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El Apache: New Distortion Pedal Project

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Artwork for El Apache distortion pedal

I’ve gotten a little sidetracked from my usual pickup and bass building. My 15-year-old nephew, who is learning to play guitar, wanted a stompbox. I figured it would be a fun surprise to build him a little distortion pedal.

Being more of a bass player, I’ve build plenty of envelope filters and preamps but I’m not really well-versed in the world of guitar-effects such as distortion, fuzz and overdrive. I asked around, and a few people recommended the Electra Distortion. After doing a little research, I built one up on the breadboard and added a Baxandall tone stack and a buffered recovery stage to the end of it. I upped the gain a little bit as well. It sounds really good!

Here’s a little clip:

I designed a little PCB board in Easy EDA and sent the files off to the fabricator. I should be getting those in a few weeks. In the meantime, I designed some graphics for the face of the pedal. I took an image from the Mexican Loteria game. The li’l lady is Mexican and friends and family come over all the time to play Loteria. She and my nephew’s side of the family consider themselves Native Americans, so my nephew will get a kick out of the artwork.

This is a really cool pedal. I’m really excited about this little side project. I can’t wait to see this one come together. I’ll have a couple extra boards as well, so I’ll probably build up all three pedals.

New Preamp and Pickup Wind

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OK I’m just going to post a weekly update – no pix today.

I’ve been working on the pickup and preamp. Using my new cardboard bobbins I wound a couple of coils with 44awg wire and increased the wind count. I after casting them I mocked up a pickup with the new ceramic 8 cores. From there, I rebuilt my preamp using a James tone stack instead of the Big Muff/Tilt tone stack.

Two things:

1) On one of the cast bobbins, I somehow didn’t add enough hardener to the epoxy resin. I think that’s a pitfall that comes with mixing tiny 10ml quantities – if you’re off by just a tiny bit, that turns out to be a lot. Anyway, the piece didn’t cure and came out kind of rubbery. It’s good enough for testing, but not for a finished pickup. In the process of experimenting with various ways to build and cast my modular coils, I used all the pre-cut cardboard flatwork (I only ordered 14 pc to start). I ordered some more – it should be on its way soon.

2) I changed the preamp to a James/Baxandall tone stack because while the one-knob preamp was kinda cute, there just wasn’t any real control over the tone. Once you added any treble, you started to cut bass and vice-versa. With the James/Baxandall I’m able to fine tune the amount of highs and lows. I was even able to fine-tune the circuit itself by bumping 400Hz up by about 2dB. I also upped it to 18v much more headroom.

I know I’ve said this before, but this new pickup and preamp combo is a huge improvement. Keep in mind, pickup design is kind of a long process of experimentation that isn’t all that straightforward. In any case, the C8/44awg sidewinder rendered a much more controlled-sounding pickup. No more crazy high mids from the neos and with the ceramics wrapped in all that stainless steel, the biting highs are in the right place – nicely placed on top of a big cushion of clear lows and warm mids. With the neo versions, I felt like I was always struggling to contain this beastly pickup with these upper mids that just didn’t want to behave. Now I can really dig in to the strings without having to worry about it topping out.

I think it’s possible to design a really good-sounding neodymium pickup. I don’t know that the sidewinder design is the best application. I think maybe a more conventional humbucker with a steel core and the magnets placed on the bottom of the pickup might be a better approach with the neos. That keep the super strong neos away from the strings would make the magnets have to permeate all the way through the steel core. I dunno, just theorizing.

Back to Cardboard

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After all the different pickup-making techniques I’ve experimented with along this particular journey, I’m back to making cardboard bobbins.

Why, you ask? Well, first of all the bobbin flanges need to be very thin. Like .02”. I was using Garolite and FR4 before, but I was using cylindrical pole pieces; drilling 1/4” holes into the flatwork is relatively easy. The ceramics are bar magnets – cutting nice slots into the Garolite or FR4 by hand is no fun. No fun at all! I figured I’d get those pieces laser-cut ‘cuz it’s pretty cheap. However, there was a monkey wrench in my plan! Most of the stiffer industrial plastics they have available at the hobby-grade laser cutting places are things like Delrin or polypropylene and they are resistant to glues and such. Other plastics they had aren’t chemical resistant. I called around, and none of them seem to want to cut FR4 and stuff like that.

So, cardboard. And that’s fine. It’s easy to glue and the bobbins are really easy to make. I just cut a 3/16” strip of stiff architectural paper, wrap it around a magnet that I use as a form, and tack it on to the pre-cut bobbin. Plus, the pre-cut cardboard flatwork is cheap – like 20¢ each.

The only downside is that it’s not very strong and the bobbins are prone to flaring. I may have to do a slightly looser wind with 44awg instead of 43 – which I think will be OK. I don’t think it’ll change the sound enough so that it will be a deal-breaker. I dunno – I’ll experiment with that.

Bruce showed me these things he’d made to sandwich his bobbins onto his winder. I’ll have to make something similar to keep the bobbins from flaring. I’ll coat the sandwich thingies with wax and leave the wound bobbins in there while I apply the Penetrating Epoxy Sealer. Once that hardens for a day or two, I can take them out. Theoretically, the copper wire and cardboard bobbins will be just one hard happy lump of epoxy-coated goodness.

After that, I gotta make a new master for casting. The old one, pictured below was made for cylindrical magnets. I need to cut one with a slot. Using the limited tools I have at my disposal will make this an interesting project to say the least!

Circuit Build

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My circuit boards finally came in from the fabricators a few days ago. They’d been delayed and sent to the wrong address. Also, I’ve since made some slight changes to the circuit, but I was able to easily hack the board with a jumper wire to make it work.

Last night, I populated the board and wired up the pots, the switch and the jack. At this point it looks kind of like a mess of wires; this is my first circuit board design and I wasn’t too sure what was going on while I was doing it. Really all that matters is that I can fit the electronics into the cavity with no problems, and it does fit no prob. The next iteration will be much better, and for now, with 3 circuit boards running me about $7, I’m not sweating the costs or anything.

Next, I’m going to install a pickup I built a while back. I have some ceramic magnets on order from the fabricator, but they won’t ship until mid-October. Coupled with the fact that my original design used 16 small cylindrical magnets instead of 2 larger bar magnets, I’m going to have to make a few changes in my manufacturing process. In the end, I’m faced with a choice between installing the older neodymium magnet design today or waiting until mid-November for the newer ceramic design. The neodymium pickup sounds fine, but I prefer the character of the ceramic magnet design. I can just swap out the pickup when I finish with the improved design.