Making Coils

[McSeem]

Hi, a couple of weeks ago, while waiting for the parts, I decided to make a sustainer coil. Since my goal is to make a truly hexaphonic sustsainer, I'll wind coils for each string. 6 of them, and, maybe, even 12. So, this is also my early experiment, I came up with just a single coil, that works perfectly and has proper parameters.

I took pole pieces from a cheap humbucker, but you can order them for a much lower price. You can also use alnico magnet poles for that. The reason I used just metal is to tweak the permanent magnetic bias, using different magnets. But if alnico works well, as I assume, it's even better.

So, you take a pole piece, you take a drill like that:

http://antigrain.com/hex_project/coils001.jpg

Well, there's a trick. You don't want your drill to rotate at its full speed. You need to adjust it. And you also don't want to hold your finger all the time to keep proper speed. So, what you gonna do? It's called TRIZ, http://en.wikipedia.org/wiki/TRIZ. I'm a big fan of TRIZ. I have a 300W lamp with a dimmer, and I just rewired two plugs, so that, they connect the drill and the lamp in series:

http://antigrain.com/hex_project/coils002.jpg

http://antigrain.com/hex_project/coils003.jpg

So, with the dimmer you can perfectly control the RPM and use your drill to wind the coils. And you also use it as a lathe machine!

Next, you saw the pole piece in the following way:

http://antigrain.com/hex_project/coils004.jpg

http://antigrain.com/hex_project/coils005.jpg

http://antigrain.com/hex_project/coils006.jpg

The tricky part is to accurately measure the height. But you can make a coil of any height you want, even 3mm or so.

Then you take a suitable plastic pack to make the washers. You cut them, stack, and drill a slightly smaller hole like this:

http://antigrain.com/hex_project/coils007.jpg

http://antigrain.com/hex_project/coils008.jpg

You also cut it of course, so that the washers would be approximately round. An octagonal shape is OK.

Then you slightly cut the hole and put them on:

http://antigrain.com/hex_project/coils009.jpg

http://antigrain.com/hex_project/coils010.jpg

And, of course glue them. I use Elmers Ultimate Hight Performance glue. Make sure to use vinyl gloves, because this glue is really bad for your fingers.

The tricky part is to set up the washers as perpendicular as possible. I use a toothpick, while rotating the drill:

http://antigrain.com/hex_project/coils011.jpg

And then you gently remove it trying not to touch the washers. You can use a magnet for that, with a combination of plastic tweezers.

http://antigrain.com/hex_project/coils012.jpg

The next day, when the glue dries, it's time to lathe the plastic and wind the coil.

http://antigrain.com/hex_project/coils013.jpg

It can be dangerous for your fingers and your eyes! So, do it at your own risk! Eyeglasses are MANDATORY!

After that, you insulate the core with a piece of plumbing seal tape. It's very thin and provides enough insulation:

http://antigrain.com/hex_project/coils014.jpg

http://antigrain.com/hex_project/coils015.jpg

You gently tighten it with a piece of plastic, while the bobbin is rotating.

Then I use the very same drill to wind the coil:

http://antigrain.com/hex_project/coils016.jpg

http://antigrain.com/hex_project/coils017.jpg

http://antigrain.com/hex_project/coils018.jpg

Well, I admit it could be more accurate, but as the practice shows, it works perfectly. The modern magnet wires have very reliable insulation, so, don't worry too much about potential shortcuts and the accuracy. The only problem is how to count the winds. With the drill I have no good solution for that. If you wind it manually, you can use a simple step counter, put on your hand. It works perfectly. But with the drill it's not that simple. I didn't count the winds at all. Just I assume that 10-15% of difference is OK. I'm anyways going to adjust the response with the amp gain, since I will have 6 individual channels. So, more or less the same physical size is good enough to me. I used 36 AWG wire, and with this size, 6mm polepiece, about 4 mm space between the washers, and 10mm outer diameter, I've got almost exactly 10 ohms of DC resistance. It drives the string perfectly at about 4-5 mm distance. Well, after attaching the magnet you will have about 8 mm height, which is still OK in my case. I still have about 1.5 mm extra for the underneath binding, without having to mill a cavity. But once again, with this homemade technology you can wind coils of any size, 3 mm if you want. You can also use thiner plastic.

The only thing is left is to cut it off. I use the very same drill and the very same metal saw:

http://antigrain.com/hex_project/coils019.jpg

http://antigrain.com/hex_project/coils020.jpg

http://antigrain.com/hex_project/coils021.jpg

It may look very hard to make, but if you make a number of coils, at least 6 of them, it takes about an hour per coil. Well, plus the time to let the glue dry, of course.

So, enjoy with homemade engineering, as I do! My girlfriend does not appreciate it, though... :-)

[verhoevenc]

Dude, this is SUPER cool! SUPER cool!

Chris

[Fresh Fizz]

Hi, a couple of weeks ago, while waiting for the parts, I decided to make a sustainer coil. Since my goal is to make a truly hexaphonic sustsainer, I'll wind coils for each string. 6 of them, and, maybe, even 12. So, this is also my early experiment, I came up with just a single coil, that works perfectly and has proper parameters.

Nice tutorial! Should be a sticky thread.

So if I understand you well this hexaphonic sustainer driver will eventually replace the neck humbucker?

