Four chanel TH VCA-1 question?

[Strazdas]

I'm about to build four TH VCA's in one unit, but would like to have it as a mixer too. I'm mean like oakley Quad Voltage Controlled Amplifier and Mixer http://www.oakleysound.com/vca-d.htm

If the output socket of any VCA channel is unused then that signal will be mixed with the output of the final channel. However, any VCA channel can simply be taken out of the mixing process by inserting a jack lead into its respective output socket.

To do this, can I add 4 x 100k summing resistors before IC2B and increase R8 to 100k (or other value) (also adding one 100k before IC2b and 100k resistor instead of R8 in 1,2 and 3-rd VCA), or should I build separate mixer with 071 with fourth VCA always connected to it?

Many thanks.

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schem.jpg
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[fonik]

the major change to the circuit is the input resistor for the inverting buffer (R5 on your schematic for VCA's 1-3).
in general i see no problem, however, watch out for the correct resistor values that give you the output level you need.

EDIT: outputs of VCA's 1-3 will be inverted when mixed with VCA #4. is this intended or no problem at all for you?

[Strazdas]