A dual linear voltage controlled amplifier/attenuator now in 2HP, based on the LM31700 chip.
Our re-vamped dual linear VCA. Version 2 is similar to version 1 with some improvements in quality and response and has also been fit into 2HP. The unit is pre-offset to be normally closed, a positive voltage applied to the CV input will amplify any AC or DC signal present at the input, with +5V giving unity gain. It will accept voltages of up to 10V amplifying the signal up to 200%.
Also new to version 2 are the inverted CV inputs. These invert any CV and sum it with the non-inverted CV input. For example inputting a positive voltage at CV INV will have no effect on the VCA if it is currently closed but if there is a voltage at the CV input acting to amplify the signal, then a positive voltage at CV INV can be thought of as a secondary subtracting or ducking control.
Furthermore a jumper on the board allows you to set ‘auto-offset’ to the CV INV control (a single jumper affects both gates). When the unit is set up like this, inserting a jack into CV INV (even with no signal) automatically applies a +5V offset to the VCA, opening it up at unity gain. Any voltage at CV or CV INV will now amplify or duck the signal from this unity gain position. This is useful for ducking a signal that already has dynamics e.g from a synth voice or the wet output from a reverb/delay unit.