Silicon Harmonic Percolator
Fredric Effects have been building a part-for-part clone of the original 1970s Interfax Harmonic Percolator for over a decade now, and an improved version of that hybrid Silicon/Germanium circuit as the Utility Perkolator for almost as long.
The Harmonic Percolator circuit is simple and versatile, and careful component selection can yield fascinating results. This modified version of the Harmonic Percolator uses entirely silicon transistors manufactured 40 years ago in the former East Germany, and clips the signal using a weirdo East German diode array.