As you can see. it's pretty simple. It utilizes a quad op amp, some resistors and whole bunch of diodes. If you check out that page I link to above, you'll find 2 pcb layouts ready to go. One is for a single Fritz AD/AR generator and the other is for a dual. I opted for the dual.
Then I put the panel together. The layout is a little strange but it's what worked best for mounting the PCB. I picked up that Angle aluminum from the hardware store, I just cut off the length I need with a hacksaw and drill holes in it. works great. It also makes the modules more rigid, which is nice.
Etched the PCB and drilled all the tiny holes. I guess I should do a post on etching PCB's pretty soon. Totally easy.
In the video, I use the top Envelope to control the VCA and the bottom to control the Filter.