Shielded Wire Advice?

Ginsly

Ginsly

Well-known member
I've looked at some past threads regarding shielded wire for Input and Output connections, but I'd love to know some of your current go-to sources for it. I've seen some mention pain 'ol RG-174 spools - seems like it might not have a tinned core and could be tough to work with, though.

I also have conductive copper tape from shielding guitars - couldn't I just carefully wrap that around a normal wire, connect a piece of wire from the copper to the jack sleeve, and insulate the whole thing with heat shrink? That sounds like a bigger pain, but my budget is pretty depleted for now!

I'm not sure this will make any difference, but I have a LOT of interference in my area and I'll do anything to minimize noise.
 
Ginsly said:
I've looked at some past threads regarding shielded wire for Input and Output connections, but I'd love to know some of your current go-to sources for it. I've seen some mention pain 'ol RG-174 spools - seems like it might not have a tinned core and could be tough to work with, though.

I also have conductive copper tape from shielding guitars - couldn't I just carefully wrap that around a normal wire, connect a piece of wire from the copper to the jack sleeve, and insulate the whole thing with heat shrink? That sounds like a bigger pain, but my budget is pretty depleted for now!

I'm not sure this will make any difference, but I have a LOT of interference in my area and I'll do anything to minimize noise.
Click to expand...
1. Here's what I use (was recommended to me by another forum member) - $7.99 at Amazon.

2. I've actually used the "wrapping copper tape around a wire and grounding it" trick once in a pinch. It worked but, yes, kind of a pain.

Mike
 
And just to clarify - it's good to use shielded wire on the Input and Output wires going from the actual JACK tips to the 3PDT pcb, NOT the wires going from "Board Input" and "Board Output" on the pcb to the corresponding pads on the 3PDT pcb, correct?

I ask because I was having some noise issues with Board Input on a vero build, and was going to try shielded wire there. Sounds like it might not do a whole lot for this situation though.
 
Ginsly said:
And just to clarify - it's good to use shielded wire on the Input and Output wires going from the actual JACK tips to the 3PDT pcb, NOT the wires going from "Board Input" and "Board Output" on the pcb to the corresponding pads on the 3PDT pcb, correct?

I ask because I was having some noise issues with Board Input on a vero build, and was going to try shielded wire there. Sounds like it might not do a whole lot for this situation though.
Click to expand...
I only use it on the input and output jacks. I would think that, because they run of wire from the board to the 3PDT is so short, it wouldn’t make that much difference, but it certainly wouldn’t hurt anything to also put them there either.

I never bothered with it because, given that that run of wire is generally only about an inch or two long, once you’ve stripped it on one end so you can ground the shielding at one end and you’ve stripped part of the other end and removed the shielding so you can connect the core, there isn’t a whole lot of the wire that’s actually left covered/shielded.
 
mkstewartesq said:
I only use it on the input and output jacks. I would think that, because they run of wire from the board to the 3PDT is so short, it wouldn’t make that much difference, but it certainly wouldn’t hurt anything to also put them there either.
Click to expand...
Gotcha, makes total sense. There's a weird situation where I might install the pcb upside-down (only way it'll fit in a certain enclosure 🤦‍♂️), so those connections would obviously be longer. I'll have to try that if I wind up flipping it around.
 
Shielding can be very helpful in reducing noise in your circuit, but it may not always be a good idea. It's best to use shielded cabling only when it's needed - like when you're troubleshooting a particularly noisy pedal, or you're getting cross talk, or picking up random radio stations, etc.

If you do decide to use shielded cable, there are a couple of things you should keep in mind. First, it changes the capacitance of your signal (inside a guitar pedal the lengths of cable you are using isn't going to be noticeable, but just like using a long guitar cable, it can affect the quality of your sound, and if you're stacking a bunch of pedals together, it can become noticeable. Also, it is good to be mindful about how you terminate the shielding. In order to be effective, the shield has to be grounded, but if there are different reference ground voltages inside the pedal, you can create ground loops that can add noise to your circuit. To prevent this, a lot of people will only ground one end of the shield, but by doing that you may actually be adding an antenna to your circuit.

