Cavity shielding

[moobox]

Hello all
You know, I'm just about to start the finish on a Stratocaster body and something struck me. I've got this copper tape and also some aluminium stuff as well. At what stage do I do the shielding on the cavities? Before any coats go on the guitar? Also, do I shield every cavity front and back?
Cheers - Ed

 

[line6man]

Shielding goes on just before wiring the guitar.

You need to do your best to create a complete enclosure, but this is nearly impossible to do, considering that the pickup cavities are open on the top. This is why shielding is often useless, as an incomplete Faraday Cage does nothing.

 

[Cagey]

Line6man is right. Shielding control or pickup cavities is an exercise in futility unless you just happen to like the look of copper- or aluminum foil-lined or conductive-painted cavities that nobody will ever see. Any opening at all defeats the entire thing, and the pickup openings are huge. They're like screen doors on a submarine. Plus, it's generally the pickups that pick up all the noise anyway unless you're using CMNR ("humbucking" or "noiseless") pickups, then the wiring becomes the major offender. The best you can do is to use shielded cable wherever possible internally.

You'll notice none of the major manufacturers do it, even though it wouldn't cost much and they'd be heavily motivated to do so. There's a reason for that: it's pointless.

 

[line6man]

Line6man is right. Shielding control or pickup cavities is an exercise in futility unless you just happen to like the look of copper- or aluminum foil-lined or conductive-painted cavities that nobody will ever see. Any opening at all defeats the entire thing, and the pickup openings are huge. They're like screen doors on a submarine. Plus, it's generally the pickups that pick up all the noise anyway unless you're using CMNR ("humbucking" or "noiseless") pickups, then the wiring becomes the major offender. The best you can do is to use shielded cable wherever possible internally.

You'll notice none of the major manufacturers do it, even though it wouldn't cost much and they'd be heavily motivated to do so. There's a reason for that: it's pointless.

I still say you should shield regardless. It's not hard to do.

FWIW, shielding works on electrical noise. Humbucking pickups usually cancel 60Hz hum by common mode rejection. Two different noises. (Or if you want to argue one cannot exist without the other, or something again, they are noises in two different frequency ranges.)

 

[Cagey]

I still say you should shield regardless. It's not hard to do.

FWIW, shielding works on electrical noise. Humbucking pickups usually cancel 60Hz hum by common mode rejection. Two different noises. (Or if you want to argue one cannot exist without the other, or something again, they are noises in two different frequency ranges.)

You're right in that it's not hard to do. But, it is a waste of time, effort and money.

All electrical noise is the same. It's a modulating magnetic field. The only things that change are frequency and field strength. Humbucking pickups do cancel 60hz noise, but they also cancel 22hz noise, 1,926hz noise, 15.2khz noise, all the way up into the microwave range. In other words, any signal that's common between two identical sensors wired out of phase will cancel. Frequency isn't an issue. 60hz is simply what we most often hear because that's the strongest and most prevalent ambient electrical noise in North America. In Europe, they hear mostly 50hz noise. Humbuckers work there, too. They're natural-born killers <grin>

 

[Patrick from Davis]

If you would like to use shielded cord, it is just like the cord that goes into your guitar, but smaller to fit in the cavities, I would suggest this stuff.  It has two layers of teflon insulation.  In general the stuff with regular insulation material melts quite quickly when soldering, and the inner wire touches the shield.  Annoying.  The cost difference is minimal, and this is nicer stuff.
Patrick

 

[Cagey]

Damn. I wish I'd have known about that supplier before now. I just bought a 100' reel of shielded cable and paid substantially more than that for it.

 

[Jusatele]

personally I do not even bother, the thing will not be shielded as far as the pickup is not in the cavity, a major part of it is hanging out, so what is the use.

 

[Cagey]

personally I do not even bother, the thing will not be shielded as far as the pickup is not in the cavity, a major part of it is hanging out, so what is the use.

In the case of true single coils, that's absolutely true. You'll notice in most single coil equipped guitars that they don't even try. Not even the control wiring is shielded. They use that old WWII cloth-insulated crap. But, if you have noiseless pickups, you still need to shield the cabling that's running around or it'll pick things up. Just the 4 to 6 inch run from the volume pot to the output jack will pick up all kinds of noise if it's not shielded, even if you're using humbuckers. Even the old Gibsons did that. Pickups didn't make any noise, but the wiring certainly would.

I still get a kick out of the pickguard makers who'll add a layer of aluminum foil under the pots. What do they think they're accomplishing? Satisfying customers who don't know any better. Doesn't do anything for noise. It's like hiding under a table for protection from tear gas.

 

[stubhead]

On the other hand, if you use real copper stickum "shielding" AKA ground, and you happen to notice the pots stuck right through it, it may reduce the temptation to ground your pots by soldering wires to the back of them, which has to rank in the top five idiotic-copied-ideas when you're building one-off guitars by copying production shortcuts from factories.

