I've found this old article from a magazine. Doesn't seem like something ground-breaking but I'm always curious about those "public" schematics. I'm still a super-beginner at making layouts and I haven't been successful at this one.
Dunno if it's something you guys would be interested in making but I thought I'd suggest it anyhow.
Thanks!
http://rubidium.dyndns.org/cag/pdf/sf.pdf