Shielded cavities vs shielded wire

[Chistopher]

So I was thinking today, why bother shielding the whole cavity if the only thing picking up interference is the wires. You can shield the pickups, but that affects tone; the pots are themselves shields; and everything else is grounded to the bridge. That leaves the only thing unprotected when not using shielding to be the wire. Wouldn't it be easier to just use shielded wires if they block the same amount of interference?

 

[AlexR]

Re: Shielded cavities vs shielded wire

If you've ever done soldering in tight spaces you'll find cavity shielding way more easy to complete.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

I'm mostly thinking about strats, where you can just take the whole pickguard out. I understand why it would be easier to shield a p90 les paul for example, but if you are wiring up a guitar anyway, why not just do it with shielded wires?

 

[darthphineas]

Re: Shielded cavities vs shielded wire

Wouldn't it be easier to just use shielded wires if they block the same amount of interference?

Try it both ways and see what works best for your setup.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

This is just a general question, not for a specific guitar. I just find it interesting that many guitar makers go through the trouble of making a guitar with a shield, which costs more and takes more time, if they could just use shielded wires in the first place. I for the most part use shielded wires just out of ease of use.

 

[Eric Dahlberg]

Re: Shielded cavities vs shielded wire

Many people believe cloth covered wire sounds different. Given that passive pickups are super high impedance, they're probably correct to some extent.

 

[thanaton]

Re: Shielded cavities vs shielded wire

So I was thinking today, why bother shielding the whole cavity if the only thing picking up interference is the wires. You can shield the pickups, but that affects tone; the pots are themselves shields; and everything else is grounded to the bridge. That leaves the only thing unprotected when not using shielding to be the wire. Wouldn't it be easier to just use shielded wires if they block the same amount of interference?

Shielding wires dramatically increases parasitic capacitance, compared to shielding the control cavity. It's not a trivial thing, either. Shielded hookup wire tends to be worse with respect to capacitance than guitar cable, because shielded wire, the type used in Les Paul's for example, has an even thinner insulation layer between the lead wire and shield layer than a typical guitar cable. While a guitar cable adds maybe 30 to 40pf capacitance per foot, that shielded hookup wire adds close to 70pF per foot.

 

[Darg1911]

Re: Shielded cavities vs shielded wire

They do it because shielded wires don't take the place of shielding the cavities. What's interesting (to me) is that every Asian import I have had the cavities shielded with carbon paint at the factory. Pretty sure they all had shielded wiring as well (if they didn't, they do now, at least those with the switch located in a separate cavity. They are all quiet too. The others ... if they are noisy, I shield them. Just did a LP a couple weeks ago. It made a huge difference.

Edit. Apparently I got lost somewhere so ... nevermind.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

Thanaton, given that the wires in a guitar are so short, does it really make that much of a difference?

 

[thanaton]

Re: Shielded cavities vs shielded wire

Thanaton, given that the wires in a guitar are so short, does it really make that much of a difference?

It's a personal preference, really. Some people really hate losing any high end to cable capacitance and go to extraordinary lengths to minimize it, like this guy http://zerocapcable.com/?page_id=231 , but then you have guitarists like Hendrix who used those coiled guitar chords which add a ton of capacitance, and they seem to appreciate the loss of high end.

Personally, I like clear cleans, so I try to reduce capacitance as much as I can. If I can cut out 70pF, I will.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

I guess shielding would also work better with, say, a superswitch. There could potentially be issues with braided cables touching each other and causing electrical problems.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

And while we are on the subject of shielding, what are your opinions on the whole copper versus aluminum debate?

 

[darthphineas]

Re: Shielded cavities vs shielded wire

And while we are on the subject of shielding, what are your opinions on the whole copper versus aluminum debate?

To a degree, using both can be more beneficial, based on how they each handle their own things. But... like the original question, it can be splitting hairs.

I've tried copper and aluminum and conductive paint and addressing just a strip where the pots mount and all the cavities (including them trem cavity) and the results can be the same or the results can vary.

Some of it can also be addressed with where the interference is coming from.

 

[beaubrummels]

Re: Shielded cavities vs shielded wire

So I was thinking today, why bother shielding the whole cavity if the only thing picking up interference is the wires. You can shield the pickups, but that affects tone; the pots are themselves shields; and everything else is grounded to the bridge. That leaves the only thing unprotected when not using shielding to be the wire. Wouldn't it be easier to just use shielded wires if they block the same amount of interference?

My experience is that it works, and is easier to implement than chasing every other minor touch point in the wiring harness where interference could be getting in.

 

[thanaton]

Re: Shielded cavities vs shielded wire

And while we are on the subject of shielding, what are your opinions on the whole copper versus aluminum debate?

The difference would purely in terms of how easy or difficult it is to install in the guitar. Aluminium is technically more conductive than copper, but both metals are conductive enough that they would be equal in terms of how well they block noise. Probably the biggest difference is that it's really difficult to solder aluminium, so you have to really on metal to metal contact, which isn't a big deal so long as the joint is secure and air tight.

 

[darthphineas]

Re: Shielded cavities vs shielded wire

I wonder if there is anything on the guitarnuts board about shielding.

 

[Darg1911]

Re: Shielded cavities vs shielded wire

I realized after first posting yesterday that the discussion seemed to be about adding a shield to the wire, not shielded wire as I initially thought. I've never tried adding a layer of shielding to an already shielded wire. It's kind of counterintuitive to me, but maybe it works just by doubling up on the shield. I don't know. I just paint the cavities if I find it necessary (or use a tape/foil shield).

As Thanton mentions, that vintage braid wire is really high capacitance. If you want to cut down on the capacitance inherent in the vintage style braided wire, there is always something like RG-174 mini coax. The decent stuff is about half the capacitance of the vintage braid.

 

[uOpt]

Re: Shielded cavities vs shielded wire

You are partially confused. The pickup wire around the pickup magnets picks up both electromagnetic and electrostatic interference. If it is not a humbucker you can lower the latter (but not the former) by shielding the cavity. That is a lot more effective than using your belly as a partial shield which is what happens when you ground yourself via the bridge.

Now, since the non-humbucker pickup still picks up electromagnetic interference just cutting down on electrostatic interference via shielding isn't all that effective, and there is a possibility that the pickup cavity shielding influences sound (mainly due to eddy currents, but I would rule out mechanical effects either).

IMHO it is perfectly reasonable to shield cables and cavity but leave the pickup cavities bare. It would be better to do blind A/B testing, of course. Whether the shielding in the pickup cavities indeed influences sound is questionable, and it depends on other factors such as pickup height and cavity depth.

 

[darthphineas]

Re: Shielded cavities vs shielded wire

Vintage braid capacitance depends on the weave.

 

[Chistopher]

Re: Shielded cavities vs shielded wire

So that RG-174 stuff cuts down on interference? I might consider it in future builds. It's pretty cheap too, and that's always a plus.