pole piece thickness.... what should I hear?

[FunkyKikuchiyo]

Okay, so I always had a picture in my head of what different pole piece thicknesses did to sound, but I'm starting to doubt that. It was largely based on what I heard in other models, and I had decided that it added a sort of obnoxious honk. I'm realizing now that I'm probably hearing other elements of those designs - they tend to be over wound and all around just different animals. I'm debating doing some of my own experiments but since that is a bit of time and money I thought I'd farm the forum for ideas.

Anyone? I know Possum got some good reviews from VG on one of his models like that.

[Mike Sulzer]

Fatter pole pieces increase inductance, as does overwinding. Lower resonant frequency, less highs. I would also expect higher losses in the cores due to induced currents.

Okay, so I always had a picture in my head of what different pole piece thicknesses did to sound, but I'm starting to doubt that.....

[frankfalbo]

And don't forget the aperture. The window of string seen by the magnetic field is larger. If you're talking about .187 vs. .197 then it's a minimal part of the total equation, but in something like the Seymour Duncan Quarter Pound, it's a more substantial piece of the puzzle.

[FunkyKikuchiyo]

Fatter pole pieces increase inductance, as does overwinding. Lower resonant frequency, less highs. I would also expect higher losses in the cores due to induced currents.

This is part of the puzzle I'm having trouble with. I don't doubt that it increases inductance and some of my own experiments would verify that, but whether that darkening of the tone is the most pronounced element or not I'm not sure. I'm used to thinking of them as darker and more honky because that is what I hear in things like the duncan quarter pounder, but those are also wound hotter and possibly with thinner wire so I'm doubting those observations. I've heard some wider pole piece pickups that end up brighter and more present, and the dynamics seem to change significantly. Is that perhaps strictly because of the aperture, or something else?

[EtLa]

And for the same number of turns a fatter core (due to the thicker pole piece) increase the DCR and the inductance.

BTW I'm confused, are we talking about steel pole piece or magnet pole piece?

[FunkyKikuchiyo]

BTW I'm confused, are we talking about steel pole piece or magnet pole piece?

I hadn't given that any thought. For argument's sake, maybe we should think about both?

[kevinT]

Well, with steal screws you have a little more to think about.

Metal grade
Shaft diameter
Shaft length
Head shape and mass
Plating


These different features all affect tone.

[Possum]

...

Yes they are different, how to characterize the differences? Well I don't think I could even explain it. Just try it. Make two bobbins with equal coil heights, use fat poles in one and thin poles in the other, wind them the same and use the same wire. I use the fat poles in pre-CBS stuff and thin in CBS, but different magnet wire. The pre-CBS stuff sells way better. You can buy singles from StewMac or Mojo just to make one. In buckers yes it makes a difference too, early Patents have small heads compared to PAF era ones, I prefer the big heads and thats what I had made.

[FunkyKikuchiyo]

I guess there is no way around just trying it. Thanks for the help, though. With the stuff I'm working on I have some serious economy of space issues, so I was sort of hoping everyone would say "thick pole pieces sound horrible!"

Possum - I've lately been hearing a bit more high end and a bit more percussiveness. Does this sound anything like what you're hearing?

[Possum]

...

I don't make anything that uses the same wire with fat and thin magnets so can't say directly how they differ. Thin sounds sorta slushy to me and fat sounds more direct and present.

[soundmasterg]

Another wrench to throw into the puzzle is the Rickenbacker Toaster pickup. It uses some big pole magnets (I think they are 1/4") and is known for being balanced, but bright sounding. It typically uses about 7.5k of 44 gauge formvar also. They are certainly bright, but are kind of in between a Tele and a Strat soundiwse, having more bass than both, and not being as bright as either in some situations.

Greg

[EtLa]

They are certainly bright, but are kind of in between a Tele and a Strat soundiwse, having more bass than both, and not being as bright as either in some situations.

Greg

another thing to take into account is the air gap, if I remember correctly, the toaster pickup are not wound directly on magnet.

[David Schwab]

It typically uses about 7.5k of 44 gauge formvar also. They are certainly bright, but are kind of in between a Tele and a Strat soundiwse, having more bass than both, and not being as bright as either in some situations.

Don't forget that that's not a lot of wire wound on there. 44 AWG will get up to 7.5K pretty quickly.

I don't make any pickups using round poles, but I have found that using thicker blades sounds smoother than thinner blades. This could be the change in inductance, and also the increased sensing area of the string.

[Joe Gwinn]

I don't make any pickups using round poles, but I have found that using thicker blades sounds smoother than thinner blades. This could be the change in inductance, and also the increased sensing area of the string.

Eddy current loading varies as the square of the thickness of the laminations making up the blade, while inductance varies more-or-less directly as the total iron thickness of the blade (that is, the sum of the thicknesses of the laminations).

So, for example, consider a blade whose total iron thickness is 0.028", implemented in two ways. Design one is a single sheet of iron 0.028" thick, while design two is two sheets of iron each 0.014" thick with insulation between the sheets.

The inductance will be almost the same, but design two will have one fourth the eddy current load of case one. The "almost" is because eddy current loading does affect inductance, but this is a lesser effect than the total amount of iron and the total length of the magnetic paths through air and iron.

The difference between the two designs will likely be audible, and it's a matter of taste, intended market, and experiment to determine how many laminations of what thickness sounds best.

[rhh7]

I have wondered if it would be possible to take some poles intended for bass guitar, drill out the six holes in the strat cover, and wrap with 42 gauge? How would this work? Pardon me if this is too simple of a question.