[sdiy] Companders

[Scott Stites]

Wow,
A lot of good information.  Thank you all, I guess I have a lot of homework to do!

Scott


===================
Paul Perry wrote:

Analog Devices do some. But usually only surface mount.
For discrete compressors, check the guitar effect circuits
(search for "doctor Q")

===================

Craig Critchley wrote

That Corp. has the THAT4301 analog processor, which contains an RMS
detector, an exponential VCA and three opamps (one is dedicated as a
current-to-voltage converter for the VCA).  The primary purpose for it is
audio compressors. Its several building blocks on a chip, rather than a
purpose-dedicated device, so it might be more flexible.

Unfortunately That only sells multiples of 20 (one tube), and they aren't
distributed through any of the normal online distributors that I'm aware of.
They are also more expensive, in that quantity, that the SA571 price you
found, but it is designed for audio rather than telecoms, so it may have
better specs.

Another possibility is Analog Devices's SSM2165 and SSM2166, which are
microphone preamps that include compressor circuits.  I think those can only
be used as compressors, though, and I don't think they're cheaper.

===================

Steve Ridley wrote:

There are better solutions than the NE571.  Take a 
look at:

www.thatcorp.com

and look at their "Analog Engine" dynamic processors
and application notes and design notes.  More info
than you can shake a stick at.  That Corporation were
formerly the semiconductor part of DBX, so they know
a bit about compression and noise reduction.

You could also look on the Perkin Elmer (formerly Vactec)
site.  They make vactrols and have an extensive data sheet
on how to use them in dynamics control.  Go to:

http://optoelectronics.perkinelmer.com

and search for Vactrols.



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