Developer Eric Archer is now shipping his Andromeda MK-1 and MK-2 drum machines, DIY minimal drum machines “designed as an experiment of making the most minimal drum machine possible using analog circuitry”.

In the video above, Archer demonstrates the two new drum machines, how they can interact and how you can control them in real time.

The Andromeda MK-1 and MK-2 drum machines are available for $55 each as DIY kits.

Here’s another demo. This one features 12 of Archer’s tiny drum machines:

The Andromeda MK-1 analog drum machine has a minimal sequencer with sixteen preset patterns, selectable by the red switch block.  The pushbutton restarts the patterns.  This feature allows you to shift the timing of the rhythm when synchronized with other Andromeda Space Rockers instruments.

The sound of the MK-1 is from a pair of damped sine wave oscillators, which are triggered simultaneously.  The oscillators are reffered to as “X” and “Y”.  Their pitch is controlled by the photocells AND the capacitors labeled X1,X2 and Y1,Y2.  The capacitors control the overall range of pitches that it can play.  Larger value capacitors here make lower pitches.

The square grid of holes is called the Personality Center.  You can use it to add additonal circuitry to your MK-1 to change its character.  I will publish the Personality Center mods as soon as I get a chance.

The Andromeda MK2 analog drum machine has a minimal sequencer with sixteen preset patterns, selectable by the red switch block.  The pushbutton restarts the patterns.  This feature allows you to shift the timing of the rhythm when synchronized with other Andromeda Space Rockers instruments.

The sound of the MK2 is from an analog white noise generator.  This noise is filtered by a resonant filter, and the cutoff of the filter is controlled by the photocell on the left side of the unit.

The sequencer triggers an envelope generator (EG).  This creates a signal that controls the duration and volume contour of the sound.  The EG is controlled by the photocell on the right side of the unit.

The EG’s signal is sent to a voltage controlled amplifier (VCA).  The VCA chops up the steady output from the filtered white noise generator into little bursts of sound, controlled by the EG.  This is what you hear at the output.

The sound of the Andromeda MK2 is like a primitive electronic snare drum / cymbal / handclap.