[sdiy] LM13600 VCA

[John Blacet]

If you use the 15K diode bias resistor, the 13600 can handle more input.
In this case, the input resistors are generally set to give a max of
100mV with your largest expected input signal. Take a look at the NS
data sheet graphs to get an idea of distortion vs input level.

I would not use the onboard buffer; use a TL074 instead.

CV circuits are out there for both linear and expo response; the single
PNP is of course very temperature dependent. A dual PNP circuit would be
better. A tempco resistor is ideal but seldom used.

The amount of noise could be a factor. You might want to think about
some way to automatically drop the gain on channels that have no signal!
Breadboard a four channel unit and check it out.

The SSM2164 quad VCA might be a bit better in terms of noise and the
inputs are expo. You have to do some scaling and inverting for 0-5 or
10V control ranges.

Regards,
___________________
John Blacet
Blacet Research
http://www.blacet.com