charging magnets on 5-string P-bass pickups?

[Rodent]

for those who are making a split-coil P-bass type pickup for 5-string basses where both coils have 3 sets of magnets - how are you charging the coil that senses two string so that the 3rd set of slugs does not get magnetically charged?

note that this is NOT the configuration Fender utilizes with two different coil sizes



but a configuration like Nordstrand utilizes with identical bobbin outlines and where one pair of slugs is slightly recessed so as not to protrude thru the cover


(Regenerate bass with Nordstrand pickups)

the only way I can think to do this is to magnetize the coil prior to installing the 'placeholder' slug(s), install the dummy slug(s), and then wind the coil.


I'm curious if others have a better workflow that's not a two-part assembly type operation

all the best,

R

[David King]

Rod,
That's a great question. You can use two stacks of small diameter round neos and pile them up the front and back of each pole piece, magnetizing them individually. A tape head demagnetizer might also help kill off any residual charge in the dummies.

[David Schwab]

for those who are making a split-coil P-bass type pickup for 5-string basses where both coils have 3 sets of magnets - how are you charging the coil that senses two string so that the 3rd set of slugs does not get magnetically charged?

Why wouldn't you want all the magnets charged? It's a 5 string pickup. One side has three sets of magnets, and the other has two.

You need all the magnets charged or you won't pickup up those strings.

The only difference between the two pickup is one has two different size coils in different size covers, and the other has them in the same size covers.

Seeing the bottom they do seem to have 6 sets of magnets, so either they aren't charged or they are. Maybe they used steel rods or un charged magnets.

[Rodent]

as seen in your back side image, both coils contain three pairings of pole pieces. one of the coils has all three pairings magnetized and the other coil includes a pairing of non-magnetized dummy slugs with the coil installed towards the center of the body so that the uncharged slugs share the 'overlapped' string the two coils converge under, giving each string just one set of charged pole pieces to interact with

on all the 5-string P pickups I have purchased, there is always that one set of uncharged slugs. it's quite easy to verify the difference in magnetic pull with a piece of ferrous rod, screwdriver, etc ...


the more I think on this, the more I am convinced that in a production environment where more than just an occasional pickup set is made ... the slugs must be installed after the pole pieces are charged and before the coil is wound. this definitely increases the physical 'touch time' and increases the number of process steps for this pickup configuration. my interest here is to optimize the workflow to the most efficient means of producing this configuration, allowing me to train help to an already established best practice put in place and validated long before they become involved in fabricating the coils


I suspect that if all of the pole pieces were charged, the middle string (A on a typical BEADG 5-string tuning) would have phase issues since it would be equally sensed by both coils, hence the requirement for the pair of non-magnetized slugs

all the best,

R

[David Schwab]

Use non metallic rods for the extra poles.

If you look at the y they do their 5 string Jazz pickups, they have uneven size coils, as does the other 5 string P.

Uneven coils do pose a problem getting them to both sound the same though.

[Rodent]

non-magnetic poles is definitely something to consider, as my preference is to keep both coils the same physical size for several reasons

all the best,

R

[David King]

What about using un-oriented A5 for the dummy slugs? Alternatively you could just find some alloy with approximately the same permeability at the A5 in a soft magnetic material.
As I recall A5 is close to air for permeability so realistically a plastic slug at the end would probably accomplish about the same result.

[David Schwab]

As I recall A5 is close to air for permeability...

No, I think that's ceramic and neo magnets. Alnico has iron in it.

[David King]

I was thinking back to this very similar thread:
http://music-electronics-forum.com/t13580/#post107353
Mike's response further down:
http://music-electronics-forum.com/t13580/#post107582

[David Schwab]

I was thinking back to this very similar thread:
http://music-electronics-forum.com/t13580/#post107353
Mike's response further down:
http://music-electronics-forum.com/t13580/#post107582

I tried making one of these. It's very difficult to get the two sides to sound the same.

[Rodent]

a little time at McMaster gave way to finding these materials with a .188" nominal diameter.

8745K13
8571K42

there are many others available in this diameter, and I chose these simply for what appears to be a combination of good chemical resistance together with a low CoE. Pricing was under $1US/ft. If I go this route, I'd initially need to cut a small batch of these to length ... and if it looked like it was going to be a viable solution, I'd want to check into outsourcing a quantity

a question would be whether any of these materials are going to react with the insulation material of the wire over time. probably something that would be a good question for the company (Remington) I source my wire from, eh?

all the best,

R

[David Schwab]

a question would be whether any of these materials are going to react with the insulation material of the wire over time. probably something that would be a good question for the company (Remington) I source my wire from, eh?

Many bobbins are made from PVC, so no problem there. I've made bobbins from polycarbonate, so I wouldn't worry about hat either.

Don't you tape your magnets first? That's the thing you have to watch for.

[David King]

Why anyone uses pvc for anything beats me. Just go with acetal, it's 1/2 the price and will be so much easier to work with.
McMaster-Carr
You can stain the white to match any color you want. Personally I'd go with black. You should be able to find it locally for a whole lot less than McMaster.

[David Schwab]

Why anyone uses pvc for anything beats me. Just go with acetal, it's 1/2 the price and will be so much easier to work with.
McMaster-Carr
You can stain the white to match any color you want. Personally I'd go with black. You should be able to find it locally for a whole lot less than McMaster.

I was also thinking of acetal. But keep in mind that its hard to glue. I use it in molds for screw tunnels because epoxy wont stick to it.