DIY Shielded Wire

[iamdavidmorris]

I just got an order of shielded two conductor wire in and was pretty disappointed with it.  It was HUGE.  It was also cheap, and I didn't order much, so no big loss.  I'm out about eight bucks.  I'm sure somebody's tried this before, but I got to thinking it might be less trouble to just make my own shielded wire, especially since we generally use only a few inches at a time.  That way it can have as many or as few conductors as I want, be the size I want, and I can have it in as small a quantity as I want.  The thing I'm most uncertain about is what to use for shielding foil (since I'm obviously not going to be braiding wire).  Think this would work, assuming I remove the insulation from one conductor for a drain wire?

 

[line6man]

I don't see the point of this, if you're trying to wire a guitar. It's not going to do you any good to create a Faraday cage for a few inches of wire, when shielding an entire guitar has questionable effect to begin with, depending on how well it's done.

For the record, however, it would seem that creating a Faraday cage by means of copper tape wrapped around several insulated single-conductors as opposed to using shielded multi-conductor wire, would offer an advantage. The increased plate separation of having an air dielectric of a non-uniform thickness and contact between plates would make for a lower parasitic capacitance.  Of course, you're only dealing with a short length of wire to begin with, however, so the capacitance would be very low either way.  I would be concerned with how well the shielding works, though. Nothing beats a regular shielded lead, foil or braid.

 

[Jusatele]

Just remember to ground the shield so you do not create more noise than you had before buy making it a conductor of eddy currents, but wanna know something, the need to shield the small length of wire in a guitar is very questionable.

 

[line6man]

wanna know something, the need to shield the small length of wire in a guitar is very questionable.

Bingo.

 

[Dan025]

i dont know why everyone assumes copper is a better sheilding material. the comercial stuff that is foil shielded is usually aluminum not copper. fender also uses aluminum under its pickguards. according to bill lawrence aluminum has a greater ability to reject noise from a certain type of dimmer switch often used for stage lighting. fender does not use aluminum because it is cheaper nor do the conductor manufacturers. there is a legitamate advantage to aluminum over copper shielding. i wish i knew more about this topic. i dont like to go off here-say but i tend to trust what bill lawrence writes on his website, bill even says it is not nessesary to ground aluminum so it is not working off the faraday cage principle. aluminum has some pretty unique electromagnetic properties and will have a very high level of eddy curents when exposed to an electromagnetic field absorbing much energy and radiating it as heat. this may be why it can shield very well without much density but i am not a radio engineer. the eddy currents can be observed by taking a sheet of aluminum and a magnet and alowing the magnet to slide down the aluminum at an angle. the magnet will slide much slower than expected do to the eddy currents the stronger the magnet and thicker the aluminum the more you will see effects from the eddies. if the magnet is large enough and you move it over the aluminum fast enough it will make the aluminum hot, this is how speed is controlled on modern roller coaster tracks.

now about should you do it? well if the guitar is top routed it would be better to just shield the route. if is in rear routed and the switch is far from the output jack such as in a les paul then it might be a good idea for that run. but if you are talking about going from componants that are close to each other in the same cavity then just shield the cavity. the ratio of shielded length to exposed length on short runs makes it seem to me that shieldin short runs is a futile attempt. 

 

[line6man]

i dont know why everyone assumes copper is a better sheilding material. the comercial stuff that is foil shielded is usually aluminum not copper. fender also uses aluminum under its pickguards. according to bill lawrence aluminum has a greater ability to reject noise from a certain type of dimmer switch often used for stage lighting. fender does not use aluminum because it is cheaper nor do the conductor manufacturers. there is a legitamate advantage to aluminum over copper shielding. i wish i knew more about this topic. i dont like to go off here-say but i tend to trust what bill lawrence writes on his website, bill even says it is not nessesary to ground aluminum so it is not working off the faraday cage principle. aluminum has some pretty unique electromagnetic properties and will have a very high level of eddy curents when exposed to an electromagnetic field absorbing much energy and radiating it as heat. this may be why it can shield very well without much density but i am not a radio engineer. the eddy currents can be observed by taking a sheet of aluminum and a magnet and alowing the magnet to slide down the aluminum at an angle. the magnet will slide much slower than expected do to the eddy currents the stronger the magnet and thicker the aluminum the more you will see effects from the eddies. if the magnet is large enough and you move it over the aluminum fast enough it will make the aluminum hot, this is how speed is controlled on modern roller coaster tracks.

now about should you do it? well if the guitar is top routed it would be better to just shield the route. if is in rear routed and the switch is far from the output jack such as in a les paul then it might be a good idea for that run. but if you are talking about going from componants that are close to each other in the same cavity then just shield the cavity. the ratio of shielded length to exposed length on short runs makes it seem to me that shieldin short runs is a futile attempt. 

