DC Transfer function problem...

[Don Tillman]

   Date: Thu, 21 Nov 96 09:17:56 PST
   From: Tim Cockram <tim at redragon.demon.co.uk>

   The control side-chain can either be feed forward or feed back (dbx
   tend to use feed forward most others use feed back).  The feed forward
   loop has some advantages but requires more thought to get it
   working properly (it does have lots of scope for wave distortion
   though!). 

There are two very important reasons to use feedback:

1.  It sounds a little funkier, and you just like that sound.

2.  If the circuit is the encoder end of a compression/expansion noise
reduction (or similiar) system.  That way, both the encoding and
decoding VCAs are driven off the same level-detector signal, and so
the total process avoids a certain set of dynamic distortion.

This: 

      |\                       |\
   ---| >-----+----> >---+-----| >--+--->
      |/      |          |     |/
       |      |          |      |
       +--LD<-+          +->LD--+

Instead of this:

            |\                |\
   ---+-----| >-----> >-+-----| >---->
      |     |/          |     |/
      |      |          |      |
      +->LD--+          +->LD--+


  -- Don