[sdiy] variable compression

[Brock Russell]

>Has anyone seen a reliable way to wire up a NE570 as a compressor or
>automatic gain control in such a way that compression can be varied with a
>pot? I seen it done with fixed resistors, but the resultant matrix is way to
>complex to convert to pots.

Philips AN174 http://www.semiconductors.com/acrobat/applicationnotes/AN174.pdf
(or Signetics AN174 if you have really old databooks like me) Figure 18 - 
variable slope
compressor-expandor. Varies from 2:1 to 1:2.
Automatic level control Figure 17.

Brock