[sdiy] very simple VCA circuit

[David G. Dixon]

> I uploaded my saved image here:
> 
> http://www.sdiy.org/peng/diy/Mike%20Sims%20VCA.gif
> 
> It's small and hard to read but that's all I have.

Thanks for that, megaohm.  Now I remember thinking about this about two
years ago.  Given the price differential between LM13700 and SSM2164, it
might be worth it to consider this circuit.  However, the linearized 2164
requires no trimming (and you can always get exponential response out of it
as well, or anything inbetween).