The AFM-1 is an analog filter module designed by Tony Hardie-Bick. It's a modern interpretation of the Korg MS-10 and MS-20 filter. Tony provides a PCB including a single mono 12dB LP / 6dB HP filter, but it's designed to cascade well and can easily be set up in a stereo configuration.
My own version is based upon four of these filter boards, providing a stereo filter with two stages. I kept the configuration as flexible as possible: Each stage has a complete set of input/output jacks, enabling patching the filter as two independent stereo filters. Cascading the filters in series can either be done internally, bypassing the input pre-amp stage for the second stage, or through the normalised connectors, allowing to tweak the gain structure independently. Tweaking gain on this filter is crucial: It really comes to life when you overdrive the filter and turn up resonance. I then use the second stage to tame the sound - hence individual gain control is crucial. According to Tony, this is the "ultimate configuration" of the filter that nobody else has tried so far... ;-)
AFM Distortion Jam (12.3MB, 10:49) - A one-off jam session, pushing the AFM to the extreme.
Analogue Dreams (8.8MB, 9:40) - Studio production, inspired by the jam above, not going quite as far this time.