 

[line6man]

I still get a kick out of the pickguard makers who'll add a layer of aluminum foil under the pots. What do they think they're accomplishing? Satisfying customers who don't know any better. Doesn't do anything for noise. It's like hiding under a table for protection from tear gas.

Helps with static problems. :dontknow:

 

[Cagey]

On the other hand, if you use real copper stickum "shielding" AKA ground, and you happen to notice the pots stuck right through it, it may reduce the temptation to ground your pots by soldering wires to the back of them, which has to rank in the top five idiotic-copied-ideas when you're building one-off guitars by copying production shortcuts from factories.

While I wholeheartedly agree that soldering grounds to pot bodies is poor practice, I'm not sure shielding cavities to get that connection is the appropriate alternative. That would fall under the purvey of the "happy accident once you've done something unnecessary" department <grin>

 

[Cagey]

I still get a kick out of the pickguard makers who'll add a layer of aluminum foil under the pots. What do they think they're accomplishing? Satisfying customers who don't know any better. Doesn't do anything for noise. It's like hiding under a table for protection from tear gas.

Helps with static problems. :dontknow:

Really? I've never had that problem, but I'm not sure I've ever had a pickguard that didn't have at least a little bit of foil on the back. I'll have to file that one away in the back of my head for future reference. I've always attributed it to cheap pickguards made out of the wrong kind of plastic.

Pickguards are one of those things that even though I've had the tools and know-how to make, I've always left for someone else to do. All you have to do is make one to put you off it forever. Even just drilling holes or routing pickguard openings in one will teach you a lesson about the kind of mess machining plastic makes. You'll be cleaning bits of that crap up for months. When you consider that competition has made professionally made parts no more expensive than $25 for most designs, it seems foolish to even look down that road, let alone follow it.

 

[Rickgrxbass]

...an incomplete Faraday Cage does nothing.

Well, now, I hear it makes a durn good antenna, which is something...  :-\

Anyway, thanks to Fringe, now whenever I think of Faraday cages, I think of the villain who embedded a Faraday cage into his skin 

 

[Jusatele]

PS Ricky

change name to Snarky

that snarky enough?

 

[line6man]

...an incomplete Faraday Cage does nothing.

Well, now, I hear it makes a durn good antenna, which is something...  :-\

Anyway, thanks to Fringe, now whenever I think of Faraday cages, I think of the villain who embedded a Faraday cage into his skin 

Not when it exists at ground potential.

 

[stubhead]

Pickguards are one of those things that even though I've had the tools and know-how to make, I've always left for someone else to do. All you have to do is make one to put you off it forever. Even just drilling holes or routing pickguard openings in one will teach you a lesson about the kind of mess machining plastic makes.

Which is pretty much why, in all his infinite wisdom, God (or was it Chuck Darwin?) made these things called... HAND TOOLS! Approximately 92.125% of the "accidents" people have with assembling guitars comes from trying to overpower all obstacles with mass amounts of torque, BTU's and whatnot. Pickguard stuff is soft, you use a keyhole saw and a hand drill and it's almost done, finish with a metal file and rattail rasp. Of course you CAN hunt squirrels with a machine gun and iron your shirts with a steamroller, drive your McLaren to the store for a jar of peanut butter, but behind your back everyone is laughing at you.

 

[AutoBat]

I made an extra hole for a tone knob with a pair of scissors, opened up, applied in a rotating fashion until it was the right size.
At the time I didn't own a drill, or really any hand tools, aside from 2 screwdrivers & a hammer.

 

[Cagey]

I don't hunt squirrels with anything, they come to me and hope I don't twist their little heads off by hand instead of feeding them. Steam rollers are for those with much more hair than I have. If anyone laughs at my mythical McLaren, I say let 'em laugh while I spit on their all-too-real Ford Escorts. The day I'm so whacked out of my head that I start cutting pickguards out with handsaws and finishing the edges with files is the day I get back to my psychiatrist and ask what sort of adjustments I need to my meds. There are people out there who'll make perfect pickguards for you and clean up the mess afterward for not much more than what the raw material costs. Unless you want something that's otherwise unobtainable, why in the world would you mess with such a thing? That's like growing your own cows so you can have beef broth. Not that there's anything wrong with that as long as you're set up to do it, but it doesn't make a whole lotta sense for one-offs.

 

[Cagey]

I made an extra hole for a tone knob with a pair of scissors, opened up, applied in a rotating fashion until it was the right size.
At the time I didn't own a drill, or really any hand tools, aside from 2 screwdrivers & a hammer.

I used to do things like that for the same reason - lack of tools. You do what you gotta do. I eventually learned that tools could save me money, and as a side effect allowed me to do a lot more than I could before, or at least the same thing multiple times. I found out early on that It's pretty rare where tools actually cost you anything. The only thing you have to do is evaluate your ability to use them, and if it's there, the tools are probably pretty close to free the first or second time you use them relative to paying somebody who's already figured that out.