Magnets & Copper Wire: A Pickup Building Thread

[Freekmagnet]

@slowburnaz -

Wow, that's some nice work you've done there! I love how you solution you came up with for the wire terminals!
I use easyeda as well. It's pretty cool for a free piece of software. What are their prices and turnaround like? I use OSHPark - the price is right but the turnaround is 2-3 weeks.

Thanks for posting!

 

[slowburnaz]

@slowburnaz -

Wow, that's some nice work you've done there! I love how you solution you came up with for the wire terminals!
I use easyeda as well. It's pretty cool for a free piece of software. What are their prices and turnaround like? I use OSHPark - the price is right but the turnaround is 2-3 weeks.

Thanks for posting!

Many thanks, sir!

My last order, for 10 PCBs in black, w/ lead-free solder masking, came out to $33.40, so just over 3 bucks each before shipping. And for the little red "risers", those were like $0.90 each. I used those, because the plan is to encase them in epoxy, and that raises the terminals up and out of the epoxy fill line... and it looks kinda cool, to me, though when in an instrument, you'd never see it. lol

Turnaround has always been fast! I ordered these on 10/4, and they were delivered on 10/10. That's pretty par for the course with them.

On the subject of epoxy... I've had some bad results using CPES to pot my coils. Not sure what I'm doing wrong, but every set of coils that I used CPES on shorted out. Hell, it even ate through the plastic cup I mixed it in, which I thought was pretty weird, so I'm assuming it ate through the wire insulation. :shrug:
In any case, I potted these in paraffin.

 

[Freekmagnet]

Many thanks, sir!

My last order, for 10 PCBs in black, w/ lead-free solder masking, came out to $33.40, so just over 3 bucks each before shipping. And for the little red "risers", those were like $0.90 each. I used those, because the plan is to encase them in epoxy, and that raises the terminals up and out of the epoxy fill line... and it looks kinda cool, to me, though when in an instrument, you'd never see it. lol

Turnaround has always been fast! I ordered these on 10/4, and they were delivered on 10/10. That's pretty par for the course with them.

On the subject of epoxy... I've had some bad results using CPES to pot my coils. Not sure what I'm doing wrong, but every set of coils that I used CPES on shorted out. Hell, it even ate through the plastic cup I mixed it in, which I thought was pretty weird, so I'm assuming it ate through the wire insulation. :shrug:
In any case, I potted these in paraffin.

That's a good price. OSHPark works out to be about the same, but the turnaround is slooooow. The nice thing is that I only have to order 3 - that really good if I'm just experimenting with a design. I'll check out easyeda next time and bite the bullet and order 10 pcbs.

I haven't had problems with my coils shorting out with the CPES. What brand of wire and CPES are you using? I use Remington wire with the solderable polyurethane insulation with Smith CPES. Lately, I've been doing mixing in a Dixie cup.

I don't see a problem with using paraffin, but it would just weird me out to think that the wax in the coils would be repelling the epoxy. I usually dab some wood glue around the wire solder joints - the epoxy can get really hot and might actually break the wire as it expands and contracts.

Your pickups look great. They sound good on the demo, too.

 

[slowburnaz]

That's a good price. OSHPark works out to be about the same, but the turnaround is slooooow. The nice thing is that I only have to order 3 - that really good if I'm just experimenting with a design. I'll check out easyeda next time and bite the bullet and order 10 pcbs.

I haven't had problems with my coils shorting out with the CPES. What brand of wire and CPES are you using? I use Remington wire with the solderable polyurethane insulation with Smith CPES. Lately, I've been doing mixing in a Dixie cup.

I don't see a problem with using paraffin, but it would just weird me out to think that the wax in the coils would be repelling the epoxy. I usually dab some wood glue around the wire solder joints - the epoxy can get really hot and might actually break the wire as it expands and contracts.

Your pickups look great. They sound good on the demo, too.

I'm using the Smith's stuff as well. I suppose it could have been the encapsulation process, but it's weird for them all to have shorted out. I'm also using West Systems epoxy for that, with the 206 slow hardener.

But, I'll be trying it again. I've got it, so why not? The wood glue on the solder joints isn't a bad idea. Maybe hot glue would work there, too.

 

[Bruce Johnson]

That's weird about your problems with CPES potting. I've been using it for about 15 years for all of my pickups, and I've never once had any problems with it shorting coils. What brand are you using? Are you sure you aren't mixing it too hot (too much activator)? When I use it, it never gets warm or hot at all.

