zetaSID

A compact SID voice with big retro character, the zetaSID brings classic C64-style timbres into a 4 HP Eurorack format. It is a monophonic digital module built around the MIDIbox SID synthesis engine, with CV/gate control and DIN MIDI in for flexible integration in modular or MIDI-based setups.

What makes it stand out is its expandable phybus architecture: multiple units can be linked for stereo operation, polyphonic setups, or even detuned unison stacks. The engine is deep, with six LFOs, dual envelopes, quad wave sequencers, eight modulation paths, and an extensive trigger matrix, while firmware 1.5 adds a bassline engine and three CV input sockets for more hands-on control.

It’s also a DIY, open-source project that’s still in production, making it especially appealing to builders who want a compact but ambitious digital voice with a vintage SID personality and plenty of room to grow.