This is a very interesting project I first learned about from the Prodigy-Pro forum. As luck would have it, this project came along about the time I was beginning work on my own version of the SSL 4000 Buss Compressor.
The project was created by Jakob Gyraf of Gyraf Audio and is well documented on the Prodigy-Pro forum. The sound of the unit is fairly true to original although I can tell some differences in how the sidechain circuit reacts, particularly to material with a lot of low end. Apparently I'm not the only one to hear this as there are several mods and hot-rods for this project. I'm building a second unit now and will incorporate the SuperSideChain mod (also discussed on the forum.) in it. I may also mod this unit depending on how useful the mod is.
Here's a look at the inside of the unit. The board to the left of main board provides a true hardware bypass function implemented using sealed relays. The relays have their own power supply to help keep the noise to a minimum.The VCA's I used on this project, dbx 202C's, are the ones used in the SSL 4000 console as well. They are the rectangular gold cans on the left side of the main board. I used Mogami cable for all audio path wiring and gold-plated XLR's on the back panel. Overall, a very satisfying project!
A closeup of the main board and dbx 202C VCA's.
A closeup of the relay board for the hardware bypass function. This turned out to be a pain in the butt to implement but is also very useful for making sure I'm not over-using the unit on mixes.