Voltage controlled mixer VCA-II. www.haraldswerk.de

Motivation

This is another take on my voltage controlled mixer VCA from 2021. The functionality is the same. I changed the function of the sliders and the pots though. Now the sliders are controlling the mix and the potentiometers controls the amount of the control voltage. The jacks are moved to the top. Those changes emphasizes more the character of a mixer. The 2021 version emphasizes more the VCA character. Now you can choose. Both have their usage. I changed the mechanical structure as well for ease of construction. The front panel is now available with Gerber and *.fpd files as well.

It is basically a combination of 6 VCA configured as a mixer. The five inputs can be used as individual linear VCA or as input channels to the mixer output. All five input channels and the mixer output are voltage controlled. The control voltage inputs for the input channels are normalized so you can modulate all five channels with the same control voltage or group them to your needs. The inputs are normalized as well. This makes for a nice voltage controlled overdrive when used. A level indicator shows the output signal at the summed output. The summed output is voltage controlled as well. Instead of the here used CA3280 (I am using up some NOS) you can use the new available AS3280.

Specs and features

Five voltage controlled inputs
Five independent VCA
Voltage controlled output
Level indicator
Power consumption around 75mA each rail

Implementation

Schematic

Description:

On the schematics you can see 6 VCA with linear control current sources. Just as it is done over and over again. Plenty explanations on the web.

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Calibration

Set all sliders to zero
Attach a voltmeter or oscilloscope to the summed output
Set output slider to max
Adjust TR2 for zero Volt at the output
Let the output slider stay at max
Set the slider of channel one(2, 3, 4, 5) to max
Adjust TR1 (TR3, TR4, TR5, TR6) for zero Volt at the output
Set the slider of channel one(2, 3, 4, 5) to back to zero

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Building hints

None

Special parts

Instead of the here used CA3280 (I am using up some NOS) you can use the new available AS3280.
The sliders are from Befaco (Thonk)
The connectors are Thonkicons (Thonk)