MN3005, MN3007 BBD.. anyone built one?

[Chris & Ann MacDonald]

> I was puzzling over what the NE570N
> compander was doing there. Is it normal 
> to compress the signal before it
> goes through the delay stage?

Compression at input followed by expansion at output is a noise
reduction technique.  Here's my non-technical understanding of this
process: Basically you compress the signal before it enters a device
which introduces noise (like a delay line), then expand the signal after
it leaves the device.  This (ideally) causes no change in the desired
signal, but the noise which was introduced while the signal was
compressed will become proportionally quieter to the desired signal
after expansion.

-Chris M.