The ED104 comprises 2 LIN/LOG VCAs with additional VC Panning function.
In July 2002, EDN Network published an article by Mike Irwin on the application of op-amps to linearise the response of a voltage controlled attenuator built around the Analog Devices SSM2164.
In September 2003 Phillip Gallo published a design for a Dual LIN/LOG VCA utilizing this design idea and the ED104 realises that design in a euro-synth module.
Although the ED104 has two separate VCA’s, the [LIN/LOG] control law is switched simultaneously for both VCAs so that they both operate with the same control response.
In stand-alone mode a control voltage is fed in to [CV x] while an audio signal is fed in to [AUDIO IN x] with the resultant output at [AUDIO OUT x].
With the CV level control at maximum, a 0V to 5V signal will raise the gain of the VCA from -100dB of attenuation to 0dB while increasing the voltage from 5V to 10V will further increase the gain from 0dB to +20dB.
For operation in Panner mode, a single audio signal is fed in to [PAN AUDIO] while the panning control voltage is fed in to [PAN CV]. The [CV A] and [CV B] level pots should initially be set to maximum