Here are two DIY or build them yourself modules for Eurorack. first up is the Tabula Rasa an Arduino based wavetable oscillator that lets you create new waveforms, dump them to SD card and use them in your Eurorack modular. Then we have the Spring reverb from Music Thing which is a voltage controlled spring reverb hooked to a real spring tai. it also has the option of being built with a digital brick reverb tank as well.