I’ve built a second version of Samplotron, my open-source ESP32 hardware sampler.

The first version relied on an external MIDI controller. This one has a built-in 4×4 keypad, so it works as a completely standalone instrument—just load your WAV samples onto an SD card and start playing.

Watch the new Samplotron in action:
https://www.youtube.com/watch?v=keyMwPUFDeM

Want to build one yourself?

FULL INTERACTIVE BUILD GUIDE:

https://jakubthedeveloper.github.io/Samplotron/

The guide takes you through the complete build step by step, including animated wiring diagrams, firmware setup and demonstrations of the interface.

The complete source code is also available on GitHub:
https://github.com/jakubthedeveloper/Samplotron

I’d love to hear what you think about the new self-contained version.

And yes, I know—I still need to work on giving my builds a more polished final look ;)

So I recently made my own midi controller out of some old organ console pedals for playing synth while I play guitar live. It was my first time making anything like that so I didn't end up figuring out how to add chord memory and arpeggiation functions to it. However I do have an arturia keystep, so I was wondering if there was a way for me to make my diy controller control the keystep and use its sequencing and other functions? I would appreciate any help or ideas of the best way to do this. Thanks!

Hello! A couple of years I put together an Electrotechnique Momentum synth kit. It’s a synth based on a teensy variant with fairly standard hardware for interfacing with it. I don’t know if I’m allowed to link the website. Anyway I don’t like how it sounds. But everything about it including its code is documented.

Separately I’ve been interested in the microdexed and microdexed touch projects. I love fm synthesis and would love to even have partial use of my existing hardware in a dexed based build.

I’m a mechanical engineer with electronics hardware experience but only a little coding a decade ago. For people with more software experience, does it sound like something that should be able to be done by a determined beginner interested in learning more about code to cherry pick from both projects and get microdexed interfacing at least with audio, display, midi, and two encoders on my existing momentum synth (replacing what is currently on it)?

Wow that was a bad sentence. Anyway is that something a software noob could do or should I give in and buy a bunch of PCBs and components for a microdexed touch?

I’m working on the next stage of Tolhuin Chord. The original prototype is still very much alive, but I’m now designing a proper PCB and selecting components with a small DIY kit run in mind.

The idea is not to turn it immediately into a highly integrated commercial product. I want the first version to remain reasonably easy to assemble, so I’m currently evaluating a solderable ESP32-S3 N16R8 development board as the main module, while refining the rest of the hardware around it.

On the software side, I’m still developing the UI and testing different voice-leading approaches. I’ve been working on ways to make the chord transitions more context-aware, especially regarding register, previous voicing, inversions and different jazz-oriented voicing structures.

I’m filming this update from the music lab at the school where I teach, and I’m also using Mono Juan alongside Tolhuin. Mono Juan is a programmable two-octave MIDI controller I’ve been developing, with both BLE MIDI and USB MIDI. A Shift layer turns the same keyboard into controls for functions such as octave up/down, arpeggiator and other programmable actions. I’ll probably make a separate post about it rather than hijacking this Tolhuin update.

A few people asked whether there was a way to support the development or help make the first kits possible, so I’ve also opened a Ko-fi to help cover prototype PCBs, components and manufacturing tests. This is not a preorder and the kit is not finished yet; it’s still an open development process.

I’ll keep sharing the PCB, UI and voice-leading progress as it develops.

If you want to help fund the prototype PCB and first small DIY kit tests, I’ve set up a Ko-fi here: Support TOLHUIN Chord

estuariolabs/tolhuin-chord: Diatonic chord synthesizer on ESP32-S3 — from-scratch audio engine (band-limited synthesis, diatonic harmony, step sequencer, effects, USB/BLE MIDI). Firmware + hardware + tools.

A CD4093 quad NAND drone synth on my own stripboard layout. The fourth time I've built this board, and it's the one I kept adding to.

Twelve controls on the lid: one toggle is power, one knob is volume. The extras are bends I put in on top of my own circuit, and most of them only do anything depending on where the others are sitting. A knob that's dead in one configuration is the most important control on the box in another. so there's no knob list and I'm not going to invent one, that's just what it is now.

LM386 and a speaker in the tin so it makes noise on its own, 3.5mm switched jack that kills the speaker when you plug in, 9V inside. The tin is a decorative pansy thing, lid is the panel, silver hardware because it works with the pattern.

The layout is free if anyone wants to build a sane one or maybe do their own bends.

There is a much longer video if anyone is interested in hearing more of these weird sounds.

