Multiplier

1FW Polarizing VCA aka RingMod

The Multiplier module is a Polarizing VCA (4-quadrant multiplier) based around the precision AD633 Analog Multiplier chip. The difference from a regular VCA is that negative voltages will invert the phase of the output – so you can use it, for example, to modulate a saw into a ramp.

The main input is multiplied by a summation of the Intial control along with two Modulation inputs with depth controls & invert/mute switches. The Initial control goes from 0V to +5V with the switch set to +, giving an amplification range of 0 to +1, and from 0 to -5V with the switch set to -, giving an amplification range of 0 to -1. When set to the centre switch position the Initial control has no effect.

For the modulation inputs, be aware if the modulating signal is bipolar (+/-5V) or unipolar (0 to +10V). With Initial set to Off, a bipolar input turned up full will swing the output from -1 through to +1 amplification, whereas a unipolar input would swing the output from 0 to +2 amplification. Set modulation depths accordingly and/or use the Initial control to offset the amplification range.

Traditional Ring Modulation is achieved with the Initial Control set to Off and full modulation from a bipolar signal – but with the Initial control and the 2nd Modulation input you can stray a long way into more esoteric areas.

The module is DC coupled but the main input can be AC coupled if required via a rear jumper.