Don't get me wrong, I think shielding is great, and it is a very useful tool, and sometimes it's absolutely necessary, but it also becomes something else you have to troubleshoot when things aren't working right. In my opinion it's better to use shielding as tool to solve noise problems and not as a prophylactic to prevent them. -- Just my two cents.
 
@chris.knudson It’s helpful to hear this perspective again. Weeks ago I had kind of written it off as unnecessary since everything is already in a Faraday Cage, pretty much. Just reconsidering it now.

I’m mostly building fuzz pedals that are susceptible to noise and create noise too, depending on the components chosen (transistors, etc). They can use all the protection possible, but I realize the actual noise floor may not change without switching out components (or adding a bias control to gate when possible).

Grounding on only one end of the wire did seem odd, but sounds like that’s the standard practice.
 
On the rare occasion I use shielded cable internally, I use some solid core stuff I think I got from small bear a year ago or so. It's some brand of no-solder patch cable wire(think George Ls). Small enough to be flexible but rigid enough to stay where I put it. I always ground shield to the jack and only to the jack, ensuring a chassis ground.
I make it common practice in any pedal with a clock of any sort, being digital or a crystal.
Always follow star grounding practices when you can. Grounding both ends can cause ground loops. You need it grounded so the noise goes to ground. That's the whole point. Not grounding one end invites it to pick up noise(as intended) and allow it to leech into the audio line.
As Chris mentioned, it could cause issues if a virtual ground is used but that's rare in pedals and also that ground should be isolated from chasis ground. If it's not, there are bigger issues with the circuit and the shielding won't be the problem.

I think this is what I use.
Tightrope Low cap cable @70 cents/ft
 
I’ve found shielded wire to be one of those “1%” considerations.

I do it anyway though because after working on the whole package to eliminate noise, I definitely hear a difference with shielded wire on the I/O.
 
Revisiting this thread. Haven't used shielded wire yet, but I'm on a mission to kill avoidable noise.

Seems like there's still some debate about this:

- Some say "it might not help, but couldn't hurt". Some say "it could act as an antenna and pick up MORE noise".

- Most say to ground only one end - for example, when used as the Input wire you would ground to the jack's sleeve but not at the 3PDT. Some say this may attract MORE noise. I've only ever seen it grounded on one end, though.

- Figured I'd just grab some of this like @mkstewartesq mentioned, but the reviews say it's not "true RG174" in that the braid isn't as tight and it's not tinned. I have to assume that doesn't matter in pedal applications.

The input so far has been helpful, but I'm still not sure what the scoop really is. Would love to hear your experiences with it.
 
I use MIL-W-16878/6 and ground at the jacks only. Then jumper the jacks to the PCB or DC jack as normal.
You ground it however it creates a star ground scheme. If you pick up clock noise on the shield, you want it to travel AWAY from your audio and straight to the ground input, IE away from the footswitch.
A shield shouldn't be used as a ground. Those are 2 different things. We don't shield guitar cable to have a ground. We ground shields to have a shield. The equipment input manages the ground.
 
jwin615 said:
I use MIL-W-16878/6 and ground at the jacks only. Then jumper the jacks to the PCB or DC jack as normal.
You ground it however it creates a star ground scheme. If you pick up clock noise on the shield, you want it to travel AWAY from your audio and straight to the ground input, IE away from the footswitch.
A shield shouldn't be used as a ground. Those are 2 different things. We don't shield guitar cable to have a ground. We ground shields to have a shield. The equipment input manages the ground.
Click to expand...
Saw this scenario in another thread: When using metal jacks on an aluminum enclosures, it looks like using jack-ground-only shielded wire on BOTH Input and Output would create a ground loop... Would it be better to only use shielded wire at the Input to avoid that? Otherwise it looks like a plastic Out jack would be needed...
 
No ground loop if you only connect one end of the shield to ground.
If you shield the jack end only, you only have one point of contact and are only extending the shield/ground over the wire.
If you ground both ends, which you shouldn't do, then you create loops, albeit small ones.
 
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