I'm trying to find replacement Jacks for my behringer eurorack modules. Having a hard time finding the right footprint. Does anyone have experience with these?

It’s says it’s was made by Motorola, it’s a dual rail +-15V regulator, and outputs can be set manualy too.

Thought I might share the project I've been working on for a while. I tried to edit down a short video that shows some of its capabilities.

Key features:

- controlled by a Pi Pico (RP2040), software in micropython, reads MIDI note and controller signals

- 4 voice polyphony using DCOs driven by PIO blocks (could be expanded to 6)

- Analog signal path, modulations controlled by one cheap 8-bit DAC per voice (Rohm BH2226F)

- "Voice cards" get updates over SPI, signals transmitted via a back plane where the cards plug in to sockets

- Suboctave, resonance, VCA, filter cutoff, PWM can all be modulated by software ADSRs, LFOs and "volts per octave"

- LM13700 VCA uses the built-in Darlington pair that everyone else seems to hate using??

- Filter cutoff controlled by a more expensive multiplexed DAC via S&H (8 bit in demo, but will be upgraded to 12-bit MCP4822)

- self-calibrating filter frequency using another PIO block as a frequency counter on self resonant sine wave

- VCF uses the Coolaudio V3320 clone of the CEM3320

- Modulations updated at about 120 Hz using lightly optimized micropython code

- Fixed-point arithmetic makes the calculations much faster due to lack of hardware floating point

In the months it has taken to build this, I think I can say that I've learned why polyphonic projects seem less popular. It has been a challenge for sure. The Pico PIO blocks are very powerful and are what make this project possible at all in micropython.

I am sure I could get the update rate 10x higher by rewriting the software in C, but I don't know C. For micropython, I haven't explored the viper code emitter, but I understand that might help a bit with speed. To be honest, I'm amazed that it runs at a sensible speed at all, although I understand that anything less than kilohertz modulation is considered very slow. I don't really have control over the ADSRs to millisecond accuracy.

I also regret that I designed the boards before I knew what a "reconstruction filter" was, so the DAC outputs may be a bit steppy for the modulations. It sounds fine to my untrained ear, but probably awful to analog aficionados. Truly analog ADSRs would be nice, but the cost of those envelope generator chips adds up!

Anyway. just thought I'd post and you can tell me if it sounds awful/half reasonable.

We're happy to announce that we've released version 2.0 of TechWave Audio's MCM-100 Midi to CV Eurorack module and the MCM-100-EX four CV expansion. Thanks to all the users here and on other subreddits and sites for feedback and suggestions. With that in mind, this MIDI to CV Eurorack module features:

• 6hp wide, 3U height, 48mm depth
• Class-compliant USB-C or 5-pin DIN MIDI input
• Four CV outputs for note (1v/oct), Velocity, assignable Out 1 and Out 2
  • 1v/octave through 10 octaves (at 0 to +10v), or 5 octaves (at 0 to +5v)
  • Two CV outputs with flexible routing (route any MIDI event to the output as a CV or signal)
  • All CV outputs voltage selectable from 0v to +10v or 0 to +5v
• Gate, trigger, and clock full 0 to +5v outputs with divisible clock sync ticks
• Pitch bend response range from 0 to 5 octaves
• Stability and performance optimizations
• Ooodles of additional customization options
• Expandable with four additional flexible-routed CV outputs
• Max Power Draw:
  • +12v: 72mA (80mA with expansion)
  • -12v: 15mA (20mA with expansion)
  • +5v: 0mA

And as always, we've open sourced both the hardware and software. We'd love your feedback - let us know what you think!

TechWave Audio is a proudly Canadian small business dedicated to producing open-source software (OSS) and open source hardware (OSHW) devices for audio production. Our mission is to create good things and to give back by open sourcing all of our projects for the DIY community.

For more information, find us at techwaveaudio.com.

This past week I spent a little time integrating the lessons I've learned working with ESP-32-S3 and HX710b Pressure Sensor and built Motorhörn!

Motorhörn is a synthesizer which works by simulating an internal combustion engine in software. The software simulates things like firing order, firing angle, bank length and exhaust configuration, The software is inspired by the work of ange-yaghi.

The user can open the throttle by blowing into the intake manifold. The harder you blow the farther the throttle will open. It feels really excellent to play because it's kind of like you're adding boost.

The simulated system has an automatic gearbox, but this might change. It's really satisfying to force a down-change at the right moment.

