Magnets & Copper Wire: A Pickup Building Thread

[Freekmagnet]

I decided to try some laser cut parts vs cutting my own flatwork and baseplates. These are from ponoko - laser cut acrylic. The order came much more quickly than the estimated time, and buying a bunch at once made them fairly cheap. I have yet to use any of these but I'm happy so far. Assuming no surprises, I think I'll continue to do the same thing I did for these designs - make a prototype myself "by hand" and then get a bunch cut once I'm happy with the design.

This is a bunch of bobbin flatwork and baseplates for ukulele humbuckers, plus some bobbin flatwork for the blade style split coil bass pickup I posted about several pages back.

View attachment 4216719

I like Ponoko. The files are easy to set up and submit, and their prices are good. However, I’ve waited over a month for delivery more than once. I also get my flatwork cut by Ponoko. For the cost, Ponoko is inexpensive enough so that it’s pretty pointless to cut it myself.

 

[slowburnaz]

I like Ponoko. The files are easy to set up and submit, and their prices are good. However, I’ve waited over a month for delivery more than once. I also get my flatwork cut by Ponoko. For the cost, Ponoko is inexpensive enough so that it’s pretty pointless to cut it myself.

If I remember correctly, they even do vulcanized fiberboard...

 

[Freekmagnet]

If I remember correctly, they even do vulcanized fiberboard...

They do, actually. I get my vulcanized FB cut there. Their prices are very reasonable.

 

[dwizum]

Somehow I missed that they do vulcanized fiberboard. I just ran some of my files and I think I'll stick with acrylic, for now at least. The fiberboard was more than three times the cost. At that point I think I'd just buy my own laser.

Speaking of cutting things, I can confirm what @MPU said back in January about cutting ceramic bar magnets. It's easy! I rigged up a vise in front of a shop vac hose with a little carboard "hood" to direct every possible spec of dust into the vacuum, then I scored the magnets with a dremel cutoff disc. It really didn't take much at all and the magnets snapped along the scored line very easily. Three of them actually just snapped as I made the score, even though I was using very light pressure with the dremel. The 4th I snapped like breaking a piece of dry spaghetti. No prob, even a very faint score makes it break easily.

I did this for a split coil Jazz pickup design featuring steel slugs. I bought 3.15" long by 1/8" x 1/4" bars and cut them in half so I could reverse the polarity of each of the slugs and get each pickup hum cancelling.

I'm confident enough in these that I'm gonna go ahead and pot them before I even sound test.

 

[Freekmagnet]

Somehow I missed that they do vulcanized fiberboard. I just ran some of my files and I think I'll stick with acrylic, for now at least. The fiberboard was more than three times the cost. At that point I think I'd just buy my own laser.

Speaking of cutting things, I can confirm what @MPU said back in January about cutting ceramic bar magnets. It's easy! I rigged up a vise in front of a shop vac hose with a little carboard "hood" to direct every possible spec of dust into the vacuum, then I scored the magnets with a dremel cutoff disc. It really didn't take much at all and the magnets snapped along the scored line very easily. Three of them actually just snapped as I made the score, even though I was using very light pressure with the dremel. The 4th I snapped like breaking a piece of dry spaghetti. No prob, even a very faint score makes it break easily.

I did this for a split coil Jazz pickup design featuring steel slugs. I bought 3.15" long by 1/8" x 1/4" bars and cut them in half so I could reverse the polarity of each of the slugs and get each pickup hum cancelling.

View attachment 4233329

I'm confident enough in these that I'm gonna go ahead and pot them before I even sound test.

C8 split J HB? Niiiiice!

 

[slowburnaz]

C8 split J HB? Niiiiice!

Kinda like a Model J. I like!

 

[Bruce Johnson]

Somehow I missed that they do vulcanized fiberboard. I just ran some of my files and I think I'll stick with acrylic, for now at least. The fiberboard was more than three times the cost. At that point I think I'd just buy my own laser.

Speaking of cutting things, I can confirm what @MPU said back in January about cutting ceramic bar magnets. It's easy! I rigged up a vise in front of a shop vac hose with a little carboard "hood" to direct every possible spec of dust into the vacuum, then I scored the magnets with a dremel cutoff disc. It really didn't take much at all and the magnets snapped along the scored line very easily. Three of them actually just snapped as I made the score, even though I was using very light pressure with the dremel. The 4th I snapped like breaking a piece of dry spaghetti. No prob, even a very faint score makes it break easily.

I did this for a split coil Jazz pickup design featuring steel slugs. I bought 3.15" long by 1/8" x 1/4" bars and cut them in half so I could reverse the polarity of each of the slugs and get each pickup hum cancelling.