Well, I admit it could be more accurate, but as the practice shows, it works perfectly. The modern magnet wires have very reliable insulation, so, don't worry too much about potential shortcuts and the accuracy. The only problem is how to count the winds. With the drill I have no good solution for that. If you wind it manually, you can use a simple step counter, put on your hand. It works perfectly. But with the drill it's not that simple. I didn't count the winds at all. Just I assume that 10-15% of difference is OK. I'm anyways going to adjust the response with the amp gain, since I will have 6 individual channels. So, more or less the same physical size is good enough to me. I used 36 AWG wire, and with this size, 6mm polepiece, about 4 mm space between the washers, and 10mm outer diameter, I've got almost exactly 10 ohms of DC resistance. It drives the string perfectly at about 4-5 mm distance. Well, after attaching the magnet you will have about 8 mm height, which is still OK in my case. I still have about 1.5 mm extra for the underneath binding, without having to mill a cavity. But once again, with this homemade technology you can wind coils of any size, 3 mm if you want. You can also use thiner plastic

.

But until now you only have driven the strings from above (like an E-bow)? I don't want to sound negative but if you're going to drive from below using too much power could become a problem (string rattling).

Cheers

FF

[McSeem]

So if I understand you well this hexaphonic sustainer driver will eventually replace the neck humbucker?

Not necessarily, I may try to put it directly on the body. On the other hand, I have a feeling it's nice to have individually adjustable height. So, we will see. Maybe I'll use the neck HB space, maybe I'll mill another cavity. But first I'll try simplest ways.

But until now you only have driven the strings from above (like an E-bow)? I don't want to sound negative but if you're going to drive from below using too much power could become a problem (string rattling).

.

That's OK, you can sound as negative as you want :-)

I'm aware of this problem, and as I said, I'm going to use a lot of processing in software - pitch detection, automatic phase adjustment, depending on the string and the note, and so on. Not sure I can achieve anything, but I'll give it a try. And, of course, I can dynamically change the gain to start the sustain quicker, and keep it under control: if the amplitude is getting too high, I just reduce the gain and balance the signal - it's easy to do in software. In general, I noticed that a dynamic range compressor helps a lot and makes the sustain feedback almost perfectly stable. So, I'm going to use some compression too. It's even more complex. I'm going to try a very fancy response characteristic, an expander at low signal levels (or, even a threshold), and a compressor at high levels. It should prevent the strings from autoexcitation.

With a simple, but powerful amp, the system, as a very high-Q one, can easily get out of control. And yes, I nearly burnt the coil. :-)

McSeem

[lvs]

But if alnico works well, as I assume, it's even better.

Just a thought : the pole piece you shaped is probably soft iron, while alnico, which is very hard and brittle, would be a quite different machining story. Anyway, keep those safety goggles within reach.

Pedantic mode off now, and thanks for sharing your project.

Cheers

Lucas

[McSeem]

Just a thought : the pole piece you shaped is probably soft iron, while alnico, which is very hard and brittle, would be a quite different machining story. Anyway, keep those safety goggles within reach.

Right, I just forgot about it. For alnico you have to use real plastic bobbins. BTW, it's also possible to lathe bobbins from a suitable plastic rod, using just my homemade lathe drill. It's more tricky, but quite possible.

I tried to request for a quote at ablecoil.com (for hex pickups), it costs more than gold:

The request:

I need a number of self-supporting coils, with the following parameters (approx):

Internal diameter: 3.2 mm

External diameter: 8 mm

Height: 12 mm

DC Resistance: 400-500 ohms

The response:

The cost will be a $500.00 lot charge for the 10-20 coils, plus $1,000.00 for the tooling.

Lead time will be 10 weeks.

So, it only makes sense to order a 1000 or so.

BTW, are there any places to make custom coils for a reasonable price? It's OK to DIY coils for experimentation, but becomes unreasonably tedious, when you come up with the parameters and want to make many copies for production.

McSeem

[McSeem]

I assume Ive got you with my posts, I accidentally found a nylon spacer of 10 mm outer diameter and decided to make a bobbin. It's good, but it's really hard to lathe nylon with just a drill and files. Much harder than iron; nylon is very slippery. But I could wind a much nicer coil and with the 36 AWG wire it has 8.8 ohms DC resistance.

So, how it looks:

http://antigrain.com//hex_project/coils022.jpg

http://antigrain.com//hex_project/coils023.jpg

http://antigrain.com//hex_project/coils024.jpg

http://antigrain.com//hex_project/coils025.jpg

Then I tested it, also with the Guitar RIG and VERY fancy virtual devices, like that:

http://antigrain.com//hex_project/GuitarRig01.jpg

It sounds crazy and also drives the strings like mad. It also tends to produce a lot of squealing harmonics even on low strings. I could never imagine that you can so easily excite 10th or even 15th harmonic. And, no, there's no direct feedback, I used the saddle pickups.

http://antigrain.com//hex_project/sus05.mp3

I fed the coil with the very same signal you hear. Of course it's now all random; no phase coherence, no rocket science, but it proves that some fancy processing may make sense.

McSeem

[Geo]

Those arpeggiated harmonics sound amazing! Does your design do that automatically, or is that in the signal processing, or is it in your playing technique?

Bravo, regardless!!!

[McSeem]

Yes, there's a lot of sound processing. As I said, it's Guitar RIG 4, with a pre-set called "Arpeggio Delays". This is a screenshot:

http://antigrain.com//hex_project/GuitarRig01.jpg

But the combination with the sustainer coil sounds REALLY fancy.

[col]

nice coil building method