Magnets & Copper Wire: A Pickup Building Thread

[Freekmagnet]

I meant a T head on the tops of the pole plates that you have. To widen out the field around the string, and make it less sensitive to string height.

Well, that would be helpful for a number of reasons - one of which would be string spacing. The pickup has to be adjusted just right for the poles to fit directly beneath the strings.

I think the easiest way would be to cut some steel strips and stick them on there.

 

[Bruce Johnson]

Well, that would be helpful for a number of reasons - one of which would be string spacing. The pickup has to be adjusted just right for the poles to fit directly beneath the strings.

I think the easiest way would be to cut some steel strips and stick them on there.

Yeah, that would be a good quick test. Some 1/4" x 1/8" steel strip, lying down, glued on. For production, you may be able to find some small iron T-beam or I beam stock. Or, mill some from rectangular stock. Let me know if you need some help with that.

 

[Jon Clegg]

Crude visualization of your field structure, Red is South, Blue is North:

Not to scale of course but I think this is what's causing some of the weirdness.

 

[Freekmagnet]

Crude visualization of your field structure, Red is South, Blue is North:

View attachment 3570808

Not to scale of course but I think this is what's causing some of the weirdness.

Wow! That’s some drawing! Thanks for posting.

Yeah, I can’t say weather or not that weird field is the cause of my woes. I definitely won’t dispute your theory. However, I’m going to experiment with smaller magnets and adjusting the shape and size of the poles before I add more poles.

Overall, the pickup sounds good - I just have to make some adjustments. Adding poles might alleviate the finicky nature if the pickup, but at the same time that would constitute a fairly sizable re-design. Note that I’m not entirely ruling out that possibility - I just want to begin by trying the easier avenues before I go nuclear!

 

[delta7fred]

I don't know if you are aware that the MM SR5 pickup magnets on the B string (and G but that's a whole other can of worms for another thread) are 20% weaker than the rest.

My guess is to alleviate the problem you are experiencing.

(As measured with a Gauss meter on my 2003 SR5.)

 

[Freekmagnet]

I don't know if you are aware that the MM SR5 pickup magnets on the B string (and G but that's a whole other can of worms for another thread) are 20% weaker than the rest.

My guess is to alleviate the problem you are experiencing.

(As measured with a Gauss meter on my 2003 SR5.)

Yeah, I’ve thought about that, too. I’m going to order some smaller magnets and see what happens with that. Maybe put the smaller (weaker) on the E string only.

 

[Freekmagnet]

I’m just doing my weekly update. I got some work done this week. I wound a new set of coils, tinkered around with the pole height, experimented with shielding my coils and built a rough little PCB. Here it is in the bass:

I knocked out that PCB in about 40 minutes. I used a Sharpie as a mask - I’ve never done that before, and it seemed to work. This stage I’d consider “extreme” prototyping ‘cuz sometimes you just gotta go in there and get it done by any means necessary. In a perfect world, I’d be knocking the PCB out with a miniature consumer-grade benchtop CNC router. I really hate dealing with etchant solution.

I lowered the poles on the E and the G string. The “wolf tone” I was getting seems to have been mostly abated. But I’m not sure - I keep thinking I hear it a little bit. Part of it might be the really old strings or my imagination.

I might have shortened the poles too much. The A and D strings are noticeably louder. The G is too quiet. That’s an easy fix. I’ll make new E and G poles and pop them in there over the weekend.

Overall, I’m feeling really good about this pickup. It sounds great. I just have a few adjustments to make, and I’m done. With this particular pickup, I think I’m hearing the “neodymium sound” and it’s interesting. It’s got this largeness and an immediacy without being overly aggressive. I think I like it.

On a side note, we’ve been having some really hot, dry weather in SoCal. There’s been a lot of fires. Anyway I looked at my unfinished holly-bound bass body and noticed this:

Another easy fix, boy am I glad this happened before I finished the bass!

 

[Freekmagnet]

I'm going to be gearing up this week for a "completed" prototype...

 

[Bruce Johnson]

I'm going to be gearing up this week for a "completed" prototype...

This is some amazing work, Jeremy! I hope you realize that there are only a few people in the world who are digging as deeply into pickup R & D as you are. Really. Rick Turner and Seymour Duncan would be proud to see this.

 

[Beej]

Very cool. I feel so child-like suggesting this, but have you ever tried to examine the magnetic field with paper and iron filings, or magnetic plotting compasses like so many of us did in science class back in the day? I can't help but wonder if laying some paper and iron filings over that pickup and observing the magnetic field might be informative... Or laying out 20 little plotting compasses around it when laying it on it's side or upside down...

 

[Freekmagnet]

This is some amazing work, Jeremy! I hope you realize that there are only a few people in the world who are digging as deeply into pickup R & D as you are. Really. Rick Turner and Seymour Duncan would be proud to see this.

“Amazing”? Wow, gosh thanks Bruce - I wouldn’t go that far! Rick Turner and Seymour Duncan actually know what they’re doing! I’m just a guy geeking out in my garage and throwing stuff at the wall in hopes that it sticks.

Very cool. I feel so child-like suggesting this, but have you ever tried to examine the magnetic field with paper and iron filings, or magnetic plotting compasses like so many of us did in science class back in the day? I can't help but wonder if laying some paper and iron filings over that pickup and observing the magnetic field might be informative... Or laying out 20 little plotting compasses around it when laying it on it's side or upside down...

That is a fun experiment, and I’ve actually researched it - but it’s a little more complicated than that. In order for it to work, you gotta build this clear container and use it to suspend the metal shavings in some kind of oil.

