The MOTM-110 is a combination low-noise Voltage Controlled Amplifier (VCA) and Ring Modulator (also called a "Balanced Modulator").

Voltage Controlled Amplifier

A VCA is an amplifier whose gain (output voltage) depends on a control voltage. The MOTM-110 uses the industry standard of 0 volts for no output and +5 volts for maximum output. The VCA is linear, meaning half gain is +2.5V, quarter gain is at +1.25V, etc. This is the most common form of VCA, since the driving control voltage is usually the output of an Envelope Generator (EG), whose output is not linear, but exponential. Why does this matter? Because of the way the ear/brain works, to get linear volume response requires an exponential amplifier response. So, we use easier to build linear VCAs and exponential EGs.

VCAs are also used to add tremolo effects, using a Low-Frequency Oscillator (LFO).

Normally, a VCA is designed for unity gain: a +5V control voltage means the input signal is simply "passed through". So, to be 100% accurate, most VCAs are really "Voltage Controlled Attenuators". But since this is a MOTM design, why be content with that? The MOTM-110 has a unique GAIN function: the initial gain of the VCA can be set from 0 to 1. If the gain is initially 1, then the output is 'on' all the time and INCREASES as the CV increases. This is useful if you have negative-going envelopes: you can get the "play the record backwards" effect. Also, the initial gain can be set so that the input CV is 'buried': at +5V the gain is less than 1. Again, interesting "clipped" tremolo effects can be achieved with proper GAIN pot settings.

Ring Modulator

The MOTM-110 has a 'true' 4-quadrant analog multiplier for it's ring modulator. This is a very low-noise design, using CD-quality opamps and a special patented Gilbert multiplier chip. Electronically, what a ring modulator does is take 2 input signals and multiply them together. This creates additional spectra which are the sum and difference frequencies of the 2 inputs. For example, if you fed in 2 sine waves, 1 at 100Hz and 1 at 150Hz, the output would contain 250Hz (the sum) and 50Hz (the difference). Big deal! What does it sound like?

The answer is this: metallic, clanging, noisy, and industrial! The reason is that these new sum & difference frequencies are not harmonically related in a musical sense (at least a Western 12-tone scale sense!). If you want wild distortion, robotic, or metallic sounds, you NEED a MOTM-110!