Lowest magnetic pull with a reasonably efficient pickup

[JD0x0]

I'm looking to DIY an electric guitar pickup with the lowest amount of magnetic pull possible while still providing a reasonable output. For those of you with more experience and knowledge, what sort of set up would provide the lowest amount of magnetic pull on the strings for a given distance from the strings? Bar Mag or rods type? Dual Blade, Single blade, Single blade (stacked), Stacked rods, Lace 'sensor' set-up, etc.
Seems I would want a narrow magnetic window, and a low gauss magnet. Compensate output by using a relatively high turn count and using care to avoid internal shorts and excessive eddy losses

[LtKojak]

I would want a narrow magnetic window, and a low gauss magnet. Compensate output by using a relatively high turn count and using care to avoid internal shorts and excessive eddy losses

Why?

What exactly are you trying to accomplish by doing that?

[rjb]

I'm looking to DIY an electric guitar pickup with the lowest amount of magnetic pull possible while still providing a reasonable output....
what sort of set up would provide the lowest amount of magnetic pull on the strings for a given distance from the strings?

Piezo.

[copperheadroads]

Piezo.

Good answer.....Was going to reply a couple of times but it was hurting my brain with all the demands ....

[David King]

Isn't an HB about as efficient a pickup as one could buy off the shelf?
If I were designing from scratch I'd do what Bartolini does, a laminated steel inverted comb with a small coil for each string (alternating wind directions for hum cancelling) around each tooth of the comb. Then one or two bar magnets on either side of the backbone.

[eschertron]

Wasn't there a thread on here a few months/years ago where directly magnetizing the strings was mentioned as a way to eliminate pickup magnets? So the pickup would have just a coil to intercept the flux from the strings? Kind of a sideways way of doing what the OP asked...

[bbsailor]

As an alternative to placing a magnet below each string, think about this. Use seven .125" diameter magnets spaced about .125" to .275" apart with the string located in the middle of the adjacent magnets. You will need to adjust the spacing to have the strings align properly. This way there is a magnet on both sides of each string including the end strings where this is typically lacking. There will be less downward pull as the string sits in the gap between magnets but gets the benefit of a magnet on each side of the string. Also, the use of .125" diameter magnets allows you a little more bobbin room, when using the conventional pickup footprint, for wire to make the pickup a little more sensitive.

This is just a different approach to minimizing magnet pull.

Joseph J. Rogowski

[rjb]

I'm guessing that the reason for specifying "lowest amount of magnetic pull possible" is to maximize sustain.

In this thread http://music-electronics-forum.com/t38127/, the smart guys explained that to minimize the magnetic pull on the strings, you minimize the change in the magnetic field through which the strings travel. In other words, you want those imaginary field lines near the strings to be parallel and perpendicular to the string travel. (Of course, the smart guys said it in a much more eloquent and technically-correct fashion.)

Note that this does not mean you need to use a weak magnet; Mike S. suggested experimenting with an air coil and a very strong magnet positioned far from the strings.

The most (semi-)practical configuration that meets the criterion may be the Supro/Valco/Coodercaster string-through pickup mentioned in the thread.
Here's Jason Lollar's take on it: String-Through Steel Guitar Pickup

Here's a quick and dirty alternative: take a a dual blade pickup and try mounting a steel guard over the strings.
I think this would reduce magnetic pull- although not to the lowest possible level- by "bending" the field upward.

But being pedantic about it, I assert that the "lowest amount of magnetic pull possible" is zero.
If piezos don't fit the bill, maybe something like this might be fun to try: Lightwave Systems | The Technology behind Willcox Guitars Optical Pickup Technology

[Mike Sulzer]

Another way is to use steel cores, rod or blade, and try various Neo magnets, from tiny to larger, until you get what you want.

I'm looking to DIY an electric guitar pickup with the lowest amount of magnetic pull possible while still providing a reasonable output. For those of you with more experience and knowledge, what sort of set up would provide the lowest amount of magnetic pull on the strings for a given distance from the strings? Bar Mag or rods type? Dual Blade, Single blade, Single blade (stacked), Stacked rods, Lace 'sensor' set-up, etc.
Seems I would want a narrow magnetic window, and a low gauss magnet. Compensate output by using a relatively high turn count and using care to avoid internal shorts and excessive eddy losses

[dawin12]

I think that because most of the guys here are pickup-makers, they kind of answered your question in an indirect, exotic, navel-gazing fashion. I'm not a pickup-maker, so I'll try to address your concerns in a boring, more conventional way.

What came to mind for me when reading your question was Stratitis. You can Google it, but my understanding is that it's an undesirable tone that results when a Strat pickup is a little too close to the strings - too much magnetic pull. Because I haven't heard of an exaggerated "itis" associated with other pickups, I'd say that a Strat design has certain aspects you should avoid. Specifically, no rod magnets(no narrow magnetic window), no single-coil, and no stronger magnetic field NEAR the strings.

For your desired output, humbucker would be my recommendation because versus a comparably hot single-coil, the HB's magnetic field would be less intense since it's essentially shared between the two halves.

