This pickup incorporates a simple bobbin design, cheap magnets, and thicker than standard wire. This makes it easy to construct in a simple yet precise design. It also looks pretty cool. However, the output is much lower than standard passive pickups, not nearly enough to drive a pickup through a long cable. It requires a simple and inexpensive op-amp to boost it’s signal, essentially turning it into an active pickup. The coil also has less impedance than a standard pickup, meaning it will need custom tone shaping controls. It is not as complicated as it sounds, especially if you have some knowledge of electronics.
Step 1: Get What You Need
tools I used:
electric drill w/ bits
ruler and marker
soldering iron or 'pencil'
clear postal tape
clear cellophane tape
clear plastic (not Plexiglas)
1” long flat head bolts w/ nuts and washers
male slide connectors
8 ceramic magnets (mine are 1cm wide, 1.5cm long, 4mm thick)
a spool of small diameter enamel coated copper wire
soldering flux (optional)
small diameter rosin core solder
The magnets were given to me by a friend. He got them from someone who owns some type of printing/graphics company. The clear plastic I bought for fifty cents in the office supplies section of a second hand shop. It isn’t Plexiglas, it is what I would call acrylic. It doesn’t shatter like Plexiglas, and is much easier to machine. Of course any plastic, wood or even cardboard could be used, so long as it is not metal and is stiff enough to not flex much when you tighten the bolts. You could also just glue the top and bottom pieces to the magnets, and eliminate the need for bolts. I didn’t go that route because I was going for a see-through look and glue would have messed it up. Besides, the bolts also provide a very good anchor for the ends of the coil. I got them from a hardware store. I got my wire from the coil of an AC synchronous fan motor.
Step 2: Know Your Stuff
Many guitarists, especially the young or uninitiated, may look upon the electric guitar as some kind of black magic. I myself drooled on them without having the slightest idea about how they worked. For this project it will help if you have some idea how pickups work.
Electric guitar pickups convert the mechanical energy of vibrating guitar strings into electrical energy. This weak electrical current can be amplified and then pumped through speakers.
In their simplest form, they consist of a coil of copper wire wrapped around a permanent magnet(s). Traditional pickups use thousands of turns of very fine (usually 42 gauge) wire that is wrapped around a plastic bobbin. Six permanent magnets, called pole pieces, are then slid up inside of the bobbin.
Because your guitar’s strings are made of magnetic metals (usually steel or steel wrapped in nickel), the parts of your strings above the pickup become slightly magnetized. When you pluck a string, the string and the magnetic field surrounding it vibrate. This induces an electrical current in your pickup’s coil. This is due to the fact that the magnetic field surrounding the moving string drags electrons in the coil with it as it moves. The current generated is alternating current, because the electrons move one way, then the other (just as the string does), creating a voltage that changes polarity.
There are several reasons why I did not try to replicate a factory made pickup:
First, 42 gauge copper wire is hard to work with. It’s about as thick as human hair. Winding thousands of turns on a bobbin is tedious and time consuming. A slight deviation in tension while winding your pickup and it breaks, creating a major setback. It is difficult to solder. It is hard to scrounge enough of it from junk(though if you want to try, the best sources I found are AC synchronous motors, like the kind used in the electromechanical timers of some, usually older, analog appliances).
Secondly, the magnets of pickups are usually super magnets, which are expensive for a cheapskate like me. I had no luck scrounging any in the right shape.
My solution is to simply use thicker wire. Not a lot thicker, but a gauge somewhere in the mid to upper 30s. I wound it around ceramic (ferrite) refrigerator magnets. It makes everything easier.
Step 3: Begin Building Your Bobbin!
First I took the magnets and taped them together. I took a piece of postal tape and stuck it to my table with the sticky side up (with the ends folded underneath and stuck to the table). I then took the magnets in stacks of two and stuck them on the tape end to end. Make sure that the magnets all have their poles facing the same direction. For me that meant having a compass to check polarity, placing the magnets so that their north poles were down and south poles were up. Which pole is up or down doesn’t matter. The magnets will fight you, and generally try to stress you out, but stick them to the tape and then fold the tape up onto their sides. For appearances I didn’t wrap the tape over the top, just the bottom and sides. Trim excess tape with scissors.
Step 4: Cut Out Plastic
Next, I cut out my plastic. Go slow and be very precise on the next few steps. If you feel yourself getting impatient then either take a break and/or fill a bucket with cold water and stick your head in it! Otherwise you are well on your way to creating a crumby pickup, which is very discouraging.
My plastic was already the right width, 7/8”, so I put it in my vise between two pieces of cardboard and cut it with a hacksaw. The length you are going for is 3 1/4”, so cut it a little long and then take it out and grind it to the precise length with a bench grinder. Also, grind the corners at a forty-five degree angle until you have turned the corners into sides that are 1/4” long.
Step 5: Drill! (Carefully)
Drill the holes for the bolts with a 9/64ths drill bit so that they are 6.4cm apart from center to center. Make sure they are otherwise centered on your piece. I drilled the holes in another piece of plastic first, then once I knew I had it right I used it as a template to mark the piece I was going to use. Then I drilled it, stacked it with the second piece and ran the drill through the first piece and the second. This will ensure that your holes line up properly and your bolts will slide through. Wrap cellophane tape around the bolts and stick the ends to the sides of the magnets. Now your pickups are ready to be wrapped with wire, which is the next step.
Step 6: Almost Ready to Wrap...
One difficulty is the transition from the tiny wires of the pickup’s coil to larger hookup wires. The best way I found is to make some sort of post on the pickup itself that both can be soldered to. I found some brass pieces from a microwave that slide connectors attach to. Holding them in my vise I drilled holes in them, cut them in half, and bolted them on the bottom of my pickup.
Next, I assembled the pickup. Look at the pictures to help you.
Step 7: Winding!
Next, wind the pickup. You have a choice between winding your pickup completely by hand or using a motor to assist you. I tried various things, but came back to something I cranked by hand. If you have a sewing machine with a flywheel, I suggest you use that. The only difficulty is in attaching the pickup to the flywheel. The best solution for me was to stick magnets to the flywheel, then tape a cardboard jig to the flywheel over that. The magnets hold the pickup to the flywheel, the cardboard jig keeps it from sliding. You can see the crumby jig I made in the picture. I used clear cellophane tape to control the wire at the beginning and the ends of the wire. I'm sorry that this part of the instructable is a little skimpy, refer to other intstructables or how tos for more details.
Step 8: Solder, and Your Pickups Are DONE!
Solder the ends of the wire to the brass (see picture). I found that burning the insulation off the wire with a candle flame to work well. I also used a little flux, but it isn't necessary.
Okay, now you are ready to put your pickups to work. I hope to add to this instructable when I get the next step, which is filtering and boosting the signal with op-amps, soon.