This module is how we control volume in our modular system, and it works by multiplying different signals together (see video below). There are two complete voltage controlled amplifiers here, and an output that can mix (sum) them together. The jacks at the bottom of the module are the audio inputs, the jacks at the top are the audio outputs, and the topmost knobs act like you would expect a volume knob to (clockwise turns the volume up, counterclockwise turns it down).

What makes a voltage controlled amplifier special is what’s going on in the middle of the module. This is where we input control signals that can turn the volume up and down in ways that our fingers couldn’t do. The switches change how the module responds to a control voltage, and the knob above those inputs changes how much of an effect the control has.

Inspired by the MFOS dual VCA, built around an LM13700 OTA and featuring cv input attenuverter and output sum. Can be used as two separate VCAs or a voltage controlled mixer with switch between exponential and linear cv response.

See amplitude.

Low Frequency Oscillator with sine, saw, ramp, triangle, and square wave outputs. Switch between three frequency ranges and adjust with freq knob. LED flashes to indicate rate of square wave high and low. Frequency ranges from low audio to cycles lasting more than a minute. [For more information about how this module is used and fits into a modular system, check out the pages about amplitude and frequency].

Attack Decay Sustain Release (ADSR) are the 4 phases of this control voltage generator. Together they make variations of that mountainous shape that is cutting across the sliders. Why that shape? Well, it turns out that we can mimic a lot of different musical instruments by adjusting the length of each section, and applying the resulting voltage to the cv input of a voltage controlled amplifier or voltage controlled filter.

For instance, if we want to create a percussive sound we could apply the envelope to a VCA and make the attack (that first stage sloping up) very short, the decay (the second stage sloping down) a little longer, and the sustain and release unnoticeably short. To create a plucked string sound we could lengthen the sustain and release. For a bowed string we could lengthen the attack, and so on.

More information to come…

Dual four pole filter. High pass and low pass. More info to come.