 

[slowburnaz]

That's a good price. OSHPark works out to be about the same, but the turnaround is slooooow. The nice thing is that I only have to order 3 - that really good if I'm just experimenting with a design. I'll check out easyeda next time and bite the bullet and order 10 pcbs.

Through EasyEDA, you can order a minimum of 5, so not too bad. I've just noticed that the difference in price between 5 and 10 is pretty negligible, so I did the 10.

 

[slowburnaz]

That's weird about your problems with CPES potting. I've been using it for about 15 years for all of my pickups, and I've never once had any problems with it shorting coils. What brand are you using? Are you sure you aren't mixing it too hot (too much activator)? When I use it, it never gets warm or hot at all.

I thought it was weird, as well. I mean, it's the Smith's stuff, and I'm mixing it 1:1 like it says to do. Thought it strange that it was eating through my little plastic cups, too.

 

[Will_White]

Anybody have experience winders like this?

Manual Handheld WINDING Machine Coil Winder Electric Double Purpose Counting for sale online | eBay

 

[Freekmagnet]

I thought it was weird, as well. I mean, it's the Smith's stuff, and I'm mixing it 1:1 like it says to do. Thought it strange that it was eating through my little plastic cups, too.

Yeah that Smith's stuff is pretty potent. It's basically acetone with some epoxy mixed in. It will eat through styrene in a second. It doesn't seem to affect polyurethane at all. Once it hardens, the wires are a solid mass of plastic and copper.

What kind of insulation does your wire have on it? Like I said, I use the wire with the solderable polyurethane insulation and it holds up no prob.

 

[Freekmagnet]

Anybody have experience winders like this?

Manual Handheld WINDING Machine Coil Winder Electric Double Purpose Counting for sale online | eBay

I haven't tried one myself. Winding a pickup completely by hand would be a little tiring after about 100 turns!

 

[Will_White]

I haven't tried one myself. Winding a pickup completely by hand would be a little tiring after about 100 turns!

I'm planning on hooking it up to a drill, but I will have to do one by hand if I end up getting one just so I can say that I have.

 

[Beej]

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:
View attachment 3589853
View attachment 3589855

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.

Just wow. Thanks for sharing - they sound great to my ears, very hifi...

 

[slowburnaz]

Yeah that Smith's stuff is pretty potent. It's basically acetone with some epoxy mixed in. It will eat through styrene in a second. It doesn't seem to affect polyurethane at all. Once it hardens, the wires are a solid mass of plastic and copper.

What kind of insulation does your wire have on it? Like I said, I use the wire with the solderable polyurethane insulation and it holds up no prob.

I'm using Elektrisola P155 wire, so it's polyurethane. I'm thinking more and more that it was something to do with the encapsulation process. I had left some slack in the connections before the solder joint, thinking that might help with contractions and expansions, but maybe that just left more for the epoxy to grab onto and "tug" on while it was curing. If/when I try that again, I'll probably do like you've done and apply some wood glue or hot glue over the joints.

 

[Freekmagnet]

I'm using Elektrisola P155 wire, so it's polyurethane. I'm thinking more and more that it was something to do with the encapsulation process. I had left some slack in the connections before the solder joint, thinking that might help with contractions and expansions, but maybe that just left more for the epoxy to grab onto and "tug" on while it was curing. If/when I try that again, I'll probably do like you've done and apply some wood glue or hot glue over the joints.

Yeah, that could very likely be the cause. If the wires are even a little tight, they'll snap. I've had it happen before. I usually leave a little slack - enough to make a nice curve in the wire - and then dab some wood glue on the joint and any slack in the wire before I encapsulate the pickup.

 

[Freekmagnet]

I'm planning on hooking it up to a drill, but I will have to do one by hand if I end up getting one just so I can say that I have.

Yeah, if you're going the drill route, you could just buy an electronic counter and jury rig it with a little snap switch. It'll be a little bit cheaper. It might cost you like, $20 instead of $35.

 

[Bruce Johnson]

I need to make up the tooling for the new Hot Split version of my AMB-2 Scroll Bass pickups. The Hot Split pickup has a different size outer housing than the previous standard (baseline?) AMB-2 pickup. The housing needs to be 1/8" taller in height to fit taller bobbins, which have more windings. And, I'm also dividing the pickup into two halves, one for each bobbin. Each half of the pickup can be individually adjusted for height and tilt to fine-tune the string-to-string balance. So, I need to make up new molds for the encapsulation/outer housings of this new pickup.

