The Particle Germanium Fuzz is an adaptation of the Interfax HP-1 Harmonic Percolator, an extremely rare and highly sought-after fuzz/overdrive from the mid-1970s. Not much is known about the history of the unit other than that they were made in Milwaukee, Wisconsin by Ed Geise, owner of an electronics repair shop called Interfax Electronics.
The Harmonic Percolator is a two-transistor fuzz, but it bears no resemblance to any other of its contemporary pedals such as the Fuzz Face or any of the Tone Bender variants. It uses a PNP germanium transistor paired with an NPN silicon, allowing it to run in a standard negative-ground configuration. The transistors and some of the components were gooped or obscured in the original. Adding to the mystery, there were several circuit changes made throughout the run, so even if you manage to find one, there’s no guarantee that it’s one of the ‘good’ ones.
The Percolator was perhaps most famously associated with producer & musician Steve Albini as one of his “secret sauce” effect units. Curiously, his unit seemed to sound different from other Percolators, and when it was dissected, it was found to have several different values than others that had been traced. His is the only known unit to use these values.
Because of this, there are really two different versions of the Percolator, the “stock” version and the “Albini” version. Many people prefer the Albini version, and so those values are provided as the default configuration for the Particle. However, the alternate values for the stock version can also be used. The sounds are very different to the point where they’re almost two different pedals, so you may want to build both if you’re curious.
The Particle is an exact replica of the known schematics of the Harmonic Percolator, but with one addition. The Harmonic Percolator uses clipping diodes (unlike most germanium fuzzes) and so as with other Aion FX projects, we’ve added a diode switch to go between two different sets of diodes, or to disengage the diodes entirely.