Sub-Octave Multiplexer

The MOTM-120 is a Synthesis Technology exclusive design. Based on an article in Electronotes, we have updated, improved, and added features to create a truly unique module.

The MOTM-120 contains two 4-stage sub-octave dividers, a digital multiplexer, and four digital ring modulators. It operates in one of two modes, selected by the Mode switch.

In the simplest operation (Mode switch set to Sub), a single input is fed into the A In jack. The signal passes through a level comparator, whose lower threshold is 80mv peak-to-peak. When the input exceeds this, a 4-bit binary counter is clocked with the input signal. This generates the lower four sub-octaves. These are then mixed by 4 individual pots along with the input signal. A switch selects either the original source mixed in or the "squared" version of the input.

The additional four sub-octaves (similar to pulling out lower octave drawbars on a Hammond) greatly fatten up the bottom end of any signal. Even a simple sine or triangle will punch through the mix.

Lots of synths have a single sub-octave, but the MOTM-120 gives you four!

But the real fun starts when you flip the Mode switch to Cross. In this mode, 2 input signals are required. Each is divided into their respective 4 sub-octaves, then each sub-octave is ring modulated with each other! Since we are in the digital domain, it's easy to ring modulate. This results are simply awesome and bizarre. If A In is audio, but B In is from a LFO, what you hear is a 16-cycle pattern of the suboctaves being multiplexed. As the B In signal is raised into audio frequencies, the results are HUGE chordal timbres with lively beat frequencies. Electronotes used to describe this as "waveform animation," and that's a pretty accurate description.

The MOTM-120 is a powerful addition to your studio. The wimpiest digital synth can be turned into a growling monster!