I make up the outer housings of the pickups by casting them in a silicone rubber mold. The perforated brass shielding shell and the completed coil are set down into the mold, and it's poured full of black West Systems epoxy. To make the silicone rubber mold, I first have to make up a Master. This is an exact-size form of the outer size/shape of the pickup, which the silicone rubber is poured over. I like to machine the Master from aluminum, carving it from an aluminum block.

Masters don't have to be made from aluminum. You can use wood or plastic or cardboard or even modeling clay. I like using aluminum for accuracy and permanence.

It's time to use my big machines, which is just plain fun! I start with a chunk of 2" square 6061 bar stock, clamping it in the vise of my big Kondia Milling machine. And the chips start flying! I mill away the front and back surfaces of the block, leaving a raised center section.

As I've said before, having a big milling machine is a necessary part of life. It makes things.

Milling small steps to rough out the 7 1/4" radius top surface.

Over to my big horizontal bandsaw, to saw off the section that I need.

And there's the rough-machined blank. In the background is the Master for the standard one-piece pickup. You can see how it's shaped and smoothed and polished. That's coming up for the new one.

 

[Bruce Johnson]

Finishing up the Master for the Hot Split AMB-2 pickup:

The next step is to drill the holes for the location dowel pins. These pins are used to accurately locate the aluminum base plate on the bottom of the pickup, during the casting process. I drill holes in the base around the master, accurately positioning them from the Qcad drawing data. I do this in my trusty green Mill/Drill machine with the digital readouts.

Next, I clamp it in the vise and file the lump of the Master to shape. By hand, with files. Just as if it were a block of wood. No stinkin' CNC's or 3-D printers here! I used a couple of big 14" files to rough in the half-radius on the top, then smaller files to smooth out the sides and gently radius the edges all around. I finish up with a #2 Swiss file. Then smooth it off to a satin finish with a Combi-Flap wheel in an electric drill.

And here's the finished Master. I didn't polish it up to a high shine; not necessary because the outside of the cast pickup gets all sanded anyway.

I plugged 1/8" x 1 1/4" steel dowel pins in the holes. When I cast the silicone mold, it will leave these deep 1/8" holes in the mold, in accurate relation to the shape of the pickup. Then I'll plug similar dowel pins into the mold itself, leaving them sticking up above the surface. When I cast the pickup, I'll place the aluminum base plate down over those pins, which will hold it in alignment with the pickup. There are four pins, but the split base plate half has only three screw holes. I put in the four pins so that I can use the same mold to cast both the right and left pickup halves, flipping over the base plates. You'll see in the coming steps.

 

[Freekmagnet]

Bruce - I have long admired your baseplates, and just to understand the depth of your pickup-making madness, did you cut those square holes by hand and clean them up with a file?

 

[Bruce Johnson]

Bruce - I have long admired your baseplates, and just to understand the depth of your pickup-making madness, did you cut those square holes by hand and clean them up with a file?

The first couple, yes. I used a template to scribe the outline of the square hole on the aluminum plate. Drilled a couple of holes in it, then cleaned them out to shape with a big square file. Using a big (like 14") square file on 0.090" aluminum plate doesn't really take long. A few minutes.

But, once I got the design established and started making the base plates in production, I bought a 3/4" square Chassis Punch. A very handy tool used by Electricians and electronics guys. I drill a 1/2" dia hole, assemble the chassis punch through the hole, tighten it with a wrench. And Pop, there's a nice neat square hole.

A new top-grade Greenlee 3/4" square chassis punch is about $200. I shopped around on ebay and found a lightly used one for $40.

Chassis punches are available in all sizes and shapes; round, square, rectangular, connector-shapes. They are made for cutting standard size holes in sheet metal, quickly.

 

[Bruce Johnson]

Continuing on with making the mold for the Hot Split pickups;

With the aluminum Master done, it's ready to be used to make the mold. I saw a 2" wide strip of 3/4" MDF, then cut it into four blocks that are fitted tightly around the base of the Master.

I coat the surfaces and ends of the blocks with Johnson's Paste Wax.

I assemble the blocks around the master on a strip of waxed paper, and hold it all together with clamps.

Mix up the silicone rubber mold compound, and pour it in around the master, up to the top edge of the blocks. It'll take about 12 hours to cure. This basic technique is how I make all of my molds. It works very well. I can pour as many molds as I want, to speed up production. I clean and store the Master and the blocks, ready to make up a new mold whenever I need it.