TAG: eurorack

More than one year ago I decided to build a TR-808 kickdrum clone using Eric Archer's build documentation, and the first version I put together was done on a perfboard. It took quite a while, but thanks to a wiring pen and some patience, it was finally working.
While building this version, I also found a couple of interesting mods: a decay range extension and a "pitch" pot, which I decided to integrate into the prototype.

After some months, I started experimenting with Eagle, and created the first prototype of a PCB. Back then I didn't have a modular synthesizer (lucky times!), so I ended up using an Arduino together with an optocoupler to trigger the kickdrum via MIDI: it worked quite well, and I've been using it for a while, until I started building my first Eurorack modules.

Synapse is a simple, diy-friendly Arduino shield that will allow you to expand your modular synthesizer in new and creative ways. Here's the hardware features:

• 2 x control voltage inputs, 0 to 5V with diode protection
• 2 x control voltage outputs, individually configurable as 0 to 10V or -5 to 5V via software, with 12bit of resolution
• 2 x gate inputs
• 2 x gate outputs
• 1 x eurorack power connector (10 pin)

Please refer to the github repository for the latest version of the schematic, the BOM and the library. Please note that for the time being I'm not selling kits or pcbs, you'll have to order the pcbs yourself and source all the parts (see the links and infos below).

Throb is a free and open-source JUCE based plugin that generates clock/reset signals synchronised with the host tempo. It is currently available for Windows (VST2 and VST3, 32/64 bit) and OS X (VST2, VST3 and AU 32/64 bit).
The user interface is pretty simple: a knob to set the multiplier and three radio buttons to configure the clock resolution.
The multiplier is an automation parameter and therefore can be controlled using the respective host functionality. Both the multiplier and the resolution (ppqn) settings are serialized to the preset chunk.
You won't need a DC coupled audio interface, but please avoid sending the output of the plugin directly to your speakers/headphones.

When Ableton published the Link source code, I started experimenting with it and decided to explore the feasibility of a hardware Link-to-clock converter.
I made the first attempt with a Teensy 3.2 board and a a WIZ820io ethernet module, but due to some of the dependencies of Ableton Link, this approach proved too complex, as it would have required a complete rewrite of the low-level networking functionality.
Having abandoned the "bare metal" approach, the next natural candidate became a Raspberry Pi board: I had a Zero lying around and decided to use it to build the first prototype, mainly because of the power requirements and the form factor.

A couple of weekends later I had a working prototype and decided to design and order a PCB, which I only received almost two months later (thanks, Custom Office...). When the PCB finally arrived, I put everything together and spent some more time fine-tuning and optimizing here and there.
The final result is a hardware shield for the Raspberry Pi Zero board and the necessary software and scripts running on the Zero itself and providing real-time conversion from Ableton Link to eurorack-friendly clock and reset signals.