Pole piece design question....

[bchaffin72]

Secifically Fender style single coils.

On a traditional pickup, the pole pieces are the magnets. On other styles, generally the cheaper ones, they are steel slugs with a wide magnet(or sometimes 2 skinny magnets) underneath.

And on a tele bridge pickup with a baseplate, there is usually tape masking the bottoms of the poles to isolate them from the baseplate and keep them electrically/magnetically separated. But the ceramics, by nature, have all the poles connected by the magnets.

The test pickups I have built so far fall in the middle. Steel slugs, but the magnets are individual and the poles remain separate from each other.

I'm just curious what differences these things make to the performance of the pickup, intentional or otherwise.

 

[copperheadroad]

Ceramic magnets are not conductors like Alnico so they can touch the poles .
I find using Ceramic magnets in this form you get a kind of compressed tone .

 

[bchaffin72]

Ceramic magnets are not conductors like Alnico so they can touch the poles .
I find using Ceramic magnets in this form you get a kind of compressed tone .

Thanks. That does make sense. So as far as the poles are concerned, they're still separate, since the ceramic won't conduct between them anyway.

 

[bchaffin72]

What I currently have on my homebuilt test pickups(it's changed a couple times) are individual neo button magnets the same diameter as the pole pieces, one for each pole. So even though they are strong, they act through the poles rather than being more directly under the strings.

From what I was reading, Neodymium is not very conductive(1/50th of copper), but I imagine one would still want to isolate if using a baseplate.

 

[Tatercaster]

What I currently have on my homebuilt test pickups(it's changed a couple times) are individual neo button magnets the same diameter as the pole pieces, one for each pole. So even though they are strong, they act through the poles rather than being more directly under the strings.



From what I was reading, Neodymium is not very conductive(1/50th of copper), but I imagine one would still want to isolate if using a baseplate.

You'd probably want to immobilize the magnets as well, perhaps with super glue or epoxy.

 

[bchaffin72]

You'd probably want to immobilize the magnets as well, perhaps with super glue or epoxy.

I do that anyway, just to make sure they stay in place, otherwise they will pull right to each other if the pickup gets bumped and they shift.

 

[bchaffin72]

My other point of curiosity is what are the potential performance differences between having the pole pieces as magnets vs having slugs magnetized from underneath?

I know with the cheaper pickups the main reason for the ceramic/slug combination is cost. Same for most of them using one piece plastic bobbins. I'm just wondering if there are other implications, good or bad, in that type of design.

 

[copperheadroad]

A good sounding pickup using this design is the MIM fender Strat & Tele pickups .
& you don't need to isolate with a baseplate .the ferous baseplate on a tele is to warm up the tone a little & possibly help with noise but it is not necessary.

 

[bchaffin72]

I know the baseplate isn't necessary and plenty of tele bridge pickup don't have them. My Squier pickup doesn't since it's got that big ceramic bar underneath. Now I have seen ceramic pickups with a baseplate, but it looks rather ungainly as there is a big, magnet thickness gap between the baseplate and the bobbin.

What I mean, though, is if you are using a baseplate and the poles or magnet material ARE conductive(even a little) you should still probably insulate the poles from the plate.

 

[copperheadroad]

compare the 2 . Ground the poles & insulate between the poles & the plate to see if it reduces any hum/noise Fender always used tape between the plate & the poles & taped the top of the poles from the cover on a tele neck pickup .

 

[bchaffin72]

Well, at the moment, I don't have any baseplates or an easy means to fabricate them. What I've built so far has been from household stuff, salvaged wire, and surplus store magnets.

I have some tele bridge pickup kits and wire in the mail to build something more proper and usable.

I'm mostly looking for info on different design choices and why, cost and otherwise, that they get made and what benefits and drawbacks are to different designs. Certainly ceramic magnet/steel poles can sound good, but is that decision still mostly about cost, or could there be other reasons for using it rather than the traditional Alnico poles on some pickups? Or, am I just overthinking the whole thing??

 

[Derek Kiernan]

The poles should be grounded, so really, it's the coil that should be kept from touching the poles.

 

[copperheadroad]

The poles should be grounded, so really, it's the coil that should be kept from touching the poles.

Poles were never grounded from any fender Pickup
one the other hand poles on a humbucker are grounded

 

[bchaffin72]

so really, it's the coil that should be kept from touching the poles.

I know that's part of why they dipped the old bobbins in laquer before winding, as insulation. I disassembled a more modern pickup and it had a wrap of electrical tape around the poles to keep the wire from direct contact.

Poles were never grounded from any fender Pickup

Never seen any that were. On most, outside of a tele bridge pickup with baseplate, there'd be nothing on the pickup to ground them to anyway.

 

[Derek Kiernan]

If the poles read in continuity with the coil, then you effectively have shorts, and you're "grounding" the poles to the signal instead.

 

[bchaffin72]

I found this on the Seymour Duncan website:

"Generally speaking, individual Alnico magnet pole pieces deliver bright, tight tones, while steel pole pieces sound fatter and looser. That’s one of several reasons why Fender® guitars with their magnetic pole pieces tend to sound brighter than Gibson® guitars with their steel pole pieces."

However, that doesn't seem very useful, as their are enough other differences between Gibson and Fender pickups to know whether the pole piece construction is a larger or smaller factor in the overall sound.

 

[Derek Kiernan]

Steel poles are magnetically "softer" than Alnico poles, but also typically have higher eddy current potential than Alnico. Steel poles can be more responsive to tonal and dynamic changes than Alnico, but if eddy currents kill the highend, then you could end up with a less tonally flexible pickup. Steel poles also typically have considerably higher permeability, so with the same coil, they have greater inductance, which often translates to somewhat higher voltage output but less highend, and a lower resonance that establishes the coloration in the highend.

The magnetic design has to be different, as well, so the return path isn't the bottom of the pole, but the opposite pole of the permanent magnet attached.

 

[bchaffin72]

Thanks. Makes a certain amount of sense, since the magnets are acting more indirectly, via steel poles, rather than directly by BEING the poles.

What I've been playing around with is a 9.3k coil, 42 gauge wire salvaged from two cheap Squier pickups, steel poles also salvaged from an old Squier pickup, and a small neo button magnet for each pole.

According to what people say of the sound sample I did, it has nice crunch and an "interesting" clean sound.

https://soundcloud.com/bchaffin72/4a-1


The parts I have in the mail have A5 magnets, a steel baseplate, and I'll be using 43 gauge wire for the builds.

 

[copperheadroad]

Alnico rods tend to stay cleaner than pickups with steel poles
Make one of these
http://www.skguitar.com/SKGS/sk/winding2.htm

 

[bchaffin72]

Make one of these
http://www.skguitar.com/SKGS/sk/winding2.htm

Interesting. I do have another cheap set of ceramic strat pickups laying around that could be guinea pigs.