I present: The Octodrōn
8 Super Simple Oscillators, now, how do I make it CV controllable?
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(It makes each oscillator considerably more complex, of course.)
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Hmmmmm. Best not fly before I can walk, I think I’ll just stick to twiddly knobs and making weewoo noises for now haha
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I approve 100% of the use of pink LEDs! I’ve built four EuroPi modules so far, each with a different LED colour - my most recent one is also pink LEDs…
Fresh off the printer is another 3D printed Eurorack case/frame. This is a 20HP desktop frame to hold bits together while I work on them.
Currently in it is the pink LED EuroPi (as mentioned in the previous post) and a simple attenuator. In the middle is a module I’m working on called “um, what?”
I built it for trying out the features in CircuitPython’s
synthio module, which is getting a lot of development time spent on it at the moment. Inside there’s a Seeed XIAO RP2040 board with an I2S audio board, Eurorack level shifter and Hagiwo-inspired protection to the analogue inputs used for the CV jacks. Built, like many of my things, on an @analogoutput protoboard (thanks so much for sharing that design Rich). Work in progress shot:
Up front there’s two pots, two CV inputs and a rotary encoder. The code running on it is a generative drone using the CV input as a base for cycling through saw, square and sine waves. It sounds so much better than I expected (which is why I built a module around it).
My plan is for it to be a simple wavetable synth, using the legendary AKWF Waveforms as a basis.
Oh, and I made a super sketchy USB audio interface by butchering a £1.80 USB audio dongle. ‘Out’ gets attenuated and pushed into the microphone input, and then I can plug in a USB C cable to my PC or MPC.
It works ¯\_(ツ)_/¯
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Looks good, what printer are you using? My Ender 3 never prints anything right anymore 
It’s a heavily modified Ender 3 Pro. I’ve swapped the print surface, replaced the shroud around the hotend and changed all the fans with silent/more efficient ones, added a levelling probe and got a dual Z-axis setup to prevent any sagging possibilities. It’s been an excellent work horse and I feel guilty for lusting after Bambu Labs P1Ps in front of it!
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Print quality is really a question of tuning more than anything. A Prusa will print right out of the box and won’t need frequent maintenance, a Voron can be pushed to print much faster, but a well-tuned, maintained and upgraded Ender 3 can still reach the same level of print quality. It’s what I use too.
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I noticed with mine that I was having problems with adhering the build to the plate. Putting down a layer of painters tape cleared it up. Works like a charm every time I print now.
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Have you tried a thin layer of pritt stick to help with adhesion
the prints usually start off fine, then turn to string… it was fine for the first 18 months ( bought in Lockdown #1 ) . I need to actually test it again as i have not done so in a few months, just my son says its still poorly… It did some great stuff early on.
Looks super cool! What power supply do you use?
This armature is just my test rig, so it’s using a bench PSU. I have yet to build my real first case with a proper PSU
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“How many channels you want in your mixer?” “Yes.”
Well, this 6 mono + 2 stereo (line or modular level) input mixer works, but I AGAIN wired mono volume pots backwards. Well, I need to do a bit of a redesign on the mainboard too, the power connector was partly under the jackboard as well as the power input capacitors.
And maybe I could fit a clip indicator led there too, the main board is getting a bit crowded as all the components are on the same board with the potentiometers and the jacks take about one third of the space. And there’s 4 TL074:s there. Lot’s of traces going to a small section of the board like this:
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I designed and mostly built this overly complicated wavefolder last August, but I was missing two AS3360:s, so it was left unfinished. Then I started to have a bit of a dread to finish this as it would be horrible to debug if it doesn’t work at all, but I remembered that I had two of those chips now, so I put them in and for a very big surprise, this worked.
Well, mostly worked, I noticed couple of problems that should be solved with testing different component values, and one resistor is just wrong, resulting way too much gain. And yeah, this is Eurorack for a change.
Oh, and the hidden controls are “input filter”, “gain”, “offset”, “fundamental”, “distortion”, “output filter”.
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Helloooo, this is my kinda module. Can we get a sound demo?
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Here’s something random from my first test: krakenpine.kapsi.fi/other/wavefolder-random-test1.mp3
It’s just a sine wave with me messing with the controls and couple of envelopes and a lfo going to CV-inputs randomly. In the end there’s a bit with saw wave in the input so I could test how the input filter makes that kind of waves play nicer with the wavefolding.
The gain, offset and distortion can all be used as very odd VCA:s as in the extremes they can cut the signal of completely. Or technically “offset” doesn’t have CV, that input is just whatever mixed with the original input signal after first “gain” stage, so you could say that this is a mixer too. LFO or envelope is basically just offset voltage in that context.
I only needed to change three to get gains better and remove unwanted distortion, but I think I want to desolder few other resistors and put sockets for them to test few better values. This could sound even weirder.
This is probably the most Buchla-esque thing I’ve designed.
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ShedSynth DELAY module similar to LMNC single delay (thanks Sam), squeezed into Eurorack 4HP on perfboard.
Wot no knobs? It doesn’t have the usual controls for dry/wet mix and repeat, other modules get that job.
Wot no CV? Breakout pins on the back to experiment/plagiarize without having to breadboard the whole circuit again.
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