People like copper because you can solder to it easily. Plain and simple.

 

[Dan025]

why is it i never see the obvious?  :doh:

yeah i guess for a Faraday cage copper is better due to solderability. but aluminum may not even need to be grounded according to bill lawrence, so then begs the question, is a faraday cage better or is it better to just box everything in a material that turns electromagnetism into heat?(im assuing that has something to do with it anyway) that's not something i can answer.

 

[line6man]

why is it i never see the obvious?  :doh:

yeah i guess for a Faraday cage copper is better due to solderability. but aluminum may not even need to be grounded according to bill lawrence, so then begs the question, is a faraday cage better or is it better to just box everything in a material that turns electromagnetism into heat?(im assuing that has something to do with it anyway) that's not something i can answer.

I don't know why you're talking about thermal energy dissipation.
The idea behind shielding is to create a Faraday cage. Read about it here: http://en.wikipedia.org/wiki/Faraday_cage

FWIW, shielding MUST be grounded in order to work properly. It doesn't matter if it's aluminum or copper or something else. The principle is still the same.

 

[iamdavidmorris]

*waits for Cagey to jump in on shielding cavities*

It seems to me that either aluminum or copper would work.  I just know I've seen that snail stuff at Home Depot.  But I tend to agree with Justatele that if you're shielding wire, the shield should probably be grounded.  And I only think that because it's conventionally done.  I don't know all the science (though I do understand the purpose of a Faraday Cage).

 

[Dan025]

http://billlawrence.com/Pages/Pickupology/External%20Interference.htm

i am trying to find a link where bill goes into more details on using aluminum for noise cancelations, it used to be in a realy obscure location on his site and seems to have been moved or removed. some of what i said was speculation of why it works, but now that i thinkabout it it wont work on 60 cycle hum unless it is used as a faraday cage. but it may reduce higher frequency hiss and noise from old industrial dimmer switches that create a weird sawtooth like wave. they are called thyristor dimmers. according to bill aluminum shielding is the only thing that will reduce dimmer noise and it might only take about .003" of aluminum to do it even if it is not grounded.

http://en.wikipedia.org/wiki/Thyristor

 

[line6man]

old industrial dimmer switches that create a weird sawtooth like wave.

It's not a sawtooth wave! A sawtooth wave does NOT start on a peak like a square wave.
Bidirectional triode thyristors, or TRIACs, as they are usually termed, are a pair of silicon controlled rectifiers in inverse parallel, so that they will work with alternating current.
A silicon controlled rectifier is a diode with a gate terminal that will conduct after the gate is triggered. If you run a sinusoid through a TRIAC, depending on the firing angle, it won't start at 0V and build up to the 90 degree peak, and then back down to the 180 degree 0V point again, it will stay at 0V for few degrees, then jump straight to some amplitude, and continues on for the rest of the half cycle.

Here is a graphic.

 

[Dan025]

great you are familiar with dimmer switches. notice i said sawtooth "like" wave. as it is not a sine wave, it is not a square wave but in a way it loosely resembles a sawtooth wave. though you are certainly right a sawtooth does not sit at 0 for a few degrees then snap to a voltage, it would snap yo a voltage as soon as it hit zero then fall in a linear pattern and not follow a sine wave at all. it was only a rough description. the important part is that these dimmers put off emi that is apparently difficult to shield against and aluminum apparently helps for this particular type of interference. but thank you for clarifying those things.

 

[line6man]

notice i said sawtooth "like" wave. as it is not a sine wave, it is not a square wave but in a way it loosely resembles a sawtooth wave.

This is all completely irrelevant to the topic, but still, it does not resemble a sawtooth wave at all! I don't see where you're getting that idea. The two waveforms could not be any more dissimilar.  :blob7:

 

[Cagey]

Forget about waveshapes - it's all about induction. If you have a current flow through a conductor that's adjacent to another conductor, a current flow will be induced into the quiescent conductor. I don't care if the waveshape spells your name; it makes no difference. It's all about flux density, conductivity and proximity.

As for Bill Lawrence's hard-on for aluminum, that's just a pet theory of his with no basis in fact. I don't know why he's fixated on the stuff, but there's no harm in it. At the signal levels and frequencies where guitars operate, and the interference guitar amplifiers are sensitive to, the relative conductivity of the shielding is of little or no consequence past a certain point. It simply needs to be there and it'll be effective.

Faraday cages only work if there are no holes in them larger than the wavelength of the signal you're trying to block. So, right off the bat you're doomed to failure. You gotta cut holes for the pickups, right? Besides, the biggest and most sensitive part of a guitar's wiring IS the pickup, which is necessarily is outside the cage should you decide to build one. So, you're wasting your time. The cage has huge holes in it, and there are antennae sticking out that are connected to very high impedance amplifier inputs. This has failure written all over it if your object is to ignore external signals, and that's been proven 78 bajillion times. Why does anybody suppose Fender and Gibson don't do the insane shielding that some private builders do? Do they think the biggest, richest, highest-priced guitar manufacturers just want to piss off their clientele? Don't be silly. It's not a money thing. They just know better. Most engineers worth their salt do.