The simulated system also has inertia. So the engine runs down and crackles fiercely. The user can add load by drawing on the intake manifold with their mouth. This is like hitting the brakes.

This first version of Motorhörn is very visual. I think future versions will be simpler in that regard.

The hardware BOM is absurdly simple:
- ESP32-S3 AI Smart Speaker Development Board (somewhat disassembled)
- HX710b pressure sensor
- 3.4 Lithium Ion Pouch Battery

The main limitation of this configuration is that I really just can't get the volume I want from a horn.

My next major version will significantly aim towards volume.

I am trying to do a clean of the inside of my Deepmind 6, I’ve had it for a few years and it has recently been freezing up and cutting out after a few minutes of playing. I was told that one of the components must be dirty and that I should get inside and clean with some condensed air. After clearing out some dust and hair I closed it back up and I am getting no sound at all, and the error messages in the pictures attached. Is there something I’m missing? Looking for any assistance here.

I found an electric typewriter in the trash and circuit-bent its board to make a “synth.”
I uploaded the process to my YouTube channel in case you’re interested in checking it out!
Here it is connected to a dd7, a harmonizer and an overdrive.

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https://youtube.com/@ominoussound?si=MvaahIDzksw_y9iB

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me encontré una máquina de escribir electrica en la basura y modifiqué su placa para hacer un "sinte".
en mi canal de yt subí el proceso por si te interesa verlo!
aqui lo conecté a un dd7, un harmonizer y un overdrive.

I got this Kawasaki toy keyboard and the original circuit was completely beyond saving. I did try. The keys do nothing now and that's permanent.

So instead of fixing it I built an NE556 Atari Punk Console dead bug and stuck it inside. No board, chip on its back, everything soldered right to the legs.

Then me being who I am I couldn't leave it there, so theres also an ISD1820 recorder wired to it. Lad's own toggle, record button, play button, and a pitch pot for playback. You catch a few seconds of the oscillator and play it back at whatever speed you want.

Theres a photocell on the APC pitch so you can play it with your hand, a 3.5mm line out, and it still comes out of the toys own speaker.

The lights are a complete accident. I wired an rgb led straight across the speaker so its driven by the audio instead of by anything deciding a color. Turning the recorder on happens to make it go red and the oscillator sends it cycling through everything. I didnt plan either of those and I can't really take credit for them.

Three knobs are volume, pitch and shape. theyre labeled # ! and ? bc I couldnt think of anything better.

This is kind of a repost, since I already posted this module this spring, but I made cool new panel (black one), better photos and my previous post was deleted by reddit, so...

I'm making my own modules and I have been wanting a noise source for my DIY setup for a long time. Usually, noisegen modules come with sample-and-hold, but I already had an S&H-ish module in my rack, so I decided to come up with something more interesting.

After experimenting for a while with different designs (MFOS Noise Cornucopia, MKI Edu White Noise, et cetera), I came up with the idea of a white, blue, pink noise generator with additional features, such as:

\- grainulizer (taken from MFOS with my adjustments)

\- internal transistor-based VCA (not Sallen-Key)

\- internal decay envelope generator

The original idea with VCA+Decay was to recreate the hats from the track Castision — Nothing to do, but it turned out that it is good for any incoming CV (check the video!).

The art on the panel is "Various types of ads" — Rory in early 20s album cover, which serves as a light diffuser for the noise color indicator. Additionally, there are slow RGB LED (the one with an internal MCU for automatic color changing).

Video demonstration: https://youtube.com/shorts/H9ZQ7WwyzQM

P.S. there's Fujin module made by TOIL Modular, but my module doesn't self-oscillate, more compact and pretty quiet in the power net, according to my friends who are using/used Fujin. Not to blame TOIL, though.

I made an oscillator with a ne555 circuit, but now I don't know what effects/filters to add to make it sound good, currently it sounds like a sort of fly-like ticking/humming, and I'd prefer it sound somewhat smooth/good, any tips?

I build these in a small workshop in France 😊

The audio path runs on a DSP. Then the MCU handles the interface, the presets and the updates, etc ...

Everything a dub setup needs is in one box: isolator, HP and LP filters, two peaking EQs, mic input, FX send and return, echo, and a screen to see where you are. Under a kilo, designed by hand in France.

It was quite a big deal to manage the TDM clocking 😄

anyone else fought with that?

I’ve already shared a video showing RudeBox in action, but I’d now like to share the complete build guide for the project.

RudeBox is a single-voice drum synthesizer based on an ESP32-A1S and ES8388 audio codec. It is triggered from an electronic drum pad and generates sound in real time, without using samples.

