I decided before Christmas I wanted to have a go at making my own magnetic pickups, and put it on my to-do list for the new year. I studied this guide http://www.instructables.com/id/Make-A-Guitar-Pickup/ extensively and ended up taking inspiration from a few other sources to come up with a design, here is the process:
I ordered a 500g spool of 42awg (0.063mm) copper magnet wire from Brocott's (UK supplier) and a couple of packs of alnico 5 rod magnets (5x19mm) on eBay. I had some 3mm sheets of sapele so I figured I would use this for the bobbins.
These were the first 2 bobbins I finished, I fixed the magnets flush with the top and bottom with a dab of superglue and drilled 2 holes for the start and end of the wire. It is really important to sand the inner surfaces of the bobbins completely smooth and free of any tiny burrs as the wire will get caught. Best case scenario you'll have to unwind several hundred turns, worse case the wire will break and you'll have to start over.
This is the winding jig I made. I did try a sewing machine first but I felt that I didn't have enough control. This is just a hand-cranked drill clamped to a desk, with a block of wood fixed to a dill bit. I attached the bobbin with an adhesive pad. One turn of the handle is about 4.2 turns of the bobbin, so I would do 50 turns, check for any tangle or loose winds, then do another 50 and mark a tally. When I had done 19 x 100 revolutions of the handle, I had roughly 8000 turns on the bobbin. This took about 30 minutes altogether.
I then decided to make a hole in the soundboard of one of my guitars to check for the fit. I use a neck-through design so I also needed to chisel out a recess for the bottom of the pickup to sit in.
I used a drill to start the hole, then fed a coping saw through to cut it out, then sanded etc. I then realised I hadn't thought of how to mount the pickup, and after looking at pages of pickups on Google images, I decided to start over and go for a top-mounting design. (Thanks to Mr. Crocker - an endless source of inspiration!)
These were mark 2. I made the tops of the bobbins larger than the bottom, so I could screw them into the soundboard through the top, covering up the hole for aesthetic and acoustic reasons. I also replaced the holes for the start and ends of the coil with small screws. I used steel screws for these but I do not recommend it - it is very tricky to solder onto them - as you can see:
Hmmm... not looking too great. Soldering was very difficult as I needed to melt off the enamel coating on the copper wire before the solder would stick. However I checked the connections by attaching a jack and plugging it in and it did work! Next step was potting.
This is a double boiler I constructed to melt the wax. I put about 600g of parrafin wax pellets into a kilner jar, placed a block of wood underneath so the jar was not in contact with the heat source and lashed the top of the jar to the sides of the pan with rubber bands. I filled with water up to about 1" from the top level of the wax and used a meat thermometer to gauge the temperature (which needs to be about 65c). I should add that I have an electric hob, and I think this process would be quite dangerous with an open flame. (This is so far the only advantage to an electric oven I have ever found).
Once the wax had all melted, I wrapped the lead wires from the pickup around a screwdriver and rested it on top of the jar, so the pickup was suspended in the middle, not touching the sides. The idea here is to wait until the bubbles stop rising and the coil will be saturated. I should add that the wood I used also took in wax - and bubbles came off that too. I have it about 20 minutes, took it out, wiped the excess from the bobbin and let it cool. I then wrapped round some PTFE plumbers' tape to protect the coil.
Then it was time to wire it up and put it in the guitar:
As you can see, I attached the pickup with 4 small screws. The clamps are there because I had to re-glue the lid on the box.
I then strung it up and plugged it in.
Hmm... not much volume, and lots of buzzing. I replaced the bridge with a pencil, to make it much lower, and the sound was louder - the pickup was too far from the strings. I also had not grounded the strings (which is a whole other problem as my bridge and tailpiece are both wood. Back to the drawing board again!
As you can see from Ted's diagram, the ground wire needs to connect the pot with the strings. I am planning to replace my wooden tailpiece with a metal one.
This is the new pickup I made last night. As you can see the top of the bobbin is much thicker, 6mm this time (an offcut from a sapele fretboard). The termination screws are now brass, so will be easier to solder. I also used a craft knife this time to scrape off the enamel coating, so soldering should be much easier. My next step is to pot it in wax and then wrap it with some copper foil tape, which just arrived yesterday. I will solder a wire from the ground on the pickup to the outside of the copper tape (thanks Bob Harrison for this tip). This combined with grounding the strings should have much better results, so fingers crossed.
...so, the problem I was left with was that I hadn't grounded the strings and both my tailpiece and bridge are made of wood (and bone, neither great conductors!)
I decided to go for a pretty drastic solution. Here is the problem:
This is part of a hanging fixture ( one of the advantages of working in a department store, few though they are), I used a Dremel to cut it to the right size and drilled a few holes to mount it to the back of the guitar and 3 to hold the string ferrules. I have used bike spoke nipples for these. At 20p each at my local bike shop they're a lot cheaper than real string ferrules!
The idea was to solder a wire to the inside of the tailpiece and connect it to the ground on the back of the volume pot. What I hadn't considered is that it's bloody difficult to solder to stainless steel. I didn't have any flux to hand so I cheekily superglued a strip of copper foil tape to the tailpiece and soldered the wire to that... hopefully this will work!
So here's the new tailpiece. I actually never liked the original so wasn't too sad to see it go. The sound still seems to be just as nice so I'll take that as a success...
I soldered the wire onto the back of the pot and checked all the connections. I plugged it in and the loud continuous buzzing had all but gone! I now had a slight buzzing which went away when I touched the strings... after sending myself mad Googling this for a couple of hours I found a lot of conflicting advice, mainly:
Now I'm perfectly ready to accept that I'm not very good at soldering, as I have no previous experience with it. However I figure that if everything works, the soldering should be fine, right?
I eventually decided to believe number 2. I noticed that there was very little hum when I left the guitar in the middle of the room, and stood away from it. I also noticed that not having my amp plugged into a socket with a PC, Laptop and a baby monitor made a big difference. If anyone reading this has any other ideas I'd love to hear them!
So, I still had one last trick up my sleeve - my copper foil tape. I thought I'd give it a try on one of the new pickups I made following (I thought) Bob Harrison's suggestion.
So I have potted the coil, wrapped it in a few layers of plumbers' tape, and then wrapped in a layer of copper foil. I then ran a jumper lead from the ground connection (start of the coil) and connected it to the foil. I also used a little lump of solder to seal the foil shut in case the glue deteriorates over time.
Somewhat foolishly, I whacked the pickup in the guitar without checking it first... when I plugged it in, it didn't work. No signal, some buzz, but definitely no sound coming from the strings. Without really bothering to figure out why, I took it out and removed the copper foil (trying to grasp electronics by this point was making my head hurt). After ruminating on this over the last couple of days, I think that maybe I shouldn't have connected the ground wire to the foil and the start of the coil. If the ground is the path of least resistance, maybe I have just forced the current directly to ground... again, any feedback on this would be appreciated!
Sure enough, after removing the foil and the jumper lead, the pickup worked again. I strung it up, closed the access panels and called it a day. Some noise, perhaps, but hardly too offputting for a first attempt!
...and here's a video - let me know what you think!