4 Conductor Hook-up Cable Capacitance Effects on Pickup Resonant Frequency

[Mike Sulzer]

... I think the C of the pickup changes when you wire it in parallel -- the inductance definitely does.

The C of two pickups in parallel is twice that of one. But sine the cable C is still dominant, the major effect is from the halving of the inductance and so the resonant frequency rises.

[salvarsan]

From what I've seen, some of the "vintage" braided wire can have extremely high capacitance. Maybe it's infested with some sort of mould that has a dielectric constant of 20.

It was the cheapest Fender,et.al. could find, turned out to be phone company surplus.
Technically, it was a PVC insulated tinned multistrand with a braided cotton outer jacket that
got a sodium silicate treatment to retard fire and prematurely wear out wire strippers.

@ScottA
Tefzel (a.k.a. PVDF) is piezoelectric so be careful how much and where you use it.
Google

[ScottA]

@ScottA
Tefzel (a.k.a. PVDF) is piezoelectric so be careful how much and where you use it.
Google

salvarsan,

Scared me for a second there...

Tefzel is ETFE, not PVDF. PVDF is "Kynar".

I can't imagine the insulation would be piezoelectric in a wire billed as "aerospace grade".

Scott

[salvarsan]

Tefzel is ETFE, not PVDF. PVDF is "Kynar".

Sorry, my bad. Signature at the end applies.

The dielectric constants are indicative.
PVDF -- 8.5
mylar -- 3.3
ETFE -- 2.5
Teflon -- 2.0

[RedHouse]

All of this is (very) "old news", specially the stock 4-cond capacitance problem, and the separation of signal ground from shield ground, but nice write-up (and graphics).

If I may ask, why all the focus on Zexcoil pickups? (almost smacks of an "Info-mercial"), normally one might expect to see results of cable testing utilizing the most common formats encountered.

[David King]

I've been using teflon insulated, Ag plated, stranded 4 conductor wire for a while. I like it because it's consistent with my hookup wire and it's really easy to solder. Is it supposed to sound better too? I have no idea what a lower dielectric constant means, is it better for low level music signals over short lengths? I find that hard to believe when most guitar cables are such garbage to begin with.

[David Schwab]

and the separation of signal ground from shield ground

They are going to get un-seperated as soon as the wire reaches the controls. Seems kind of silly to me. Ground is ground, and you only have one ground reference in a guitar.

I think he was talking about not grounding the shield, which would of course lower the capacitance, while of course removing the shielding affect.

If I may ask, why all the focus on Zexcoil pickups? (almost smacks of an "Info-mercial"), normally one might expect to see results of cable testing utilizing the most common formats encountered.

Because he makes Zexcoil pickups? This was obviously discovered while testing his own pickups. If I were testing cables it would be with my own pickups.

[ScottA]

All of this is (very) "old news", specially the stock 4-cond capacitance problem, and the separation of signal ground from shield ground, but nice write-up (and graphics).

You're right, there is nothing earth-shattering here. I was quite surprised at the difference between the two cable vendors, though. Also, while I understood the physics driving the capacitance effects, I didn't expect the effect to be so pronounced in such a short run. So, it took me by surprise, and I'd be willing to bet a lot of people making and using 4 conductor humbuckers hadn't fully appreciated the implications - which is why I thought I'd share it.

I do think the effect of the "inter-coil" capacitance (which is really between two sets of three coils in my stuff) is interesting, and the fact that it sets up that "notch" (see post #8) is noteworthy.

If I may ask, why all the focus on Zexcoil pickups? (almost smacks of an "Info-mercial"), normally one might expect to see results of cable testing utilizing the most common formats encountered.

David covered that. But, this is basically a chronicle of my investigation into an out of control event on one of my products.

[Mike Sulzer]

and I'd be willing to bet a lot of people making and using 4 conductor humbuckers hadn't fully appreciated the implications - which is why I thought I'd share it.

Nor so sure the implications are all that much. Add the guitar cable capacitance, and the pickup has very little response at such high frequencies; nor does the guitar speaker.

[ScottA]

Nor so sure the implications are all that much. Add the guitar cable capacitance, and the pickup has very little response at such high frequencies; nor does the guitar speaker.

I can hear it. I just clipped the grounds on an install I had done before this, a guitar that was bothering me as being a little too dark (a PRS SE EG that I picked up for $230, so I figured that was just the sound of inexpensive wood), and it was one of those "taking the blanket off of the amp" kind of moments. That guitar sounds really nice now.

Every little bit you can get helps in the never ending quest for tone.

[RedHouse]

...Because he makes Zexcoil pickups?...

Ah, I didn't see that (at first) in his auto-sig.

I know it seems silly to you David, we've had that discussion, let's not go back there.

[LtKojak]

a guitar that was bothering me as being a little too dark (a PRS SE EG that I picked up for $230, so I figured that was just the sound of inexpensive wood)

I have a PRS SE EG too, and it's my main "strat".

I had David Plummer aka Zhangliqun, maker of Zhangbucker p'ups wind me a Custom strat set with three different polepiece spreads, based on his "refin"set specs but with a 5/2 bridge p'up.

Nothing about this guitar sonds "inexpensive". Also, most people that had the opportunity of playing it, think it sounds like a million bucks! Me included.

Anyway, being a 25" scale, it's not as "snappy" as an all-maple strat, but to be able to hear a difference, you have to A/B it.

HTH,

[Mike Sulzer]

I can hear it. I just clipped the grounds on an install I had done before this, a guitar that was bothering me as being a little too dark (a PRS SE EG that I picked up for $230, so I figured that was just the sound of inexpensive wood), and it was one of those "taking the blanket off of the amp" kind of moments. That guitar sounds really nice now.

Every little bit you can get helps in the never ending quest for tone.

That does raise the resonant frequency with the cable a bit. i wonder if there is more to it than that?

[David Schwab]

so I figured that was just the sound of inexpensive wood

No it's the sound of those dark sounding pickups. I've swapped out pickups on those guitars a few times and they sounded a lot better.

[Joe Gwinn]

For background, I looked up the Zexcoil patent, US 7,989,690. The front is mostly legal boilerplate, trying to cover every possible variation, but there is lots of technical detail and rationale in the patent.