I was looking into doing computer simulations as well. There’s some free engineering software out there, but it’s way over my head. You have to enter a lot of data that frankly, I don’t understand. You need a lot of measurements I don’t have the equipment to make and a little trigonometry - which I never learned. I suppose at this stage of my life learning trig would be helpful.

There’s a cool website Link Removed with some basic simulations.

Bruce has some little credit-card sized thing-a-ma-bob at his shop he said he bought on Amazon. I don’t remember if he said that he found it very useful or not.

 

[NKBassman]

I’m just a guy geeking out in my garage and throwing stuff at the wall in hopes that it sticks.

Isn't that how Apple got started?

 

[Bruce Johnson]

I've been thinking about that too. What's a good way to get a picture of the magnetic field? The little card thing from Amazon was pretty useless.

I'm thinking: Find a small clear plastic box, maybe 4" x 2" x 2" deep. Pour it full of mineral oil, then stir in some iron filings. Hold the pickup face down, with the surface only slightly immersed in the oil. Photograph the pattern of the filings from the side, through the clear box.

Or maybe hold the pickup against the outside of the box, against the side?

 

[Jon Clegg]

I think laying the pickup on its sided and setting the box on top would give a pretty good picture. Yes, you would just be getting the side-lobes but those would be strongly influenced by the main structure. I think that laying the box in front of the pole pieces would give you an idea of what the field looks like.

 

[Freekmagnet]

Seymour Duncan would be proud to see this.

Years ago, I applied for a job at Seymour Duncan. They had a graphic design position open in their advertising department. I actually wanted the job, ‘cuz they have a pretty good in-house marketing machine. When I interviewed, they seemed really intrigued by the idea of an ad guy who understood and had actually used their products in the field. It was a two and a half hour interview! In the end, I guess they didn’t think I was a fit. They changed the job description on the posting the next day!

 

[SteveCS]

Years ago, I applied for a job at Seymour Duncan. They had a graphic design position open in their advertising department. I actually wanted the job, ‘cuz they have a pretty good in-house marketing machine. When I interviewed, they seemed really intrigued by the idea of an ad guy who understood and had actually used their products in the field. It was a two and a half hour interview! In the end, I guess they didn’t think I was a fit. They changed the job description on the posting the next day!

A marketeer who knows the product and can see through the flim-flam? No chance'!

 

[Bruce Johnson]

Years ago, I applied for a job at Seymour Duncan. They had a graphic design position open in their advertising department. I actually wanted the job, ‘cuz they have a pretty good in-house marketing machine. When I interviewed, they seemed really intrigued by the idea of an ad guy who understood and had actually used their products in the field. It was a two and a half hour interview! In the end, I guess they didn’t think I was a fit. They changed the job description on the posting the next day!

The problem was that they didn't want a marketing guy who could come up with wilder creative ideas than their R & D guys.

 

[Freekmagnet]

A marketeer who knows the product and can see through the flim-flam? No chance'!

The problem was that they didn't want a marketing guy who could come up with wilder creative ideas than their R & D guys.

haha yeah, marketing guys get kind of a bum rap. The problem is, marketing is a really broad field and there’s a lot of really bad marketing guys out there. And naturally, the only marketing anyone remembers is bad marketing.

I got the gist that the gal who interviewed me was looking for a regular old designer with shiny shoes and those fancy pieces of eyewear you always see in the cartoons.

And, I’m not a marketing guy - I’m in advertising - there’s some overlap, but there’s a big difference between the two!

 

[Freekmagnet]

I've been thinking about that too. What's a good way to get a picture of the magnetic field? The little card thing from Amazon was pretty useless.

I'm thinking: Find a small clear plastic box, maybe 4" x 2" x 2" deep. Pour it full of mineral oil, then stir in some iron filings. Hold the pickup face down, with the surface only slightly immersed in the oil. Photograph the pattern of the filings from the side, through the clear box.

Or maybe hold the pickup against the outside of the box, against the side?

That may be the box I read about on the pickup forum - maybe you were the one who posted it!

 

[slowburnaz]

So, @Bruce Johnson pointed me to this thread. I had posted about one of my multi-coil experiments over in the Pickups & Electronics forum, but this here is probably more appropriate.

Bruce, Freek, MPU... you guys do some really cool stuff! Inspiring!


Anyways, here's my latest set of multi-coils:

The technical stuff:
Each coil is made from roughly 10,000 turns of 42AWG. Magnets are .25" diameter X .78", alnico 5. String pairs are wired in series, RWRP, like mini P-bass sets. All string pairs are then wired in parallel with each other. Modern "Wal" configuration, only with theirs, each string pair is output into it own preamp buffer, as I understand it.

Coil bobbins are just some round transformer bobbins that I bought online.

The baseplates are PCBs, which I designed on easyeda.com, who can also fabricate your designs for you. Awesome service, really.

I drew up the covers in Fusion 360, and then had them 3D printed (SLA process) in black resin at a local shop.


These things sound really hi-fi to my ears. More than I expected. But, even with all the highs, the lows are there in spades, too. Maybe this is actually due to a pretty flat frequency response... I'm guessing that pairing these with a filter-based preamp would work well, since you could play with the resonant peak.

Anyways, here are some sound clips of these in my test bass. I've posted these in the other post, too, but I figure if the mods decide that other one isn't appropriate for the forum, at least it'll still be here. Direct from bass to Audacity, via Lightsnake cable (bass has an Audere 4-band preamp, all bands set flat):

Both pickups:
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Neck pickup solo:
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Bridge pickup solo:
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I think the next step is to play around with adding some small steel plates under each "row" of magnets.. see how that affects the tone as well.