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