Music and Synth DIY

Eurorack, Synth DIY, Through hole

Prototype keypad utility for TAPLFO3 LFO

This is a prototype for a very simple utility keypad module to control the waveform select, Waveform bank, and clock multiplier parameters of my VCDLFO Eurorack module (based on Electric Druid’s TAPLFO3 chip & schematic).

The TAPLFO3 switches between different waveforms and clock divisions based on a voltage from 0-5v, scaled to +/-5v for Eurorack control voltages.Usually this is done with a voltage divider pot, or a multi-pole switch with different voltage divisions. This keypad uses an arduino with filtered PWM to produce this scaled +/-5v, latched with each keypress.

The finished module will have two latched +/-5v outputs plus a toggled 0/5v for the Waveform bank parameter.

This makes it possible to “play” the LFO live. It could also be configured to output appropriate control voltages for any other module with bipolar Eurorack CV input, by an easy modification of the Arduino code.

Here, it is connected to the Clock Multiplier CV input of the LFO, and is switching between clock division multiples of a (tempo clocked) LFO. In turn the LFO modulates the cutoff frequency of a filter, for some cheesy wobble bass as an example of a use.

I’ll upload the build files once I complete the PCBs and test them.

VCDLFO module:

Electric Druid TAPLFO3:…