[sdiy] NE571N compander from "The Electronic Goldmine"

[JH.]

> The chips were never regarded for their heroic audio quality. 

That's true, but keep in mind that you normally use companders
to interface parts of a signal chain that don't have "heroic audio
quality" (I like the word!) themselves, so as long as the compander
is not the weakest link in the chain, who cares.

It's interesting that for *both*, compressor and expander applications
of the NE57x chips, the VCA input sees the reduced dynamic range,
so you don't need any outrageous SNR for the VCA!

It does help to replace the slow internal opamp of the 570/571
with a better one (NE5532 etc.). This is possible - see app notes.
(The later NE572 chip doesn't have an internal opamp at all.)

JH.