Making up the spool coils:
I cast two of the top halves, with the terminals, and then two of the bottom halves; same mold but without the terminal wires. And those are the 3/8" x 1" A5 magnets.
I assembled the bobbin halves on the magnets, a light press fit, leaving about 1/4" of the magnet sticking out the bottom end. That becomes the mounting lug.
I made up an aluminum disk adapter for the spindle of my coil winder machine. It has a 3/8" hole and a setscrew that locks onto the end of the magnet. A simple and secure way to mount the bobbin onto the spindle.
I put a quick wrap of Scotch double sided tape around the center of the bobbin. I've found that having that sticky side out helps to get that first layer of the winding stuck down and even.
Winding the coil. I put on 8000 turns of #41, tight and even. It looks like there's space enough on the bobbin to put on 10,000 or even 12,000 turns, if I ever want to.
I stuck the coils onto a steel bar and terminated the coil wire ends onto the terminals. About six wraps around the terminal, leaving some slack in the lead-in, and then gently soldering it. And checking the continuity with the meter. Each coil ended up at 1.9K, about where I wanted them.
Potting the coils, dunking them for several minutes in Total Boat Clear Penetrating Epoxy. Having the magnet in the center is handy. I used that bolt as a handle for the dunking, and then stuck them on the steel bar to dry.
After the potting epoxy cured, I wiped on a coat of West Systems epoxy to put a hard protective shell over the coil.
I machined up a quick aluminum mounting bracket to fit the coils into the Ramirez. The coils are attached by the magnet end, a 3/8" hole and a setscrew.
Adding the leads. These two coils are full humbucker; the magnets are opposite, and the coils are wired opposite. I didn't put outer shielding shells on this pair of coils, but I will probably put them on the next set that I make. Perforated brass and black epoxy, like I do on my AMB-2 pickups. Total resistance is 3.8K.
Installed in the Ramirez. It's down directly under the bridge, with the coils under the two steel diaphragms. The two shiny cap screws adjust the height of the coils to get the right clearance under the diaphragms.
If you aren't familiar with them, this is a Baby Bass built by Ray Ramirez in Puerto Rico. It's similar to the classic Ampeg Baby basses from the '60's. It belongs to my buddy Juan Perez, who is my Chief Test Pilot. The original pickup worked, but it was weak (low output level) and thin sounding. So, Juan asked me to make up an upgraded replacement. I agreed to do it because I was planning to develop a better spool pickup coil anyway, for those other two electric upright bass projects.
Juan called me this morning. He played a long Salsa gig with the Ramirez last night in a big club. A big band of old pros. He said the Ramirez sounded great, and they all commented on it. Much fuller sound, more clearer bottom end, less mid-range honk. Juan's very happy with it. A successful upgrade.
