VM912 Envelope Follower cv-processors

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The VM912 Envelope Follower outputs a dynamically changing voltage that follows the amplitude of an incoming signal, either from within Voltage Modular, or from an external audio source, via Voltage Modular's sidechain in and IO Panel Audio Sources jacks. (See Audio Sources in the IO Panel section of the Voltage Modular user guide for more information about using sidechain inputs).

This is a great tool for creating dynamic CV signals that can be used to modulate just about anything in Voltage Modular. A drum loop, for example, could be used to modulate the cutoff frequency of a filter, the pitch or pulse-width of an oscillator, etc.

Input, Output, and Controls

Response Time- Sets how fast the follower circuit responds to incoming signals, from 0.01 to 0.1 seconds. Low-frequency input signals generally require the longer response times and vice-versa with high-frequency input signals. 

Threshold- Adjusts the voltage level necessary to output a 5V gate signal at the Gate Out jack.

Signal Input jack- Input jack for the AC audio signal that will be converted to a CV output.

Control Output- Output for the dynamically changing DC voltage derived from the input signal.

Of note is that the original 912 envelope follower is unique among all other envelope followers in that the output is in dB, which is essentially the log of the amplitude instead of the amplitude itself. This is huge, as in really huge. In all other envelope followers, the output is linearly proportional to amplitude, but that’s not how the human ear perceives sound, hence the superiority of the 912 design. It should go without saying that the VM912 module accurately recreates the response of the original.

Control Input- This input expects a positive control signal similar to what is output by the follower. It is then sent to a voltage comparator which compares this signal with the Threshold setting. If the signal is greater than the Threshold, 5V is output at the Gate Output jack. A slight amount of hysteresis is applied to keep the Gate Output from chattering. A useful application for this section alone might be the deriving of a gate signal from an LFO anywhere in its phase, or anything else a voltage comparator might be useful for.

If nothing is plugged into the Control Input jack, the Control Output signal is normalled, as indicated by the dotted line. This allows one signal to provide a dynamically changing DC voltage at the Control Output jack, as well as a +5V gate signal at the Gate Output jack.