View attachment 4233329

I'm confident enough in these that I'm gonna go ahead and pot them before I even sound test.

A cool design and construction technique!

I haven't played around with blade-type pickups (yet), but I've had an interesting thought: What if you were to turn your pickup upside down? Put the ceramic bar magnets on the top of the coils, directly under the strings. Same construction as you've done, with the blades hanging down through the coils. I'm thinking that would make an extra efficient shape of the magnetic field. The dense powerful upper lobe wrapped right around the strings, and the long lower lobe around the blades and coils. I can't see why that wouldn't work. Maybe try a quick experiment before you get them all potted and sealed up?

 

[dwizum]

Bruce as always you are a genius! That makes a whole lot of sense. I will try it both ways and report back. I'm pretty confident they will sound good in "regular" mode, based on the fact that they're very similar in many ways to other blade pickups I've made, but I would like it if I could get some extra oomph out of this design, and especially a fatter tone than a regular Jazz pickup, if that makes sense, since that was the whole goal of this design.

I'll need to notch or drill the flatwork to allow the wiring to pass through and still fit in the cases when in "upside down mode" but that should be pretty straightforward and there's plenty of clearance. I need to rewind one of the four coils first though, I did a continuity check prior to potting these and there's a really high resistance fault between one of the coils and the steel slug. I cover the slugs in tape prior to winding but maybe my tape job was sloppy and/or the coil wire got the insulation partially cut as I wound, or something. The coil is spot on in terms of resistance so the wire seems intact, must just have a weak spot in the insulation right on the slug somewhere where it didn't get covered with tape or something.

I haven't made labels for these yet. I was going to just call them something boring like "Jazz Split Blades" but if this upside down idea works, I think I'm going to need something more creative than that.

 

[Slidlow]

Bruce as always you are a genius! That makes a whole lot of sense. I will try it both ways and report back. I'm pretty confident they will sound good in "regular" mode, based on the fact that they're very similar in many ways to other blade pickups I've made, but I would like it if I could get some extra oomph out of this design, and especially a fatter tone than a regular Jazz pickup, if that makes sense, since that was the whole goal of this design.

I'll need to notch or drill the flatwork to allow the wiring to pass through and still fit in the cases when in "upside down mode" but that should be pretty straightforward and there's plenty of clearance. I need to rewind one of the four coils first though, I did a continuity check prior to potting these and there's a really high resistance fault between one of the coils and the steel slug. I cover the slugs in tape prior to winding but maybe my tape job was sloppy and/or the coil wire got the insulation partially cut as I wound, or something. The coil is spot on in terms of resistance so the wire seems intact, must just have a weak spot in the insulation right on the slug somewhere where it didn't get covered with tape or something.

I haven't made labels for these yet. I was going to just call them something boring like "Jazz Split Blades" but if this upside down idea works, I think I'm going to need something more creative than that.

I think you'll lose focus with the magnetic field if you place them on top. Not sure if that would be desirable or not so yes to experimentation.

 

[Bruce Johnson]

I think you'll lose focus with the magnetic field if you place them on top. Not sure if that would be desirable or not so yes to experimentation.

What do you mean by lose focus? The way I'm picturing it, you'd be putting the string right in the most dense, uniform area of the field, which I would think would increase clarity and definition? Plus, you'd be widening the aperture along the length of the string.

Maybe there's some reason why it wouldn't work, but it seems like it would be a better use of the shape of the magnetic field.

Dwizum, I'm suggesting a quick experiment with your blade pickup assembled as it is. Hold it upside down under the strings in your bench mule, and see what it does. If it's interesting sounding, you could build another one using the same components, just assembling it so the ends of the blades stick out the top. And put the magnets on top of the coils.

 

[A9X]

I will try it both ways and report back.

I'll watch with interest too.

 

[Slidlow]

What do you mean by lose focus? The way I'm picturing it, you'd be putting the string right in the most dense, uniform area of the field, which I would think would increase clarity and definition? Plus, you'd be widening the aperture along the length of the string.

Maybe there's some reason why it wouldn't work, but it seems like it would be a better use of the shape of the magnetic field.

Dwizum, I'm suggesting a quick experiment with your blade pickup assembled as it is. Hold it upside down under the strings in your bench mule, and see what it does. If it's interesting sounding, you could build another one using the same components, just assembling it so the ends of the blades stick out the top. And put the magnets on top of the coils.

I'll let you figure it out.

 

[A9X]

I'll let you figure it out.

