LEET is my vision of a new kind of modular affordable synth you can build yourself. It consists of several MIDI devices that can be used together or separate with your preferred DAW.
It became a massive project covering industrial design, embedded programming, 3D modelling, electronics and music theory. I’m happy with the current state, but I hope that with the help of others, the project will continue to evolve and improve.
I have designed a keyboard, drum pad, chord keyboard, control unit, arpeggiator and a step sequencer. One special feature is that the units have RGB LEDs for each key, enabling playback visualization (so each device is both MIDI out and in). This is helpful for music training and editing, but it also looks great. They can be used as input devices to any computer with a DAW (Digital Audio Workstation) like Ableton, Logic, Cubase, Garageband etc. It will run on Windows, Mac or Linux (including Raspberry Pi). They can even be connected to your mobile phone (Android or iOS), providing a tactile super portable music development platform.
Build your own synth
The devices are easy to build and anyone with a 3D printer and basic soldering skills should be able to replicate them. They are designed to use few components that are easily accessible and affordable (one keyboard cost around $6).
Hacking is encouraged
Everything is open source and built with the easy to use Arduino framework so it can be tweaked, improved and complemented with new functions to fit all kinds of different needs. Build a wooden stand, add a light sensor to control timbre, connect it to a speak and spell or build something completely new – the possibilities are endless!
3D Printed Circuit Board
All devices are built around a 3D printed core (3DPCB) that creates the exterior of the product, holds all components in place and has integrated wire channels that connects the components in a fool proof way. 3DPCB makes the devices easier to replicate, less expensive and you don’t need to wait for PCB delivery.
I designed the devices to be simplistic, solid and playful. The design might be called retrofuturism since they are inspired by old-school mainframe computers from the 70s with lots of blinkenlights like PDP-10, but the addition of full color LEDs and 3DPCBs makes them futuristic at the same time (maybe they are from a past that never happened ;)
I kept the form factor for each unit similar and designed a simple snap on stand where two or three units can be stacked and tilted for easy access. The units can also be equipped with magnets, allowing them to be snapped together side by side. With this approach, a two or three octave keyboard can be constructed by joining modules next to each other.
There is also a snap on accessory that just contains a sticker in order to identify the units. Like “Lead, ch2” or “Drums, ch7”.
This project started as an idea to develop a synth using the 3DPCB idea. I initially planned to design a self-contained synth with batteries, sound generation and built-in speaker, but quickly realized that it would be more useful to build a modular system instead. By using MIDI, the project becomes flexible and enable high quality sound generation. I considered using MIDI over Bluetooth, but the increased complexity with batteries, charging circuits, size, cost and reliability, made me stick with traditional USB connections.
Before I started, I defined some goals for the project – this is what I aimed for:
- Easy to replicate
- Lots of blinkenlights
To demonstrate the abilities, I decided to develop different parts that are needed for a system that can record and playback a song with a keyboard, arpeggiator and a basic sequencer.
To me this is a proof of concept – see it as a base for inspiration. The input units/ keyboards are working great, but the more complicated sequencer has room for improvements. I hope that others will assist on development and that future firmware releases will improve the functionality.
What I really like with the project is how easy it is to build something unique. Combining the components (microprocessor, LEDs and switches) is like building with LEGO. It would take me less than a day to build a working keyboard that starts with the note “A” instead of “C” (if I for some reason would want one). Adding a gamepad joystick, or even a light sensor to control pitch bend, is just as easy. Sure, you need to have basic understanding of electronics, 3D modelling and Arduino programming, but it’s not that complicated, and a project like this is a great learning experience.
Can anyone build one?
If you can hold a soldering iron in the right end you should be fine. My 12-year-old have built a keyboard that works great.
What equipment is needed?
You need a 3D printer (fff/ fdm) with a spool of PLA plastic, a soldering station with a narrow tip (and preferably a smoke extractor) and basic tools like pliers. If you don’t have this at home visit your local hackerspace!
What does it cost?
The components for keyboard costs around $6 (depending on shipping and supplier). Prices from eBay:
* Arduino pro micro ($4),
* 13 LEDs from a ws2812 led strip (60led/m) ($1.1),
* 15 6×6 tact switches ($0.2),
* 34g PLA filament ($0.7).
The more expensive sequencer also needs
* 2pcs of 8×8 ws2812 LED matrixes (2*$8) and
* a micro SD card reader ($3)
How long does it take to build one?
Printing time for a keyboard is 3.5h on a Prusa i3 and soldering takes 1-2 hours, depending on your experience.
What is generating the sound?
A computer or mobile phone generates the sounds mapped to different channels. Sunvox is a great free option, but DAWs like Ableton Live, Logic Pro, Pro Tools, FL Studio, Cubase, Studio one, Reason, Garageband can be used.
The keyboards and sequencers are only sending MIDI commands (like note C3 on channel 4 at full velocity). This gives you full freedom to choose from east coast (subtractive), west coast (additive), FM, samples, wavetable, vector, granular or any other synthesis of choice. With a MIDI to CV interface they can control analog modular systems. Maybe I should design a eurorack version one day?..
Is the keyboard velocity sensitive?
No, the standard tact switches used does not provide any velocity or after-touch data. Using two switches per key and measure time difference can be done, but not something I have investigated.
How big is it?
The dimensions of a keyboard unit are 154x45x8mm (6×1.8×0.3 inches) (without cables and knobs)
This is a great project – how can I help?
I appreciate all feedback and ideas for future devices and improvements.
It would be super cool to develop a simple Android or PC application that maps soundfonts/ samples to different MIDI channels and automatically echo MIDI commands to enable LED feedback. If you are good at embedded development, the sequencer has room for improvements.
I created a forum where people who want to contribute can share ideas and assist with development: https://vonkonow.com/wordpress/forums/forum/leet-synthesizer-development/
What does it take to modify or hack one?
Most important is a “how hard can it be?“ mentality. Modifying it is a great way to understand how it works and learn new things. When you are done you will know more about electronics, 3D CAD and embedded programming. Don’t forget to post your hacks!
Do you have any ideas for future improvements?
Yes, lots of them, here are some:
* A playback device (Raspberry Pi zero?) that generates sound without the need for mouse, keyboard or monitor. (MIDI in -> audio out). Maybe something like this:
* A keyboard with mechanical linear switches (Gateron/ Kailh/ Cherry MX)
* A keyboard covering two octaves
* A keyboard with a small MIDI sampler and transposable playback.
* A tiny sequencer with 0.96” OLED display(s) instead of LED matrix.
* A full color MIDI visualizer using the sequencer display.
* An AI based deep learning synth using google magenta and ESP32…
Build your own
Below are links to posts for each of the different LEET Devices. All of them with BOM, building instructions and code + 3D models needed to replicate them.