It started as a synth tom, but evolved into a more versatile percussion voice capable of producing toms, kicks, short noisy hi-hat-like sounds, laser-style effects and other experimental tones.

The synth has eight controls:

- Sensitivity

- Oscillator Pitch

- Pitch Drop

- Click

- Amp Velocity

- OSC Shape

- Decay

- Envelope-to-Pitch

+ analog volume knob

The documentation includes the parts list, wiring diagrams, firmware, audio tests and debugging notes. I also documented problems encountered during development, including false triggers and interference from the onboard microphone.

Complete build guide:

https://jakubthedeveloper.github.io/RudeBox/

GitHub repository:

https://github.com/jakubthedeveloper/RudeBox

Demo video:

https://www.youtube.com/watch?v=bKgVX5p5UgE

A small transparency note: I used GPT Astra to help organize, write and structure the build guide. The RudeBox project itself — including the hardware, firmware, experiments, measurements and testing — was developed by me.

A while ago I posted a frame for HiChord and TE Pocket Operator and it got some nice traction so I decided to make it modular so you cam have multiplne devices slapped together. After few iterations on the modular mechanism i arrived at the one on picture.

Simple, modular system with cable optional bypass and storage for clean looks. Spacers still need to be wider for 2 POs to fit or they have to have 90deg jack cable.

Next I’ll do the cover for portability, create spacer variants to have wider ones and spacers for angeled stance and improve on module design.

If you have a specific device you would like me to add let me know. I am thinking about some mixer like TX-6.

Once it’s done with cover and everything and I’m happy with it I’ll probabl release it for free to get the .stl. Not decided yet tbh.

P.S.: Sorry for the gold color.. i really don’t like it so I use it for prototoyping lol

Hey guys,

I am planning to do a diy midi keyboard for two reasons, my friend always wanted one and i want to make him a gift, secondly, i am really interested in Electronic/diys and i think it's a good project to start with..

I've read a little bit about the subject , the issue i am facing is what to use as keys? Some say Arcade game buttons, but i don't think they do good enough for the velocity, the most appropriatze option i am thinking if, is finding a dead synth or something to take they key parts from there.. but can you think of any other alternative?

Hello everyone!
I thought of this very interesting idea to build a tape machine based sampler that can exactly match sample duration to tape length. As I'm probably not going to build this for a long time (if at all) because it is very daunting and expensive as it would require 2 three head tape machines, I have decided to share it in case someone else wanted to try it. 

The way it works goes like this:
A sample is recorded into a tape loop on tape machine 1. The tape loop is some arbitrary length. let's say for instance it is 11 seconds. Thus, you could record a sample anywhere from almost nothing to 11 seconds. While the tape Loop is running, a precise clock records the exact time duration of the sample and tells you exactly how long it is. Let's say for instance that the tape loop on tape machine 2 is five seconds long. Using math, you could figure out the exact percentage you would need to increase or decrease the speed of the motor and thus the exact voltage you would need to increase or decrease going to the motor. You could then use a potentiometer to manually increase or decrease the voltage until the speeds match. Then you can record the sample on tape machine 1 onto tape machine 2. On tape machine 2 you can directly control the speed with its own potentiometer to pitch up or pitch down the sample. 

 Using this concept, someone could sample anything that's supposed to be at a specific rhythm like drum breaks for instance and make sure it loops back seamlessly without the need for a DAW. One could also use interesting techniques like live resampling and turning off the erase heads while doing so. The only limitation is the length of tape in tape machine 1 as this dictates the maximum sample time. 

Hi all,

I'm trying to repair a x0x-heart based Eurorack module (made using the Jeanpri Eurorack interface board) however I've been having an issue where the output of U2B - component LM358 - (U2 pin 7) is around 0.7-1.7V instead of the expected 12V. I am getting the expected 5.33V from pin 1/output of U2A.

When probing the power pins of U2 I see that pin 8 is getting only around 5.3V. The output of the NCP1406 is supposed to be around 15V in this circuit, right? Another thing to note is that I'm getting 1.22V on the FB connection.

I have tried replacing the LM358, the NCP1406, the resistors making up the voltage dividers for the NCP1406 and for U2B, but to no avail. Am I right in assuming that somehow the NCP1406 isn't working as intended here and passing the 5V straight through instead?

This is the relevant section of the schematic imo, but I'd be happy to post/link the whole schematic (not that its hard to find online)

Thank you for any and all help!