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Hey, all you experienced electric builders, I have a question, please. I'm reading and preparing to build my first electric and have a question concerning grounding and shielding.   I understand on a guitar using single coils that all the cavities must be shielded and everything grounded.

I'm going to build a semi-hollow body based on the Gibson CS-336. It will have two Gibson '57 classic humbuckers with metal covers. I understand how to ground everything. My question really concerns shielding. What shielding is necessary, if any, with this type of set-up?

Thanks,
Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Two humbuckers won't require any shielding. Some people paint the cavaties with Shielding paint anyway. The covers should also act as "shields". I also think the p/u's sound different/better with out the covers. Some people actually wrap the pickup with copper foil that S.M. sells. If you do this you must be careful you don't break any of the wires. I don't use the foil wrap. You s/b fine as long as you remember to run a ground wire to the saddle/bridge/string t/whatever.

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Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

Hey Ron,

I shield with self-adhesive copper foil in the cavity and also earth each component to a common star point rather than loop. I got my foil from WarmothWarmoth. This stuff is easy to fit as the adhesive is conductive which means you can stick pieces over the top of each other to cover the hole cavity pushing the foil into corners to conform but it will act as one piece.

What I mean by common star point for the earth is that you run your earth wire from the tailpiece to a copper star washer screwed into the shield within the cavity. All components are then earthed back to this common point. Makes for a very quite, very reliable guitar.

Cheers

Kim

Shielding is pretty much always optional; you want it in single coild guitars, because they'll hum like mad otherwise (well, mostly), but a fully shielded set will sound less dynamic than an unshielded one.

I don't tend to shield my humbucker guitars, just ground them properly (star, usually). I'll see what I do with my P-90s.

I agree, no real need to shield especially with buckers but I did on my last anyway and was very happy with the results. It is just soo quite now until you hit a string and I think star earthing is the only way to go oh and nice new cts pots is a big help to.

Cheers

Kim

Have a look HERE Ron, lots of good info.

cheers

Kim

Thanks, guys. That's pretty much what I had understood. Kim, I appreciate the star washer explanation. I had seen reference to star grounding to eliminate ground loops, but nowhere did they actually say what that meant. Sounds good.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Sorry, guys, but you're confusing electrostatic noise with electromagnetic noise. All electric guitars need shielding against electrostatic garbage getting in whether they have single coil pickups or humbuckers. I wrote extensively about this in Bass Player Magazine about fifteen years ago, and I'll try to dig up the article and post it here.

A little test:

If the buzzing changes when you touch one of the grounded metal parts of the guitar, that's electrostatic noise, and it can be cured by shielding.

If the noise changes when you turn one way or another relative to your amp, then you've got electromagnetic noise and that is only cured with some form of humbucking with the pickup design. No amount of electrostatic shielding will help this.

The issue of shielding pickups and changing the sound is two fold. If the shielding is too close to the pickup coils, there can be a bit of stray capacitance that cuts highs...but this is very rare. The material and thickness of the shielding can also change the tone because of eddy currents that change the pickup's inductance. If you choose to use humbuckers without covers, then shield the pickup cavities...which is not a bad idea anyway.

I've seen quite a few shielding jobs where the tech failed to ground the shielding via a star grounding wire. This actually makes the noise worse as the large conductive plane acts as a hum and buzz antenna and couples capacitively to any hot signal carrying wires.

Thanks, Rick. So, on a semi hollow body where the controls are not actually in an isolated cavity is there a way to shield them or do I need to design a seperate control cavity into the body?

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

We paint the inside as much as we can with conductive paint before we glue the backs on.   Note that Gibson used to enclose their volume and tone pots in shielding cans in 335's. They used to do a great job of that.   They also had brass stamped boxes inside Les Pauls.   Then there were the dark years when they cheaped out...

Thank you.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

I've been under the impression (perhaps incorrectly) that hotter pickups require shielding as they are more sensitive to electrostatic interference.(?)

Also, the type of shielding that I have seen is "electro-dag", which is basically a type of metallic paint that is brushed into the electronics & pickup cavities.

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http://www.PeakeGuitars.com

Hotter...

Well, that brings up a Pandora's box of issues.

Higher impedance, maybe, but higher impedance does not automatically equate with hotter, though if you keep the bobbin and magnetic structure the same and wind more turns of the same wire, you'll increase both the impedance and the voltage output. But you could just wind the same number of turns with finer wire and not have any more output AND have a higher impedance.   

The commonly available ElectroDag is what Stew Mac sells (at a pretty reasonable price), and it is carbon based. You can get nickel and silver based shielding paints, too.

Sounds like a great project, I've always loved the CS336.



Just a note here...if by chance you're going with nylon or graphtech
saddles, then you'll need to ground the strings via the tailpiece
instead of the bridge itself (those materials being non-conductive).



There are also some sound gurus who swear that a significant component of "that vintage sound" is 60 Hz hum, so YMMV.

"There are also some sound gurus who swear that a significant component of "that vintage sound" is 60 Hz hum, so YMMV."

If that is not in jest, then what a load of crap! That's like saying that polio is a part of the good old vintage summertime fun.   