How about some hints for us beginners?
My thoughts; as the detection area is the steel strip, with the magnets now much closer to the strings, would that not to some extent damp the string motion (small effect as HBs are like this anyway) but give it a wider, along the string, magnetic field yet still a small detection window?

 

[dwizum]

Well I think the result is going to be both confusing and anticlimactic.

I was too excited to bother with putting it in the case or screwing it in, so I taped it into the bass with masking tape.

I tried it "right side up" with the blade pointed at the strings and the magnets on the bottom. I then tried it upside down - magnets at the top. Finally, for the heck of it, I tried it sideways, since the pickup is basically a 5/8" square profile.

And... drum roll please....

I practically couldn't tell a difference.

I mean, there IS a difference. A really, really subtle difference. After swapping 14 or 15 times (really!) I could pick out an ever so slight difference. The difference was really in the attack more than anything. "Upside-down" made the attack feel a hint more aggressive - not really louder - just clearer, if that makes sense. It gave the pickup a woody character. It was such a subtle change that it took really careful back to back listening to tell. Sideways made the attack a hair softer and gentler. And right side up had a kind of in between attack.

The differences vanished if I used the soft pad of my thumb and played further up towards the neck. It was really only noticable using the hard callouses on my fingers and plucking more aggressively.

I guess the good news is, I really like these as-is. I'm going to stick them in the cases "right side up" and call it good.

Also - my test bass has zero shielding in it, on purpose, so I can have a worst-case sense of how noisy a pickup will be. These are 100% dead silent, I guess as would be expected for split coils!

 

[Beej]

Hilarious!

 

[Bruce Johnson]

Well, that's very interesting! Your experiments would seem to indicate a couple of things:

1. When the string wiggles within the magnetic field, the magnetic field picks up that motion and the whole magnetic field wiggles as one. I had wondered whether the lobes on opposite sides of the magnet were connected together. That is, if you wiggle the field on one side of the magnet, does that make the field on the opposite side also wiggle? It appears that the answer is yes. When you tested this pickup rightside up, the string and coil were both on one side of the magnets, within the same lobe. Upside-down, they were in different lobes, on opposite sides of the magnets. But the signal levels and sound were approximately the same. Huh. That would seem to mean that the whole field moves together as one when it wiggles. Right?
2. It doesn't look like positioning the string in a denser part of the field matters as much as I had thought. I had guessed that the upside-down position would be louder (higher output level) because the string was much closer to the magnets, in a much denser part of the field. Huh. Does the density of the field around the string not matter so much in how much the string's motion can make the field wiggle? Or is it that the density at the tip of the blades is actually nearly the same as the density right near the magnets? What about at the side of the coil?
3. Also, this experiment makes it look like the direction of motion of the string in relation to the direction of the wire turns in the coil doesn't matter much. With the coil on its side, I'd expect the output level to be lower. Huh. Maybe we should think of the field's motion as a cylindrical rolling, rather than a side-to-side wiggling?

Hmmm. The mysteries of how electro-magnetic pickups really work.....

 

[dwizum]

I guess there is essentially a distillation from three dimensions (string moving in a magnetic field) to one (current in a wire). I guess the formula that makes that distillation is independent of "where" in the field the disturbance happens, more or less?

I am also wondering if human ears are sensitive enough to be a good measurement device in this test. There could, technically, be big changes in signal strength (but keeping relatively the same "profile" in terms of tone) without me noticing.

It's starting to sound like tone is really dependent on the design of the pickup, and not on the relationship between the pickup and the string. And output level is dependent on both. Does that sound right to everyone? I know it's conventional wisdom that "sensing length" in terms of the amount of string that's in the field is important to tone. I don't think I have disproved that, because I don't know if we can really say for sure if my tests had significantly different sensing lengths on the string(s). I feel like I know so little about how a steel slug shapes the field that it's hard to answer that. I know the "basic" theory, but we need to know the details, I'd think.

I feel like I want to do some more experimenting, maybe record some samples in and look at their shapes. Not even listen to them at all, just look. I wish there was a more consistent way to excite the strings other than plucking them with my meat sticks.

Someone else should put a pickup in a bass upside down and see what happens, I don't want this to be all down to me in case I'm doing something stupid and not realizing it!

 

[A9X]

I wish there was a more consistent way to excite the strings other than plucking them with my meat sticks.

An electromechanical or even straight mechanical plucker wouldn't be too difficult. A hard object like a pick would give the sharpest leading edge to the impulse and widest bandwidth.

 

[Freekmagnet]

 

[dwizum]

I'll just go ahead and whip one of those up then. In my spare time.