Magnets & Copper Wire: A Pickup Building Thread

[Northwood]

Man you've got some serious discusion here. Excellent.
@ Bruce Johnson. Maybe I missed it but I dont see the advantage of your bobbins. Its time consuming and one thing caught my attention.
Your rods are embedded in the bobbin forcing the windings of the coil out from the rods. Leaving roughly a half of a millimeter of space between them.
Later on one of the reasons to do parallel windings rather than scatter is to keep more of the windings of a more compact coil in the hot area around the rods.
This seems contradictory to me. Please elaborate.

Why not use an acrylic top plate - or perhaps even glass - on the bobbin to let the coil shine?
That would look awsome in some designs.

 

[Bruce Johnson]

Northwood;

My style of cast half-bobbins are actually very fast to make, once the tooling is done. The total labor to make up a bobbin/magnet assembly, in batches, is only a few minutes each. That includes casting, reaming the holes, installing the terminals, and assembling onto the magnets. I like the cast parts because they support the magnets well, holding them into a solid assembly while I'm doing the winding and the rest of the assembly. Plus I'm able to incorporate the strong terminals right into them, in between the magnets.

The wall thickness of the bobbin over the magnets is smaller than it looks, about 0.040" (about 1 mm). That works for me. There may be some advantage in getting the wire in tighter against the magnets, but I don't know if it would be much. The main thing in increasing the clarity and definition is to pull in the outside of the coil; making the cross section of the coil tall and narrow, so all the turns are within the strongest zone of the magnetic field. Making the coil tall also helps keep it narrow. I use 3/4" high magnets, and my cast bobbins keep the top and bottom flanges thin. My coil, in cross section one side, is about 0.680" high x 0.125" wide, packed tightly.

 

[Northwood]

I see your point. In my opinion without the 'walls' you win 1 mm proximity of the outer winding just like that.
Im not trying to be disrespectful, but I have an idea.
For the rigidity of the structure, are the walls on the outside of the magnet necessary?
The plastic between the magnets are curved around them and should be enough to hold them securely. No need for the outer walls. And the wire would be wrapped flush to the plastic/magnet.
I dont know if I make myself clear.
In other words, grind the plastic walls flush to the magnets. The remaining bobbin structure will securely hold the magnets and you gain 1mm of proximity.
Will that work?

 

[Bruce Johnson]

I understand what you are saying and I appreciate the technical suggestion. But, if I were to trim away the walls of the inner bobbin, that would leave nothing but the flange and the lumps of plastic between the magnets. It would be a very fragile part to cast and machine and assemble. It could be done, but I don't think it's worth the extra trouble, in manufacturing time. By the overall geometry, I've already squeezed the whole coil into the most powerful area of the magnetic field. I don't think squeezing it in that little bit closer would make enough of a difference to justify the extra complexity of making the bobbins. It's a design tradeoff.

And I realize that there's always the Fender-style construction, where the bobbin is just two flat flanges that are stamped or laser cut, and pressed onto the ends of the magnets. That can put the coil wire right against the magnets. But there are a lot of mechanical problems with that construction. I used flat flange construction on the first couple of prototype pickups I wound when I was learning, and didn't like them. When I got into the design of my pickups for my basses, I chose to go with cast bobbins. I like these cast half bobbins. It's turned out to be a simple and reliable process.

 

[Northwood]

You are right, the suggested design will flex a lot more than yours. You have the hands on experience that I lack, and obviously put a lot of thinking into your design. I respect that

What kind of mechanical problems did you encounter using the flat flange bobbins?

 

[Roxbororob]

Nice to see you in Bassplayer Bruce Johnson!

 

[Freekmagnet]

I figured I’d try building a multi-coil pickup this week.

These have about 5000 turns of 43awg wire wrapped around 1/16” mild steel cores. I used some old scraps of mat board soaked in glue as bobbin material. I usually use paper and cardboard for prototyping coils ‘cuz it’s cheap and easy to cut.

I have some ceramic 8 bars and some neodymium magnets that fit between the blades. I’ll see which ones give me more kick. If the coils are too wimpy, I might be able to squeeze 6000 turns of 44awg.

We’ll see how it goes...

 

[NKBassman]

I figured I’d try building a multi-coil pickup this week.

View attachment 3345025

These have about 5000 turns of 43awg wire wrapped around 1/16” mild steel cores. I used some old scraps of mat board soaked in glue as bobbin material. I usually use paper and cardboard for prototyping coils ‘cuz it’s cheap and easy to cut.

