all the parts back in, so I think I will save this harness for future science and start over with a metal braid single conductor wire harness...

 

[Cagey]

Well, since the disconnected wire you're touching is inside the shield, then instead of a receiver it's acting as a transmitter that the other wires have no protection against, since they're inside the shield as well.

I've never heard of pickup wire crosstalk, but then they're not usually bundled in such close proximity. When I wire that sort of thing, I always use the braided single conductor (+shield).

No way you're getting crosstalk with that. Plus, it's a much more robust wire than that 4 conductor stuff that's finer than frog's hair.

 

[Verne Bunsen]

No way you're getting crosstalk with that. Plus, it's a much more robust wire than that 4 conductor stuff that's finer than frog's hair.

Roger that. The whole time I was wiring the harness I was having growing concern over those tiny joints being able to survive the stresses of re-installation. The harness itself was quite stout, but all of the connection points were disconcertingly delicate.

The next one will be better!

 

[Cagey]

That's too bad. That's a really well-done harness. Hate dismantling stuff like that.

 

[Verne Bunsen]

Thanks! I did my darndest there, my son said I should hang it on the wall  :toothy12:

 

[BigSteve22]

I got one just like that 30+ years ago. Kept it all these years and it's only worth $6? Maybe $3 adjusted for depreciation?  :icon_biggrin:
At least I have a new use for it. Thanks for the tip.

Mine's even older than that. Used to use it to tune my acoustic when I was in grade school. Get it ringing and touch the ball end of it to the top of the guitar, and it would amplify it nicely.

For testing pickups, you don't touch anything, you just get it ringing and hold it over the pickup as if it were a vibrating string. Works great.

Wow, I gotta retire, look at the great threads I miss while I'm supposed to be working!

Anyway, I've got the same tuning fork, gotta be 45 years old now. Bought it to tune my acoustics, still use it as described to test pup wiring.

Thanks! I did my darndest there, my son said I should hang it on the wall  :toothy12:

Gotta agree with Kevin here, that's way to nice to dismantle. Personally, I'd put it on eBay as a genuine "Ghost in the Wires" harness, probably pull in enough to finance your next build!  :laughing3: :laughing11: :laughing7:

 

[Verne Bunsen]

Gotta agree with Kevin here, that's way to nice to dismantle. Personally, I'd put it on eBay as a genuine "Ghost in the Wires" harness, probably pull in enough to finance your next build!  :laughing3: :laughing11: :laughing7:

"Add some spontaneity to your playing by never being sure which pickup you're using! The all new "Heisenberg Harness" will keep your fans guessing!"  :toothy12:

 

[Verne Bunsen]

Still not sure what was going on in the other harness, but I'm going to file it under "everything happens for a reason". I'm much more satisfied with the durability of this new harness. Also I like that it checks out functionally  :icon_biggrin:

 

[Cagey]

Very nice! Even if it don't work, install it anyway  :laughing7:

 

[Verne Bunsen]

Thanks! Now for the really fun part: getting the guts back into the patient...

 

[Cagey]

A lotta guys use strings to fish the parts through, but I've found it to be a bit easier to use solid-core wire. Nothing huge, just some 24ga or so. Gives you a bit of leverage to move the end of the line from a ways back, which you can't do with a string.

 

[stratamania]

Thanks! Now for the really fun part: getting the guts back into the patient...

Look closely around 2:15

[youtube]https://www.youtube.com/watch?v=VNh2E0ZTf_g[/youtube]

 

[Verne Bunsen]

A lotta guys use strings to fish the parts through, but I've found it to be a bit easier to use solid-core wire. Nothing huge, just some 24ga or so. Gives you a bit of leverage to move the end of the line from a ways back, which you can't do with a string.

I tied strings to the pots and hooked a wire around the jack when I fished everything out; the wire for the jack should work well for bringing it back but I’m questioning the string. It’s been a couple of days since I started this and they are kind of a tangled mess at this point...

Look closely around 2:15

Ah! I tried that with vinyl tubing and found that, while the nuts and washers would clear its OD in a fit test, once I got the pot shaft in there it expanded to where I could no longer get the hardware over it. Surgical tubing.....