Synthesis Technology MOTM-120 Sub-Octave Multiplexer


  • A In
    controls the volume of input A
  • B In
    controls the volume of input B
  • Sub 1
    controls the volume of sub-octave 1
  • Sub 2
    controls the volume of sub-octave 2
  • Sub 3
    controls the volume of sub-octave 3
  • Sub 4
    controls the volume of sub-octave 4
  • Input (Norm/Square)
    selects either the original source mixed in or the "squared" version of the input.
  • Input (Norm/Square)
    selects either the original source mixed in or the "squared" version of the input.
  • Mode (Sub/Cross)
    switches between the sub-octave and ring modulation functions


  • A In
  • B In
  • Output


Synthesis Technology

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 2 4-stage sub-octave dividers, a digital mux, and 4 digital ring modulators. It operates in one of two modes, selected by the cleverly named MODE switch.

In the simplest operation (MODE is 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 pk-pk. When the input exceeds this, a 4-bit binary counter is clocked with the input signal. This generates the lower 4 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 4 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 in the mix.

Lots of synths have a single sub-octave, but we give 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 (you'll have to buy one to see how we did it!). 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 patteren of the sub-octaves getting multiplexed in. 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!

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