I have some ceramic 8 bars and some neodymium magnets that fit between the blades. If the coils are too weak, I might be able to squeeze 6000 turns of 44awg.

We’ll see how it goes...

Cool! When you're testing, don't forget to try them in both series and parallel humbucking config.

 

[Bruce Johnson]

I figured I’d try building a multi-coil pickup this week.

View attachment 3345025

These have about 5000 turns of 43awg wire wrapped around 1/16” mild steel cores. I used some old scraps of mat board soaked in glue as bobbin material. I usually use paper and cardboard for prototyping coils ‘cuz it’s cheap and easy to cut.

I have some ceramic 8 bars and some neodymium magnets that fit between the blades. I’ll see which ones give me more kick. If the coils are too wimpy, I might be able to squeeze 6000 turns of 44awg.

We’ll see how it goes...

That looks like a very interesting combination, a cross between a linear multi-coil and a sidewinder. Maybe call it the MultiFreekWinder? The pickup in Ampeg's 1967 AMB-1 Scroll Bass was somewhat like this. A separate (round) coil for each string, with a A5 rod magnet in each, and a steel bar at the bottom connecting the magnets together. The rod magnets were alternating polarity, all mechanically pressed into the steel bar. So the magnetic structure was a comb, with the fingers alternating polarity. And, of course, the coils were connected in series, alternating directions. A full humbucker.

Is that what you are thinking of doing here, an alternating humbucker array?

You are getting into some serious pickup R & D here, Jeremy. Pushing the boundaries into unknown territory. Where the boutique winders fear to tread! Carry on! And watch out for those stray magnetic fields.

 

[Freekmagnet]

That looks like a very interesting combination, a cross between a linear multi-coil and a sidewinder. Maybe call it the MultiFreekWinder? The pickup in Ampeg's 1967 AMB-1 Scroll Bass was somewhat like this. A separate (round) coil for each string, with a A5 rod magnet in each, and a steel bar at the bottom connecting the magnets together. The rod magnets were alternating polarity, all mechanically pressed into the steel bar. So the magnetic structure was a comb, with the fingers alternating polarity. And, of course, the coils were connected in series, alternating directions. A full humbucker.

Is that what you are thinking of doing here, an alternating humbucker array?

You are getting into some serious pickup R & D here, Jeremy. Pushing the boundaries into unknown territory. Where the boutique winders fear to tread! Carry on! And watch out for those stray magnetic fields.

I’m not sure what I’m doing yet - I’m just trying to use up some of these magnets and wire I have laying around!

I’m just going to use a pair of coils to replace the single coils in a more “traditional” humbucker. I figured I could wire the two pairs in series and them in parallel or vice-versa. Or, I could wire them from top to bottom N-S | S-N and wire the opposing N-S coils in sort of a “comb” as you put it. Or is that an alternating humbucker array?

Basically, I’m just going to wind and see what I come up with. I want a “fatter” pickup than that “skinny” sidewinder I’ve been building.

 

[Freekmagnet]

A little update:

I broke the starting lead on one of the coils. I couldn’t fix it, so I had to rewind it. The potting solution won’t be near dry until tomorrow.

That left me with one set of coils. That turned out to be OK, because I was able to test it and see how it performed on its own.

I used 3 ceramic 8 magnets. One one each side of the blades and one in the middle. I tried the neodymium magnets, but for some reason, they’d short out the coils. I’ll have to figure out why that’s happening another time. I couldn’t pinpoint the cause.

Overall, the pickup sounded OK, but just OK. I had a little more output than I had anticipated. A surprising amount of bass, although it could have been a little tighter-sounding. I think that the pickup sounded a little dark with too emphasis on the upper mids. I’d expected it to be a little brighter - it is after all, a mini-humbucker. In past C8 humbucker builds, I’ve had trouble controlling the brightness. I guess I haven’t built a pickup with this magnetic structure before. What was good was that the pickup had a decent amount of warmth and did not have the harsh, unstable C8 vibe. I guess those steel poles really help.

I think what I’ll do is finish out the first quad-coil. Then, I think I’ll use 42awg and bring the wind count down to about 3750-4000 turns.

 

[Bruce Johnson]

I’m not sure what I’m doing yet - I’m just trying to use up some of these magnets and wire I have laying around!

I’m just going to use a pair of coils to replace the single coils in a more “traditional” humbucker. I figured I could wire the two pairs in series and them in parallel or vice-versa. Or, I could wire them from top to bottom N-S | S-N and wire the opposing N-S coils in sort of a “comb” as you put it. Or is that an alternating humbucker array?

