Hi, I’m new to DIY synth projects (new to truly DIY that is, I’ve built a few kits before) and I have a project idea I’m excited about, but I’m not sure if it’s too ambitious.
I found a schematic and parts list for a DIY Mutron Octave Divider clone, and my thought is that if I can recreate the schematic in a CAD program, make a few adjustments, and design a PCB from there, I’d be able to make it into a eurorack module.
This one maybe?
It’s a bit more complicated, higher part count than my first. When I started using KiCad I went through a video tutorial and followed along to create a really simple LED flasher PCB (and got it fabricated). I had an original module idea or two in mind but decided for my first “real” project it’d make more sense to do something based on a known good, and not too complex, circuit. So I went on to draw up a PCB for a Music From Outer Space VCF. Two chips, three transistors, a couple dozen passives. Aside from getting some of the pot connectors backwards it worked (not that I wouldn’t do some other things differently now). Getting everything right the first time is not to be expected!
The octave divider might make a better second or third project — but I don’t think you’d be hopelessly over your head if you were determined to make it your first. Do take some time to learn about KiCad or whatever software you choose, though. Run through a tutorial and at least draw up some simpler designs first. And ask questions here.
(As for the octave divider — for a synth signal, where you’re dealing with simpler waveforms than with a guitar, there are much more simple circuits for octave division. This one for example.. But maybe the Mutron clone has some features that one doesn’t?)
I have a few PCBs under my belt, and a pair of PCB-based Eurorack modules based on other people’s circuit I’m currently trying to debug. All made using KiCad and printed by JLC.
I went to look for the schematic (and if i had waited 5 minutes more before posting I could just have spared me the trouble to search and used Rich’s link lol)
A bit scary! I wouldn’t trust myself to get something this complex to work on the first attempt, especially as it’s a guitar pedal expecting different voltages than Eurorack.
But really, the question is, what skills do you bring to the table? A few things to consider:
Aside from the voltage converter which you probably wouldn’t use in a synth module anyway, all I see there are op amps (RC4558 in the kit, which seems to be readily available, but I have little doubt you could replace with TL072 with no problem anyway), a couple 4000 logic chips, and a bunch of passives. So parts availability doesn’t look like an issue. (Nor is EDA symbols and footprints, I’d’ think.)
Speaking of op amp replacement, I’d definitely recommend breadboarding before going ahead with a PCB.
As for the voltages, at least this design uses a dual supply, so there’s none of that fake ground business to deal with. ±9 V, it might just work with ±12 V, or if all else failed you could regulate ±12 V to ±9 V.
But a thing to contend with is that this is designed for a guitar signal, presumably expecting and producing lower signal levels than synth; you’d need to address that. You could build in the CGS Stomp Box Adapter circuit. Something else to breadboard.
I just noticed there are clear pictures of both sides of the PCB in the assembly instructions, with big fat traces pretty easy to follow. Laying out a duplicate design would be pretty brain dead. Of course you don’t want a duplicate, you want a synth module version, but the pictures might help.
your 1st design does not even have be anything.
It was by no way my 1st design, but I created a pcb anoit 1x1 inch with some random tracks, holes, graphcis… Served no purpose but was actualy just a key fob tab. But for a few quid it gets you thinking about the end to end process with KiCad and JLC with no stresss of it being electronicaly wrong.
My first actual PCB back in 2020 was a tiktok clock clone , mechanicaly it was faulty, it had a missing track and was generaly poor , but I learend a lot from that simple layout. I never actualy revisited the cloc to make it a module.