tone dulling potting....

[Possum]

Anyone have any ideas on a potting substance that would increase the inductance/AC resistance and dull down an overly bright pickup coil? I want to try to simulate an aged coil somehow. I have a famous blues player's '63 strat guard here and after measuring his pickups its real obvious that somehow the magnet wire in his pickups has aged and the ohms per foot have noticeably increased, either that or the wire they had back then was less pure than what we get now, or has oxidized somehow. Even the cloth covered hookup wire in his guard has measurable resistance, a foot of it measure about 1.5 ohms.

[David Schwab]

That's interesting. I have a friend with a early 60's Strat, and the pickups sure do sound different. The magnets don't seem much weaker either, but the pickups are real warm sounding.

Here's something to try... I've been wanting to mess with this stuff myself. Rust-oleum sells magnetic paint. It seems to be suspended iron or something similar in a paint binder. I'd bet spraying that on the wound coil would raise the inductance.

Or maybe conductive carbon shielding paint? I wonder what potting in that would do?

[Possum]

magnets....

I just rewound the neck pickup in this thing after Fralin's shitty job of using the wrong kind of wire (poly) and winding it in the wrong direction, you'd think he'd known better. Anyway, alot of the tone is coming from the magnets too, they are warmer sounding but they are definitely alnico 5 up the 1000+ gauss range even after all these years. I thought about potting in steel impregnated wax but really its not going to penetrate the coil, it'll only end up on the outside where effect would be minimal. Whats that paint called?

[David Schwab]

Actually the one I was thinking of was made by Krylon. I saw some in a hobby store in a spray can. But Rust-olium makes a magnetic primer for walls.

I was thinking of this one:

Krylon Magnetic Paint

[R.G.]

This will probably just expose my ignorance, but why not do it the simple way? Put a resistor in series with it and a small cap across it. The resistor will lower the inductance Q just like if the wire was higher resistance, and the cap will reduce highs just like a higher coil capacitance or loading (which it is).

Plus you can season to taste.

[Rosewood]

Not to hi-jack here but I wonder if this krylon could replace the expensive shielding paint?
As far as the pickup I potted one of my first single coils in shellac and it dulled it down, I didn't like it. Don't know if the shellac was not dried good when I tested but I have not heard that pickup in a long time, maybe it's different now.

[Possum]

hmmmm.......

I don't think a resistor would have the same effect as loading the magnetic circuit with metal, eddy currents. I think those magnetic paints probably are ferrite which won't load the circuit either. I started another post on, is it possible to soften alnico magnetically? That stuff is awful hard yet the metals that make it up aren't hard metals. I know that SRV wrapped his pickups in copper tape yet if I do that I don't measure any change, but I didn't ground it either...

[soundmasterg]

Why not pot the pickups like they were originally? Then you can maybe adjust the brightness back with some careful pot selection? Actually it may be a good idea to measure the pots...maybe they've drifted a lot?

I heard AC Porter's '64 Strat last wednesday at the jam and that is the best one I've ever heard and it wasn't at all bright and glassy. That era must have been ok then, although I've played Robert Cray's #1 Strat too and its very bright and has somewhat weak pickups compared to most Strats. I seem to remember his being around '63 but I don't recall for sure. Its been about 8 years since I played that one, and only played it for a couple minutes at the 12th fret when it was in for a fret job.

Greg

[Possum]

nah....

Potting won't change the AC resistance, which is what I'm trying to do. This guy's pickups from '63 aren't shrill at all even the bridge which is 6.5K stays away from icepick. I think the magnets are alot of it, but I think the aging wire has oxidized over time increasing the resistance in the wire, or the dielectric is breaking down and taking the edge off. I do know new strats from any vintage era were pretty shrill, just go to Youtube and watch Gene Vincent videos for an example of that.....

[mick]

Maybe....................?

What about the ally shield that sits under the pickguard ?? you tried the pickup in the guitar or are you just relying on the extech readings??

Mick

[rocket]

why don't you use thinner wire with thicker insulation? like double buillt 43?

[R.G.]

I don't think a resistor would have the same effect as loading the magnetic circuit with metal, eddy currents.

Still, it's an awfully quick and easy test to perform, right?

Eddy currents are the electronic equivalent of transformer loading on the coil, so they do look like a resistor. The only reason I don't insist that a resistor is equivalent is because of the highly distributed nature of the resistance/capacitance of a pickup coil. That's why I said that I was probably exposing my ignorance.

If the aging of a pickup is because of the wire oxidizing, a series or parallel resistance is going to be a pretty darned good emulator.

This is exactly the kind of question that I'm going to be attacking with the pickup test bed - what kind of imperfections you can introduce where to get the same effect.

[Joe Gwinn]

Anyone have any ideas on a potting substance that would increase the inductance/AC resistance and dull down an overly bright pickup coil?

Nothing will change the inductance except more wire or a better magnetic circuit.

Nor can a coating change the AC resistance. A loop of copper wire would around the magnets would do it. A small multiturn coil laid down first, and connected to a low-ohms pot, would allow the degree of shorted-turn effect to be varied to suit.

I want to try to simulate an aged coil somehow. I have a famous blues player's '63 strat guard here and after measuring his pickups its real obvious that somehow the magnet wire in his pickups has aged and the ohms per foot have noticeably increased, either that or the wire they had back then was less pure than what we get now, or has oxidized somehow.

A little bit of moisture trapped in the windings will dull the sound. I bet this is why. The test is to see if baking at 100 C causes the sound to sharpen. This was why Leo invented wax potting.

Even the cloth covered hookup wire in his guard has measurable resistance, a foot of it measure about 1.5 ohms.

That cannot be right. I'd bet that the ohmmeter didn't make good contact.

[DoctorX]

Joe,

I am working on an idea, but I need some clarification first. How would moisture trapped in the windings change the characteristics of the coils without ruining the entire coil? Wouldn't the moisture in an unpotted coil evaporate over time?

Thanks,

DoctorX

[mick]

Hmmmmm

Just dropped an ally guard over a pickup , it changed the ACR and the inductance...acr went up inductance went down , hmmmm , funny that..