Teenage Engineering OP-Z to DJ Controller adapter

I started getting interested in DJing, but didn't want to invest into a proper controller right away, so I looked for something that I already own and could be (at least) temporarily repurposed to be able to experiment with. I realized that the OP-Z already had infinite encoders, which are kind of suitable for this purpose, but there were two issues:

• They are too small to be directly usable
• Their resolution is too low (about 32 ticks per revolution compared to the hundreds on entry level and even thousands on professional desks)

In order to overcome these limitations I decided to try and somehow upsize the rotating part, but instead of directly attaching it on top of the encoder I aimed for having some kind of a belt drive system, which would also allow for the introduction of a rotational multiplication factor, thus increasing the effective resolution. 

In order to avoid wasting filament I looked for something round and thin and what gives, a CD happens to fit this description very well. 💿 (In case you're curious, all this time I've been setting the imaginary dance floor on 🔥 with various hits from an old Ubuntu 11.04 Natty Narwhal Alpha 3 installer. 😃) 

To assemble the contraption, you'll also need a bearing with a 22 mm outer diameter and an 8 mm internal diameter, the same dimensions as those included for the Prusa Mini spool holder. In case you don't have those, a 20 pack of 608-ZZs can be had for less than €10. You'll also need a few LEGO Technic Axle Rods, but if you don't have them on hand, I'm fairly certain that many suitable alternatives can be found that you can print as well.

---

P.S. Source code for the MIXXX controller mapping and script is attached in the “Other files” section, I will try to clean it up and submit it as a contribution to be included in later releases. The current version assumes that the “module” track (#13) is selected, but you can override the MIDI values as you see fit.