That's not to say shielding is unimportant or ineffective. But, it has to be done properly. It's impossible to do completely on a guitar, but it can be taken to a very effective degree by simply shielding the signal wiring itself, or using a common-mode rejection pickup system. Seth Lover of Gibson fame came up with what he called the "humbucker", which does this. Even got a patent on the idea, even though it was nothing new. It was simply a new application of an old discovery. Many pickups since then do the same thing. different packaging schemes produce different sonic results, but the basic concept is the same: reject the common signal through cancellation and keep the differential. Works like a champ.

 

[Jusatele]

I have a strat with an aluminum pickguard, now that shouldbe the best aluminum shield you could get ever. Nope, noisiest axe in the stable.

 

[elfro89]

I don't see the point of this, if you're trying to wire a guitar. It's not going to do you any good to create a Faraday cage for a few inches of wire, when shielding an entire guitar has questionable effect to begin with, depending on how well it's done.

For the record, however, it would seem that creating a Faraday cage by means of copper tape wrapped around several insulated single-conductors as opposed to using shielded multi-conductor wire, would offer an advantage. The increased plate separation of having an air dielectric of a non-uniform thickness and contact between plates would make for a lower parasitic capacitance.  Of course, you're only dealing with a short length of wire to begin with, however, so the capacitance would be very low either way.  I would be concerned with how well the shielding works, though. Nothing beats a regular shielded lead, foil or braid.

I know now, your a feckin rocket scientist!

 

[line6man]

I have a strat with an aluminum pickguard, now that shouldbe the best aluminum shield you could get ever. Nope, noisiest axe in the stable.

I think the shielding that is normally factory-applied to Strat pickguards is only applied so that the pots and switch will be grounded, even if you don't decide to ground the backs of each pot. That's why the cheaper pickguards only have shielding around the controls.Shielding a Strat pickguard beyond the control area is useless, because so much of the area of the pickguard has nothing to do with the wiring.
Now on the other hand, I've heard a few people complain of static discharges in ungrounded pickguards, and shielding the pickguard (*Or more properly, GROUNDING the pickguard.) took care of it.

As usual, my opinion on the matter is this:
The effects of shielding are questionable, but there is absolutely no reason NOT to shield anyways, just so long as you're not going overboard with it.
As Cagey pointed out, you cannot form a proper Faraday cage in a guitar, because you cannot enclose the pickups in a grounded shield, so for that reason, you cannot expect much, but as long as you're not going to extreme lengths to try, what reason is there not to shield your guitar?

 

[line6man]

I don't see the point of this, if you're trying to wire a guitar. It's not going to do you any good to create a Faraday cage for a few inches of wire, when shielding an entire guitar has questionable effect to begin with, depending on how well it's done.

For the record, however, it would seem that creating a Faraday cage by means of copper tape wrapped around several insulated single-conductors as opposed to using shielded multi-conductor wire, would offer an advantage. The increased plate separation of having an air dielectric of a non-uniform thickness and contact between plates would make for a lower parasitic capacitance.  Of course, you're only dealing with a short length of wire to begin with, however, so the capacitance would be very low either way.  I would be concerned with how well the shielding works, though. Nothing beats a regular shielded lead, foil or braid.

I know now, your a feckin rocket scientist!

I thought you said you loved physics? It's all fascinating stuff when you study it. :icon_biggrin:

 

[elfro89]

I don't see the point of this, if you're trying to wire a guitar. It's not going to do you any good to create a Faraday cage for a few inches of wire, when shielding an entire guitar has questionable effect to begin with, depending on how well it's done.

For the record, however, it would seem that creating a Faraday cage by means of copper tape wrapped around several insulated single-conductors as opposed to using shielded multi-conductor wire, would offer an advantage. The increased plate separation of having an air dielectric of a non-uniform thickness and contact between plates would make for a lower parasitic capacitance.  Of course, you're only dealing with a short length of wire to begin with, however, so the capacitance would be very low either way.  I would be concerned with how well the shielding works, though. Nothing beats a regular shielded lead, foil or braid.

I know now, your a feckin rocket scientist!

I thought you said you loved physics? It's all fascinating stuff when you study it. :icon_biggrin:

I do, but what you were talking about was well above my head. I don't believe someone would know as much about it if it wasn't their profession or serious hobby. You don't strike me as the hobbyist in regards to this... nah nah, your definitely involved professionally in something around this area...

 

[Jusatele]

Just wrap the entire thing in a double coat of bubble wrap