VCA designs

[Grant Richter]

>I usually just lurk in the background, but in this case I'm throwing
>my 2 cents in, but I would also like to see any good VCA
>designs ( high dynamic range/low noise ) that anyone has.
>

Just got done doing a design based on the CA3280, some comments:

Control voltage rejection is fantastic, can't measure it but "thump" is way down
compared to any other design I've tried (3080, discrete).

Goofed around with Id by ear, the 68K value in the app. note does seem to
be optimum for 10V p-p. James Patchell uses 82K in his design in
Polyphony Jan/Feb 1980 pg. 12 but he's also using 5V p-p.

Harmonic distortion is surprisingly audible. Specs say 0.4% which is
audible in sine waves at 10V p-p decreases with amplitude.
Seems to be primarily second harmonic.

Still it's a premium upgrade over 3080 designs at least as far as signal to noise
ratio is concerned.

Anybody built a LM13600 design that has comments?