Guitar shielding/Pup Potting

Re: Guitar shielding/Pup Potting

Bezmotivnik said:
Different stuff, apparently.

The OEM stuff here shows in the Ks.
Click to expand...

I just looked at a friend's site and his experiments with the paint.

To judge from his measurements, this stuff is hugely more conductive than the OEM cavity paint I've recently tested.

On another forum, it was asserted that for shielding, high conductivity was not needed in the paint used, any conductivity was adequate.
 
Re: Guitar shielding/Pup Potting

Bezmotivnik said:
Different stuff, apparently.

My multimeter told me it was just barely able to pass electricity.

When you jab the probes into yours, what sort of DCR are you seeing?

The OEM stuff here shows in the Ks.
Click to expand...

The meter zero's out just like touching the probes together. The OEM stuff is often applied so thin there is no possibility of good conductivity.
 
Re: Guitar shielding/Pup Potting

TheArchitect said:
The meter zero's out just like touching the probes together.
Click to expand...

Mark (see link, above) couldn't quite achieve that.

The OEM stuff is often applied so thin there is no possibility of good conductivity.
Click to expand...
It certainly is thin, but I suspect it is indeed different paint. In any case, what I've read is that for shielding, high conductivity is not important compared to continuity and continuous coverage -- if you're not trying to use the surface as chassis ground. If that's the case, you do need a metal foil.

There's some speculation that by using paint with lower conductivity, the loss of high frequencies may be lessened, but I haven't seen any persuasive theory or evidence of this offered.
 
Re: Guitar shielding/Pup Potting

Bezmotivnik said:
I just looked at a friend's site and his experiments with the paint.

To judge from his measurements, this stuff is hugely more conductive than the OEM cavity paint I've recently tested.

On another forum, it was asserted that for shielding, high conductivity was not needed in the paint used, any conductivity was adequate.
Click to expand...

There's a small flaw in his measurements......his finger!! The numbers will change, should go lower, without his finger on any of the probes (the last 3 shots). When doing measurements like this, keep your hands/fingers off anything that is part of the circuit. Use alligator clips on the ends of the probes if you have to.

Since he said he had to put the wire that connects all the pots together back on, that tells me that that paint is not conductive enough for that particular purpose. On the pickguard use the copper tape, heavy duty aluminum foil, or the Callaham pickguard shield.

Is it me or don't his numbers seem a little high for a shielding job like that? My numbers are like 0.02 with an all aluminum foil shield (with the meter on the diode setting - only setting on my meter that reads 0.00 with the probes touching).
 
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Re: Guitar shielding/Pup Potting

ErikH said:
There's a small flaw in his measurements......his finger!!
Click to expand...
Makes no difference. Try it. You measure DCR through path of least resistance.

Since he said he had to put the wire that connects all the pots together back on, that tells me that that paint is not conductive enough for that particular purpose. On the pickguard use the copper tape, heavy duty aluminum foil, or the Callaham pickguard shield.

Is it me or don't his numbers seem a little high for a shielding job like that? My numbers are like 0.02 with an all aluminum foil shield (with the meter on the diode setting - only setting on my meter that reads 0.00 with the probes touching).
Click to expand...
He's running all his measurements through the paint, not foil. The paint doesn't have the conductivity of foil. Not even StewMac magic paint.

We're talking about shielding here, not chassis grounding (see my earlier message).
 
Re: Guitar shielding/Pup Potting

ErikH, where do you buy your caps from?

I want to change to a 0.47 one, but no idea where to order them from.
 
Re: Guitar shielding/Pup Potting

lickinice said:
ErikH, where do you buy your caps from?

I want to change to a 0.47 one, but no idea where to order them from.
Click to expand...

You can buy premium caps at www.wymoreguitars.com or from Bada Bing, a member here who is a Duncan dealer also, I just don't have his website handy. Allparts sells them, so does Mojo Musical Supply. Or you can buy small, cheap ceramic caps at Radio Shack.
 
Re: Guitar shielding/Pup Potting

Jeff,

Does the maker of the caps matter? or just the values?
cause they have oil film etc etc what have you. do those matter?

What should I be looking out for ?

For tone OR volume?

This are for strat/teles
 
Re: Guitar shielding/Pup Potting

lickinice said:
ErikH, where do you buy your caps from?

I want to change to a 0.47 one, but no idea where to order them from.
Click to expand...

Aside from the place that Jeff pointed out, instead of ceramics from Radio Shack, get the green "chicklet" ones instead. They're a better cap than ceramics. You want .047 for a tone cap though. 0.47 is too big. ;)
 
Re: Guitar shielding/Pup Potting

Are those the only caps I can use?

Can I get them from my local electrical hardware store?

What should I be looking out for when getting caps?
 
Re: Guitar shielding/Pup Potting

You can use what you can find if you have a hard time locating them. As long as you use a .047 or .022 cap for the tone control you're fine.

If you're wanting circuit protection cap (like on guitarnuts.com), then you want a 0.33 (bigger than the other too) with a 400V minimum rating. If you are wanting a tone pot cap, then ignore this part for now.
 
Re: Guitar shielding/Pup Potting

I use graphite paint which I make up myself so I can control the density of the solids. I also use copper tape for some functions and ordinary household foil on pickguards stuck with photomount spray adhesive.

Pickups are potted in a vacuum chamber using a blend of low melting point paraffin wax and anhydrous lanolin to produce an acoustically dead sludge.

The capacitance effect of the cavity screening is virtualy negligible; more significant is the use of screened cable. Discrete cable used within a screened cavity wil result in a HF loss which is barely detectable and most likely masked to auditory perception by the many other changes.

Where screening can cause significant loss of top end response is when the coil is wrapped in screening foil and the signal path is taken from the outer windings of the coil. The coil output then "sees" the capacitance across its terminal formed by the screen, which is connected to ground. Reversing the terminals of the coil eliminates this by making the outer windings part of the ground/return circuit. This is inherently less noisy as the outer windings form a screen in themselves but because there is a null capacitance across two conductors connected to the same path (in this case the ground path) there is no capacitance effect to sap the HF component of the signal.
 
Re: Guitar shielding/Pup Potting

Okay, I will check out my local hardware store.

Any difference with ceramic and what other kinda capacitors avaliable?
or should i buy a dozen varieties and try? lol
 
Re: Guitar shielding/Pup Potting

bada bing, i'm interested in buying some matched/individual pickups.

Any way you can send me a catalogue?
 
Re: Guitar shielding/Pup Potting

lickinice said:
Okay, I will check out my local hardware store.

Any difference with ceramic and what other kinda capacitors avaliable?
or should i buy a dozen varieties and try? lol
Click to expand...

Just get some in those few values and have it with experimenting. Get some .033, .018, maybe a .015 and see what you like. Rather than soldering them in, just clip them in with a couple alligator clips to hold it in place, listen to how the tone control works, rinse and repeat.
 
Re: Guitar shielding/Pup Potting

It's just a saying. Rinse and repeat meaning to do it again like it says on a shampoo bottle. :) What I was meaning is when you test out one cap, take it out, put another one in and test it out (hence the saying rinse and repeat). :)
 
Re: Guitar shielding/Pup Potting

Oh, i almost fainted when you said rinse, thinking 'why would someone wanna rinse an electrical component'

I will do as you have mentioned, I'm thinking of building a few guitars, it'd be good to start experimenting with caps and such.

Guitars here are expensive and making my own is probably better value as i can get it to exact specs. Maybe even build to sell.
 
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