Laminated Core

[Joe Gwinn]

If you want to know the change in the frequency response of a pickup from adding a laminated core, you must include the effect of the coil inductance because it is an important part of the circuit. I did not conclude that the effect the inductance would be negligible, as you said I did. All I did was consider a case where the effect of the laminations on the inductance would be small, just for simplicity. Read my statement (that you quoted) again. I do not think that there is any point in commenting on the rest of what you wrote until this misunderstanding is cleared up.

The tone of voice seems to be getting sharper, so maybe it's best to give this a rest.

[David Schwab]

Some Asian-made guitars, such as some Univoxes, would use humbuckers where one or both coils looked like a sort of "staple" coil from the top, but was two soft iron (?) slugs butted up against each other, looking like a pair of "combs", such as you'd see along the outside of a Jaguar pickup. Of course, there would be a ceramic magnet linking those slugs and another that might have adjustable screws in it.

Would you consider this a "laminated" core or does lamination have to involve more than two blade-like pieces?

Those were the Maxon pickups. They did that because they were stamping out the parts, not because they anted them laminated. Same thing with the "keeper" in the Hagstrom Bi-Sonic/Dark Star pickup. It's just easier to make that way since they could stamp out a thinner piece of steel and stack them up.

Since the pieces went insulated from one another they weren't really laminated.

[David Schwab]

That's basically what Bartolini does.

They also used to have the laminated core humbucker, which was a guitar pickup with exposed coils and laminated blades. The ones I had heard back in the 80s were wound pretty hot and had an enhanced midrange tone.

I used laminated cores in one of my bass pickups. Compared to a solid core (used with the same bobbin/windings/magnet) they had a brighter, edgier tone.

[David Schwab]

If you want no eddy currents, but need a sufficiently high permeability material to carry the permanent field to the strings, use ferrite.

EMG is doing that on some of their guitar pickups:



One reason to use, or not use ferrite poles is steel loads the pickup differently from ferrite. Depends on the tone you are looking for.

[big_teee]

Those EMGs look Sharp!
Black Chrome Maybe?

[David Schwab]

Those EMGs look Sharp!
Black Chrome Maybe?

Yeah, they call the finish "Diamond-like carbon (DLC)" and they also list them as "black nickel."

It's the James Hetfield signature set:

EMG Pickups / JH "HET" Set / Active / Signature Sets / Guitar / Electric Guitar Pickups, Bass Guitar Pickups, Acoustic Guitar Pickups

[Jason Rodgers]

Hi, folks. First post...

I built my first set of pickups recently: total uneducated and blind experiment using Home Depot 3/16" x 3/4" steel bar stock as the blade core, countertop laminate for flatwork, and neos. They work, but I came to understand later (thanks to David King and Veronica Merryfield) that I invited massive amounts of eddies and have a rather dark and muddy set of pickups. Oh well, it was fun, and they were custom built for my first guitar (you can see it on the mimf here, if interested MIMF ? View topic - The first by Jason Rodgers MIMF ? View topic - Experimental rail pickup construction: wiring question MIMF ? View topic - Jason's Pickup Winder).

Anyhoo, I like the blade/rail design for its simplicity and want to try again with a laminated core. Here's my question: how do you ground these laminates? If the strips are sealed or spaced to be insulated from one another, grounding brings them back together. I don't understand the technical discussion of Mr Sulzer and Mr Gwinn on the physics of laminated cores and their magnetic/electrical interaction. Is it important that the cores are separate in their physical orientation, but can be joined for grounding over a small junction; or is there some other way to go about this?

Thanks!

[Joe Gwinn]

Is it important that the cores are separate in their physical orientation, but can be joined for grounding over a small junction; or is there some other way to go about this?

You are correct that a single-point ground connection is what's needed. This forces the eddy currents to stay in each lamination, rather than being able to span multiple laminations.

[Jason Rodgers]

Ok, that makes sense. Thanks for the answer!

Now, how are folks going about making that ground connection? Is it something as simple as scraping a little of the insulating coating off a corner and bridging the lams with some conductive adhesive foil tape for a ground wire? Or is there some other contact made with base plates?

[David King]

Jason,

I suspect that drilling a small hole and inserting a copper rivet through would be sufficient. You could easily solder a drain wire to the copper. A short length of AWG 10 could be peened on each end.

[Jason Rodgers]

That's basically what I did with my pickups, so that's doable. Thanks, David.

I'm excited to try rail/blade-style pickups again with the laminated cores. Winding is fun!