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.

Since I already had a working schematic in Eagle, I eventually decided to design yet another version, this time with the modular synthesizer in mind. The result is 808K, a TR-808 kickdrum clone with the forementioned mods plus an Eurorack power connector.

Here's a recording of the module: