Over the course of the past few years I've owned two Moog Prodigies. I got the first one about six years ago and modified it extensively. Eventually I sold it to buy the second one, which is covered in an older post.
Of all of the Prodigy's features, I've really just missed the warmth of the Moog transistor ladder filter. But I've been so completely satisfied with the EML101's sound and versatility in every other regard that I decided it would be best to simply build a VCF module based on the Moog design.
I've never had much patience for prototyping or for planned circuit board layouts. So, as I've almost always done, I let the schematics guide the arrangement of the parts as I went. It's the most challenging aspect of my electronics work.. but its a good exercise of creative problem-solving.
While checking local thrift shops for an enclosure, I found this old electric shoe-shiner. The 'Regina'-brand "Electric Shoeboy." It originally had an industrial-type motor inside and rotating brushes protruding from each side.
After removing the motor and the shaft, dremmeling the case, and super-gluing/epoxying cut-up aluminum to cover the holes, I had this finished enclosure! (The last image in this post was found on google to show approximately what this unit looked like before modification.)
I based my circuit on yusynth's plans, but changed a few component values for a greater range of control. I also had to scale the keyboard CV input for the EML101's 1.2V/Oct.
Here are a few sound samples:
E-mail me if you'd like me to build a synth module in an enclosure of your choice!