Hum was not as much of an issue in the 1950s when Strat, Tele, and even the famous humbucker pickups were designed. There simply was not as much AC wiring around, there were few dimmers, there were no personal computers, and guitarists didn't play at such high volume levels and they certainly didn't use cascading gain stages. Even a Fender Broadcaster was pretty noise-free in its day.   Still Gibson shielded their guitars very well then, and Seth Lover was annoyed enough by what hum and noise there was to design the humbucker...which he shielded like crazy.   The vintage sound did not include a lot of 60 Hz noise.   That's a relatively modern problem and it's not musical...in my opinion!

I suppose I could invent a 60 Hz hum inducer for digital recording systems and make a lot of dough, though...

[QUOTE=Rick Turner]

If that is not in jest, then what a load of crap! That's like saying that polio is a part of the good old vintage summertime fun.   

[/QUOTE]


I don't think so. Rick, Rick, Rick, there you go again. This thread was running along nicely, and I appreciate your responses, but this kind of response is what's causing the problems around here lately.   There wasn't nearly as much hum around back then, but there was hum. You don't have a clue as to whether some people think that sound should still be present or not. To me, a good analogy is the record album. Many people prefer the original sound of good old LP records, including scratches, to the artifical, electronically enhanced CD's. That's a fact.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

[QUOTE=Rick Turner]

If that is not in jest, then what a load of crap! That's like saying that polio is a part of the good old vintage summertime fun.   

[/QUOTE]

I'm apt to let the coarseness of the response slide because that line was comedic gold.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I am a little late in this thread, sorry.

Rick, do you use the carbon based shielding paint, the nickel or the silver one you mentionned?

Marc

No, there is no reason to switch. We use the carbon based stuff, too.   I used the silver paint many years ago because either the carbon stuff wasn't available yet or we just didn't know about it, and we did know where to get the absurdly expensive...but cheaper than making brass or copper boxes...stuff was to be found.

I suppose a case could be made for keeping the resistance as low as possible, but there's theory and there's what actually works fine, and the shielding paint from Stew Mac works just fine. We paint two layers...

OK as to hum as a part of the music...well 60 Hz is almost a perfect quartertone between Bb and B natural. Do you want a quartertone flat or sharp drone in your music?   To think that it belongs there is right up there in the absurdist camp in my book. And to use the example of LP records is to set up a "straw man". Audiophiles who love LPs love them not because of the flaws, and in fact they spend thousands of dollars to minimize those flaws by using exotic turntables, cartridges, and tone arms.   I should know because I have gear in the lower dollar range of the high end classic analog realm...Thorens, Grado, Hadcock tone arm, custom monoblock tube preamps, McIntosh power amps, Nelson Reed speakers, etc.   The reason some of us like vinyl is because the high end roll off is much more natural than you get with standard CDs or cassettes. However with SACDs and some of the DVD formats, digital is catching right up with analog and in certain cases is exceeding it. The use of faux pops and clicks on CDs is an effect, not an attempt to make the sound "better". It's an artifice trying to sound Old Timey. It's like singing through a megaphone and pretending to be Rudy Vallee.

My pal Kavi Alexander of Water Lily Acoustics was one of the last hold-outs releasing audiophile vinyl, and the stuff sounds incredible. He's now releasing CD's in the Sony hi-def CD format and he's recording on very high sample rate digital gear. Why? Because it does a better job of getting the music across.

There are a lot of vintage electric guys who are anal compulsive, obsessive compulsive, and just plain nuts. They've managed to convince a lot of people that features like hum are authentic and soulful. Not even the vintage car racers run on vintage rubber, and they now have seatbelts in their vintage rides. I never heard a vintage electric guitar that didn't sound better with the hum and buzz gone.   The out of tune hum and buzz...

[QUOTE=Rick Turner]"There are also some sound gurus who swear that a
significant component of "that vintage sound" is 60 Hz hum, so YMMV."



If that is not in jest, then what a load of crap! [/QUOTE]



Allman Bros Live at Filmore (for one).  It's there, even on the original vinyl. 

The "sound" isn't created to make it sound better, just to make it more authentic to the original.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

If it's to be more authentic, then those espousing that bit of fruitcakery should live in houses and play in venues where the entire electrical environment is stripped back to the electrical distribution levels of 1955 when the earliest Teles, Strats, and Les Pauls were all practically brand new instruments. Those were the days before wide spread use of fluorescent lights, dimmers, wall wart power supplies, personal computers, transistors in any place other than Bell Labs, etc., etc., etc.   In those days rooms in the average house often had but one electrical outlet and one overhead incandescent light fixture.   In many cities, like Boston, there was still DC power distribution, and those using AC only gear had to use inverters...that's how my grandmother powered up her TV on into the early 1960s. To be authentic one would not use multiple gain stages and overdrive amplifiers that hugely exacerbate the problem with all that hum. One would not record to anything other than an Ampex 350 series tape recorder.

Hum as a part of the sound is about as authentic as a Civil War re-enactor wearing Jockey shorts under his repro pants. Let's call it "Fauxthentic"...