Basically, I’m just going to wind and see what I come up with. I want a “fatter” pickup than that “skinny” sidewinder I’ve been building.

Ah, okay. When I saw the four skinny coils and you said Multi-Coil, I thought you were thinking of mounting them one for each string, with the bar in line with the string. That's what I meant by a Linear Multi-Coil, and why I referred to the Ampeg pickup. So, you're intending to mount the multiple skinny coils crosswise?

If you've worked out the technique for making long skinny coils, you should think about trying a linear multi-coil, with the sidewinder-style magnet frame.

 

[Freekmagnet]

Ah, okay. When I saw the four skinny coils and you said Multi-Coil, I thought you were thinking of mounting them one for each string, with the bar in line with the string. That's what I meant by a Linear Multi-Coil, and why I referred to the Ampeg pickup. So, you're intending to mount the multiple skinny coils crosswise?

If you've worked out the technique for making long skinny coils, you should think about trying a linear multi-coil, with the sidewinder-style magnet frame.

Wow, that'd be a really interesting pickup! It'd be tricky, but totally doable. I'd have to make some really tall and narrow coils. I have some .02" stainless steel I could laminate and make a .04" pole piece. Then I'd have to order some smaller neos. I think they have some .25" x .1875" magnets that would work The sidewinders are like, crazy bright. Wiring 4 of them in series would be interesting.

I'll try that after I finish this one. I think this one will be pretty straightforward. I can already see where it's going and either I'm going to like it or not.

However, I should point out that if I reduce the wind count and use #42 wire, I'll basically be making two mini T-40s. I drew up this little face plate that I could make out of nickel silver.

<pickup humor> I think I'll call it the T-1000 Super Duper Ferrite. </pickup humor>

 

[Freekmagnet]

OK, I made the second set of coils with 5000 turns of #43 wire. I hooked all the coils together and wired series + series in parallel. I didn't really like the sound of the first set of coils and all four together sounded worse! I kind of knew that this would be the case; in the past, I've wound a few humbuckers with ceramic magnets, and once they get up past a certain amount of turns, they start getting really flabby in the bass. I think the steel poles may have made them dark way faster as well.

I wound a new pair of coils with #42 wire. The idea was to take them down to 3750 turns, but on the second coil, I ran out of wire at 3600! I tried unspooling the first coil to match the second, but process was awkward and I kept losing count. I used my DCR to make them approximately the same.

Anyway, the first pair of coils sound pretty danged good! They have pretty decent output, too. When I hook the second pair up, they should sound great. I should have known that 5000 would have been too much, but oh well.

My next dilemma is this: do I order more #42 wire? I'm almost out of #43, but I have an almost a full spool of #44. I'm temped to just wind up a set of four coils with the the #44. It wouldn't hurt - I'd lose a little bass, gain a little mid-emphasis and they'd be a little brighter. But, I'd probably gain that bass back when I hook up the second pair of coils. I also might loose a little output. Worst comes to worst, I could try the #44, and if the pickup isn't loud enough, I can always buy another spool of #42 or #43.

I'm digging this too - I'm basically designing two pickups at once, maybe even three depending on how you look at it.

 

[NKBassman]

OK, I made the second set of coils with 5000 turns of #43 wire. I hooked all the coils together and wired parallel + parallel in series. I didn't really like the sound of the first set of coils and all four together sounded worse! I kind of knew that this would be the case; in the past, I've wound a few humbuckers with ceramic magnets, and once they get up past a certain amount of turns, they start getting really flabby in the bass. I think the steel poles may have made them dark way faster as well.

I wound a new pair of coils with #42 wire. The idea was to take them down to 3750 turns, but on the second coil, I ran out of wire at 3600! I tried unspooling the first coil to match the second, but process was awkward and I kept losing count. I used my DCR to make them approximately the same.

Anyway, the first pair of coils sound pretty danged good! They have pretty decent output, too. When I hook the second pair up, they should sound great. I should have known that 5000 would have been too much, but oh well.

My next dilemma is this: do I order more #42 wire? I'm almost out of #43, but I have an almost a full spool of #44. I'm temped to just wind up a set of four coils with the the #44. It wouldn't hurt - I'd lose a little bass, gain a little mid-emphasis and they'd be a little brighter. But, I'd probably gain that bass back when I hook up the second pair of coils. I also might loose a little output. Worst comes to worst, I could try the #44, and if the pickup isn't loud enough, I can always buy another spool of #42 or #43.

I'm digging this too - I'm basically designing two pickups at once, maybe even three depending on how you look at it.

Wiring them up in series/series should punch up the low end if its lacking.

