Ring modulation is achieved by inserting a 'modulation' signal into CV2 with both the CV2
and CV1/GAIN pots set to their maximum and in LIN mode. Auto-panning, whereby an input
signal is moved back and forth between the left and right of a stereo signal, can be done by
utilising both OUT A and OUT B. Set the CV1/GAIN pot to the middle position which allows
the input signal(s) to be heard from both OUT A and OUT B. Then by applying a control
voltage to CV2 you should find that the audio signal moves between OUT A and OUT B.
As soon as a jack is inserted into CV1 then the CV1/GAIN pot now changes from a manual
gain pot to a modulation depth control for the CV1 input socket. The pot now controls the
sensitivity of the CV1 input. The CV 1 input is a linear control input.
5V at CV1, with the CV1/GAIN pot set to maximum, will make the gain of the VCA
approximately 0dB or unity. Any CV higher than this will increase the gain proportionately.
However, it should be noted that the output signal level of the VCA cannot /-12.5V
or so. This upper output limit is restricted by the power supply rails of the modular system.
CV1, or the actions of the GAIN pot, and CV2 will act together too, so it is entirely possible
to get gains of higher than unity if both are set high enough.
The CV2 input
For CV2 two modes are provided, LIN and EXP:
The LIN input has a linear response. This means that doubling the CV will double the output
amplitude. In general this is the most useful response for general VCA duties. With the
CV/GAIN pot at its minimum, and the CV2 pot at its maximum, +5V at the CV2 input will
produce a gain of around one, ie. 0dB or unity gain.
The EXP input has an exponential response. This means that a rising CV will produce a
proportional change in gain measured in decibels. In practice this means that the output signal
appears not to quickly increase in level until the input CV is close to 5V. This effect tends to
produce wonderfully plucky sounds when used with a conventional ADSR as the CV source.
6