I like rjb's post on horseshoe designs. It brings up the issue of a uniform magnetic field - one without sudden changes. I'm guessing a fat blade would throw a more uniform field than cylindrical pole pieces, but I'd defer to others on that. This could possibly help you decide which direction to go in: Magnetic fields in pickups. I find the visuals a little hard to interpret, but two comparisons are VERY interesting for this application: S-45 versus S-90 and HB w/A5 versus HB w/A2. Clearly, the S-45/90 comparo shows that a ferrous plate under a pickup can smooth out the field. Does anyone know if this works equally well on a humbucker? A little less obvious is that HB w/A2 helps out in this regard too. Do you guys think he should also experiment with degaussed or not fully-charged A2 bars? What about taller bobbins?

That's just my ignorant $.02. Good luck!

[Fluoroscope 5000]

Considering that Steel can easily be saturated by Nd magnets, I’d think you'd need very small Nd magnets indeed. Maybe 2~4mm thick depending on the type? C5 or C8 might just be easier, and make sure to ground the poles/core directly to the chassis. Efficiency is hard to manage without knowing exactly how everything interacts and how the field is configured, but increasing inductance with Steel is more efficient than with more winds. You want all the winds to be as close to the core and strings as possible. A small, square cross-section coil close the core and strings will be the most efficient. Hand-winding invariably produces excess internal distributed C and possibly eddy-current shorts. I think 43AWG poly wound very slowly is the best bet, doing whatever you can to make the cross-section square, so all the wire is closer to the strings and core combined. For good articulation above 4kHz, you should probably aim for 3.5~5H for 500k pots, or 2~3H for 250k pots. A higher H value will require a lower C cable to get a sweet articulate high end. The magnetic aperture can be fine-tuned via screw height. I see no reason not to use screws in each coil. A Steel base-plate would probably be counter productive in a standard HB design, drawing the field through the coils and what not. Use “German Silver”, or use Brass for a different quality. Bill Lawrence sated that a thin brass Tele base-plate warms the sound in some way. I really like the crisp warm sound of my bass-plate GFS bridge D180 in my semi-hollow, but I don't think they generally sound good in hard sounding solid body guitars. Certain types of 4xx series Stainless Steel as the core and screws can work for less bass emphasis and a more focused resonance peak. Not sure where you'd get the core material. Screw inserts or nuts?? FI, you might want that in the neck, and Steel in the bridge...or use mini-HB bobbins in the neck for less upper-harmonic roll off.

[Mike Sulzer]

Saturating the steel is not the problem; pickups use short open cores, and it is not possible to saturate the steel, not as with a magnetic circuit that forms a complete loop. You can easily produce fields with Neo and steel cores that completely destroy the natural vibration of the string, and that is why you use very small Neos when you want a weak field. Experimentation is necessary.
,

Considering that Steel can easily be saturated by Nd magnets, I’d think you'd need very small Nd magnets indeed. Maybe 2~4mm thick depending on the type? C5 or C8 might just be easier, and make sure to ground the poles/core directly to the chassis. Efficiency is hard to manage without knowing exactly how everything interacts and how the field is configured, but increasing inductance with Steel is more efficient than with more winds. You want all the winds to be as close to the core and strings as possible. A small, square cross-section coil close the core and strings will be the most efficient. Hand-winding invariably produces excess internal distributed C and possibly eddy-current shorts. I think 43AWG poly wound very slowly is the best bet, doing whatever you can to make the cross-section square, so all the wire is closer to the strings and core combined. For good articulation above 4kHz, you should probably aim for 3.5~5H for 500k pots, or 2~3H for 250k pots. A higher H value will require a lower C cable to get a sweet articulate high end. The magnetic aperture can be fine-tuned via screw height. I see no reason not to use screws in each coil. A Steel base-plate would probably be counter productive in a standard HB design, drawing the field through the coils and what not. Use “German Silver”, or use Brass for a different quality. Bill Lawrence sated that a thin brass Tele base-plate warms the sound in some way. I really like the crisp warm sound of my bass-plate GFS bridge D180 in my semi-hollow, but I don't think they generally sound good in hard sounding solid body guitars. Certain types of 4xx series Stainless Steel as the core and screws can work for less bass emphasis and a more focused resonance peak. Not sure where you'd get the core material. Screw inserts or nuts?? FI, you might want that in the neck, and Steel in the bridge...or use mini-HB bobbins in the neck for less upper-harmonic roll off.

[Fluoroscope 5000]

Oh. Thanks for chiming in on this Mike. Is it that a PAF style magnet circuit is in effect more of a "horseshoe" that the steel won't be saturated? This is valuable info.

[Mike Sulzer]

The PAF humbucker should not be viewed as a horseshoe magnet. The steel pole pieces are much higher permeability than the Alnico magnet, which then does not couple them effectively. And a good thing. If you really do couple them together with high permeability material, it picks up hum rather than rejecting it.

Oh. Thanks for chiming in on this Mike. Is it that a PAF style magnet circuit is in effect more of a "horseshoe" that the steel won't be saturated? This is valuable info.

[Mark Hammer]

You know, the degree of magnetic pull really only becomes an issue if the mass of the string is low enough, and the polepiece close enough, that the polepiece can damp string vibration.

Nobody really concerns themselves with magnetic pull when it comes to basses, or wound guitar strings for that matter.

Now, if you're Billy Gibbons, and using those ultra thin strings on a short scale guitar, magntic pull may well be an issue of concern for your unwounds.