 

[Freekmagnet]

Wiring them up in series/series should punch up the low end if its lacking.

True. I’m getting decent low end now and I’m augmenting it with an MM preamp. (Still looking for that magic bridge pickup)

All of those coils in series would be monstrous!

 

[Bruce Johnson]

I'd try winding them with 3600 turns of #44, and then putting them all in series. If that's getting you in the right range, keep working with the #44 (since you have plenty), adjusting the number of turns up and down.

In my experience with weird pickups, I've found that the first parameter set you should work out is the number of turns in relation to the magnet structure and the coil geometry. That seems to be the most important thing. For a particular strength and shape of the magnetic field, and a coil geometry, there's an optimal number of turns which will bring the level of the signal into the right range to work well with the amp. That's where you need to do the initial experimentation. Figure out how many turns that combination likes best.

Changing the wire gauge (while keeping the turns the same) will change the resistance, which will shape the EQ curve somewhat. Larger gauge/lower resistance makes the curve flatter; smaller gauge/higher resistance puts a lump in the EQ curve.

So again, the ideal order of the R & D is:

1. Decide on the magnet structure; geometry, choice of magnets, etc.
2. Decide on a bobbin geometry to mechanically fit the magnet structure.
3. Experiment to find the optimal number of turns for that combination. Preferably using a larger gauge wire to keep the EQ curve fairly flat, and to establish the maximum physical size the coil will need to be, and that it will fit in the bobbin. Find the number of turns that gives you the best working signal strength, overall frequency range, and clarity (if you want it). Lock down the number of turns.
4. Play with the wire gauge to fine tune the EQ curve.

 

[Freekmagnet]

I'd try winding them with 3600 turns of #44, and then putting them all in series. If that's getting you in the right range, keep working with the #44 (since you have plenty), adjusting the number of turns up and down.

In my experience with weird pickups, I've found that the first parameter set you should work out is the number of turns in relation to the magnet structure and the coil geometry. That seems to be the most important thing. For a particular strength and shape of the magnetic field, and a coil geometry, there's an optimal number of turns which will bring the level of the signal into the right range to work well with the amp. That's where you need to do the initial experimentation. Figure out how many turns that combination likes best.

Changing the wire gauge (while keeping the turns the same) will change the resistance, which will shape the EQ curve somewhat. Larger gauge/lower resistance makes the curve flatter; smaller gauge/higher resistance puts a lump in the EQ curve.

So again, the ideal order of the R & D is:

1. Decide on the magnet structure; geometry, choice of magnets, etc.
2. Decide on a bobbin geometry to mechanically fit the magnet structure.
3. Experiment to find the optimal number of turns for that combination. Preferably using a larger gauge wire to keep the EQ curve fairly flat, and to establish the maximum physical size the coil will need to be, and that it will fit in the bobbin. Find the number of turns that gives you the best working signal strength, overall frequency range, and clarity (if you want it). Lock down the number of turns.
4. Play with the wire gauge to fine tune the EQ curve.

Bruce, that’s great suggestion and I think you did a great job of laying out succinct illustration of a pickup R&D roadmap.

I will probably wind up a set of #44 coils largely because I’m curious what the difference in sound will be. It would be good to comfim my findings on how the change in wire gauge will affect the sound of the pickup. And, as you pointed out, it would be good to test and hear how the whole package works in unison and fine tune it by changing the wire gauge.

Right now, the one set of coils on their own sound about right to me. If anything, I could maybe use a little more clarity, but where it’s at now is by no means a deal-killer. I could see maybe taking them down by 300-400 turns.

But then, this brings up another factor altogether: I’m testing these pickups in crummy Made in China Squier tester bass. When I was working on my last pickup design and I finally moved one over to my completed Modelo Uno bass, the difference in clarity was like night and day! So maybe 3600 turns is perfect! I guess I won’t know until I drop the finished pickup into an actual guitar.

 

[Freekmagnet]

Any of you guys out there have any advice on tensioning devices? I’ve just been using little pieces felt pressed in a c-clamp. It’d be nice to have a more consistent tensioning device. I was thinking about rigging up some screen door parts.

 

[rudy4444]

Any of you guys out there have any advice on tensioning devices? I’ve just been using little pieces felt pressed in a c-clamp. It’d be nice to have a more consistent tensioning device. I was thinking about rigging up some screen door parts.

I use two wooden discs compressed by a small spring with felt on their inner faces. The tension is adjustable and it's very easy to pull up the top disc if I want to remove the wire. This setup gives me a very consistant winding tension and all I have to do is guide the wire on the bobbin.