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MOTM-300. The MOTM-300 Ultra Voltage-Controlled Oscillator sports a frequency range of 0.2 Hz to more than 38 kHz, and it exhibits better tracking and thermal stability than any other analog oscillator I have used. In typical Synthesis Technology fashion, this module includes a host of useful features without gimmicks. Each of the VCO’s four waveforms—sine, triangle, sawtooth, and pulse—has a dedicated output jack that can be used simultaneously with the others (see Fig. 3). The module also includes a 1V/octave input and two FM inputs. The first FM input has dedicated switches for exponential or linear FM tracking and AC or DC coupling. Control knobs are included for pulse width, pulse-width modulation (PWM) depth, coarse and fine tuning, and depth control for the FM inputs.

FIG. 3: Looking closer at the MOTM-300 front panel, you can see the 1/4-inch jacks conveniently placed at the bottoms (Click image for pop-up)

The MOTM-300’s sync feature is particularly interesting. The sync jack emits a pulse that can drive other VCOs. However, the jack can also accept an external sync signal, depending on the position of the Hard and Soft Sync switch. In Hard Sync, the sync jack acts as an input only. In Soft Sync, it acts as both an input and output simultaneously. The harmonic richness that results from Hard Sync, in which the pitches of the oscillators are locked together, is part of what gives an analog synth its characteristic sound. On the other hand, Soft Sync, a rare innovation that first appeared on the E-mu modular synth, latches two oscillators together when they are close in frequency but allows for drift when the frequencies are farther apart.

MOTM-320. The MOTM-320 Voltage-Controlled LFO has the same high stability as the VCO, as well as sine, triangle, ramp, and pulse outputs that you can use concurrently. The frequency range is from one cycle every 30 minutes to 2.8 kHz. Along with a 1V/octave input, the MOTM-320 has a Hard Sync input, an FM input, a rate control, an FM-scaling control, and a wave-shape control.
The MOTM-320 provides voltage-controllable waveshaping through the Shape input. This feature narrows or widens a pulse wave, makes a sine wave asymmetrical, or morphs a sawtooth from an upward ramp to a downward ramp. However, more sophisticated processing is also possible. For instance, to create syncopation in a particular piece, I synched the LFO to a clock and triggered an envelope generator from the LFO sawtooth. That turned the shape control into a continuous groove control that moved the trigger timing earlier or later in relation to the beat. To hear an example of this, visit

The MOTM system really shines when it comes to filtering. Each of the three filter modules sounds both stunning and unique. For signal processing alone, these filters might inspire an investment in a small MOTM system.


VCO Frequency Range

0.2 Hz-38kHz

LFO Frequency Range

1cycle/20 minutes-2.8 kHz

VCO Frequency Drift (24 hours)

<0.5 Hz

VCO Pitch Tracking Accuary

</=0.1% (25 Hz-3.2 kHz)

VCO/LFO Output Frequency Range

-5 to +5V peak-to-peak

CV Range

-7 to+7V

Gate Input Range

2.5-12V (positive)

Dynamic Range

>90 dB

S/N Ratio

>90 dB

Power Supply Voltage


VDC Power Consumption/Module

30 mA typical

Module Dimensions (single width)

8.75" (H) x1.75" (W)x5" (D)

MOTM-420. The MOTM-420 Voltage-Controlled Filter has a 12 dB/octave response and emulates the filter on a Korg MS-20 synthesizer. A switch selects among highpass, notch, and lowpass types of filters. The MOTM-420 has three audio inputs (each with its own level control), two scaleable FM inputs, and cutoff and resonance controls.

You can push the MOTM-420 into full resonance, causing it to cross-modulate with the incoming audio signals in fun and nasty ways. At maximum input levels, the filter sounds good and fat as it begins to distort. The 2-pole response lets some of the harmonics leak through, so the MOTM-420 tends to sound more open and cutting than the MOTM-440 filter.

MOTM-440. The MOTM-440 Discrete OTA Voltage-Controlled Lowpass Filter (with VC Resonance) has a 4-pole response that emulates the old SSM filter chips. Filters designed with SSM chips gave the Octave-Plateau Voyetra 8 and the Rev 1 and 2 versions of the Sequential Circuits Prophet-5 their thick, meaty sound. Those filters got their famous growl from subtle overmodulation within the filter itself, and the MOTM-440 manages to improve on that sound with a better signal-to-noise ratio.


Reprinted with permission from Magazine, March, 2001
2000, Intertec Publishing, A Primedia Company All Rights Reserved

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