[sdiy] zero-to-unity gain (0 to +5V) VCA? (jhaible schemo)

[Amos]

Hello all,

I have a project in mind which involves modding an fx pedal so that its
input level can be cv-controlled with an expression pedal, to go from no
input being passed (full attenuation), to unity-gain (no attenuation) as the
CV-in is swept from 0V to +5V.
A google search netted this not-entirely-dissimilar schematic from JH:
http://www.oldcrows.net/~jhaible/tonline_stuff/hjvcaod.gif<http://www.oldcrows.net/%7Ejhaible/tonline_stuff/hjvcaod.gif>

However, all I need my circuit to do is what I described above.  I am very
much a novice to circuit design, although I am getting progressively better
at fixing already-existing circuits...  can anyone provide some pointers or
methods to accomplish my task?  I don't have a good enough concept of VCA
operation yet...

Thanks very much.

-Amos
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