Potted vs. Unpotted: Harmonic content, Swirl, Openness, Pinch Harmonics

rewihendrix

Member
Messages
396
I don't know about the strictly mechanical versus the electronic/electro-mechanical aspects.

I tend to think that microphony is an artifact and the real (primary?) driver is the fact that wax potting displaces the air between the windings with wax, a higher dielectric constant material, causing an increase in distributed capacitance. But, I can't discount the mechanical aspect out of hand.
I'm not quite sure how this would work. Are you saying is that the shielding on the copper wire has failed?
 

Zexcoil

Vendor
Messages
5,787
I'm not quite sure how this would work. Are you saying is that the shielding on the copper wire has failed?
No, the shielding is intact. There is space between the windings. They're not perfectly layered, and even if they were there would still be space in there - you can't pack things with a circular cross section to zero void volume.

When the wax displaces the air in all of that volume, the capacitance goes up, as it becomes easier for the windings to cross-talk to each other.
 

HayekFan

Member
Messages
1,526
I don't know about the strictly mechanical versus the electronic/electro-mechanical aspects.

I tend to think that microphony is an artifact and the real (primary?) driver is the fact that wax potting displaces the air between the windings with wax, a higher dielectric constant material, causing an increase in distributed capacitance. But, I can't discount the mechanical aspect out of hand.
That's a good point. I wonder if anyone has measured how the capacitance changes when you pot a pickup.

I will say that a simple change in C doesn't seem like it could explain all of the complex tonal benefits that people ascribe to unpotted pickups. Having less distributed capacitance would shift the resonant requency upward giving you a brighter pickup, but would it give you swirl etc?
 

rewihendrix

Member
Messages
396
No, the shielding is intact. There is space between the windings. They're not perfectly layered, and even if they were there would still be space in there - you can't pack things with a circular cross section to zero void volume.

When the wax displaces the air in all of that volume, the capacitance goes up, as it becomes easier for the windings to cross-talk to each other.
How can the windings cross-talk to each other if the shielding is intact?

Is the capacitance not a function of the resistance due to the length of the wire coils, rather than cross talk?
 

Zexcoil

Vendor
Messages
5,787
How can the windings cross-talk to each other if the shielding is intact?

Is the capacitance not a function of the resistance due to the length of the wire coils, rather than cross talk?
Adjacent windings act like the plates of a capacitor, with the material between them the dielectric.

So yes the total length of wire matters, as does the shielding material, among other things.

search: distributed capacitance of a coil
 

rewihendrix

Member
Messages
396
Adjacent windings act like the plates of a capacitor, with the material between them the dielectric.

So yes the total length of wire matters, as does the shielding material, among other things.

search: distributed capacitance of a coil
Ah I see, thanks for that
 

HayekFan

Member
Messages
1,526
Yeah, but hopefully, though clearly not always around here, focus on things that can actually impact the sound. The wax simply cannot.
Well, Lindy Fralin switched from bees wax to paraffin because he said the paraffin didn't darken the top end as much. If the two waxes have different dielectric constants then it seems feasible there could be tonal differences.
 

71strat

Member
Messages
9,360
I had Tom Holmes wind 2 sets of his unpotted Alnico II and reverse neck magnets.

Unpotted for me.
 

Zeppe

Member
Messages
323
I tend to think that microphony is an artifact and the real (primary?) driver is the fact that wax potting displaces the air between the windings with wax, a higher dielectric constant material, causing an increase in distributed capacitance.
This is what I have always assumed to be correct. Guitar pickups are high impedance devices, so they are susceptible to conductive loads. An analogy for wax potting is running your guitar through a longer guitar cable. What happens when you pot a coil is that you solidify the windings so they can't vibrate, otherwise known as "microphonics".
Part of the PAF and P90 sound IMO is microphonics.


When you mount a metal pickup cover, you are introducing eddy currents.
 

edgewound

Member
Messages
5,725
Unpotted for me as well.. The Zhangbuckers I use are that way and they're quite unbelievable tone wise...
Zhangbuckers also have assymetrical coils, which greatly influences the tone, probably way more than non-encapsulation.
 

splatt

david torn / splattercell
Platinum Supporting Member
Messages
25,780
Having less distributed capacitance would shift the resonant requency upward giving you a brighter pickup, but would it give you swirl etc?
..... nothing whatsoever to do with "swirl", as i understand "swirl".
 

MrKite89

Member
Messages
1,679
Unpotted pickups are a little more microphonic, and that's a good thing to me: more organic\less sterile sound, but if you play with tons of gain always they could be hard to control...
 

Deed_Poll

Member
Messages
3,088
Depending on what kind of pinched harmonics you want you might consider an out-if-phase neck pickup. If you wanted Zakk Wylde style squealing high gain stuff probably not, but seeing as you're considering unpotted pickups I'm guessing that's not the case.
 

Polynitro

Member
Messages
23,616
i have unpotted novaks and they sing and are more alive than any other pickup.
but this comes at a price: gain!
 




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