Destroyed Fishman Rare Earth Blender

[verhoevenc]

So I got the distinct pleasure of taking apart a broken fishman rare earth blender pickup today and thought you guys might be as interested as I to see what was inside.


Two tiny bobbins for humbucking action, however I was surprised to see that in now way, shape, or form, did the magnets extend down through the coils. As you can see the center of the bobbins are just a thin little area. The little buttons of rare earth magnet just kinda sit on top in a recess.
Chris

[Mike Sulzer]

Neodymium has just about the same permeability as air, and so it would not raise the inductance of the coil much even if it did extend down through the coils. There is no point in making the magnets too strong, either. Steel cores (with neo on top) would give higher inductance and output, but a lower resonant frequency. You get a better acoustic sound with the higher resonant frequency, if that is what you want.

[FunkyKikuchiyo]

I'm trying to figure out the "stagger" of the magnets. It doesn't seem to follow any pattern I recognize, and there seems to be one missing. I could see having the B really low, but taking it out entirely seems excessive. Which side is the bass side and which is the treble side? Did any of that get modified when you took it apart?

[David Schwab]

I'm trying to figure out the "stagger" of the magnets.

It's for an acoustic guitar. They often have the B string lower or even missing.

[copperheadroads]

I get a few inquires about acoustic pickups ,But i never built one
After seeing that pic I want to build a strat pickup with neo magnets....omg
Thanks for posting

[verhoevenc]

The bass side is exactly where you think it is. That's the B that's missing. As for the high e looking black (not mentioned yet), although you can't see a magnet cause the hole is filled with black epoxy, I believe there is one in there mainly because they made a hole there while they just didn't bother for the b.
That said David, what is the rational with completely dropping the b?
Copper, can't wait to see/hear it!
Chris

[FunkyKikuchiyo]

I figured it must be the B that is dropped - it is always really loud on acoustic pickups, especially piezos. The part that confuses me is if you look at the E,A,D and G. Why would the D and G be lower than the E and A?

[fieldwrangler]

Neodymium has just about the same permeability as air, and so it would not raise the inductance of the coil much even if it did extend down through the coils. There is no point in making the magnets too strong, either. Steel cores (with neo on top) would give higher inductance and output, but a lower resonant frequency. You get a better acoustic sound with the higher resonant frequency, if that is what you want.

Well.. at least the field probably stays clear of the lower coil, which is usually a desirable thing with these designs.

However, don't you think it would be advantageous to draw the field lines through the primary sensing coil in some way?

'Course, with an active design there's a heckuva lot one can do with the preamp...

Bob Palmieri

[David Schwab]

Well.. at least the field probably stays clear of the lower coil, which is usually a desirable thing with these designs.

However, don't you think it would be advantageous to draw the field lines through the primary sensing coil in some way?

'Course, with an active design there's a heckuva lot one can do with the preamp...

Bob Palmieri

Bill Lawrence used to make an acoustic pickup with air coils, i.e., with no cores. As Mike said, that keeps it sounding more acoustic and less electric.

[Mike Sulzer]

Well.. at least the field probably stays clear of the lower coil, which is usually a desirable thing with these designs.

However, don't you think it would be advantageous to draw the field lines through the primary sensing coil in some way?

It does not matter if the permanent field intersects a coil or not. What matters is that the changing field from the vibrating string pass through the top coil with significantly higher intensity than the lower coil. Magnets, if they have significant permeability, can help amplify this field. But neo does not; its permeability is just slightly greater than air. So if you took all the magets out of this pickup and somehow stuck them above the strings, it would continue to work about the same.

'Course, with an active design there's a heckuva lot one can do with the preamp...

Bob Palmieri

Not much in terms of string balance. The primary purpose of the preamp here is to bring the level back up to what is expected and drive a line of any reasonable length. The pickup probably does not have quite the expected signal level.

[StarryNight]

what gauge was the coil wire? was it the same gauge on the top as on the bottom coil? how were the two coils wired together?
great post!

[Achiles]

Have a look:Expression System | Taylor Guitars
Itīs two tiny coils maybe 3 ohms.

[David Schwab]

Have a look:Expression System | Taylor Guitars
Itīs two tiny coils maybe 3 ohms.

That's a totally different pickup from the Fishman.

[Achiles]

Totally different ?
Both are humbucker,"missing pole pieces",rare earth,active.

[David Schwab]

Totally different ?
Both are humbucker,"missing pole pieces",rare earth,active.

Do you see two stacked coils on the Taylor pickup? I don't.



The Taylor pickup is part of a system of other transducers as well.

The Fishman pickup has the dummy coil under the string sensing coil, and the magnets on the top. The Taylor seems to have the magnets on the bottom and only one coil.