The original Percolator was designed in Milwaukee Wisconsin in the 1970s as an original circuit not based on anything previously available in that era.
With a silicon PNP transistor and a germanium PNP transistor, the circuit passes even order harmonics while suppressing odd-order harmonics. These even order harmonics are more pleasing to the ear than odd-order harmonics.
This board allows you to build two different versions of the same pedal:
- The Stock version is much more wild, raw, and hard to control. It delivers an over-compressed sound. Also is more prominent to be noisy than the Albini version.
- The Albini version is smoother and more controlled, which reminds of an aggressive Fuzz Face with unique characteristics. When the Harmonic know is all the way up, it can get really compressed as well
This version features an additional toggle switch to select in between the stock diodes and some extra of your choice. You can play around with some 3mm Red LEDs for a louder sound and less compressed drive, or with some other germanium diodes for a compressed and creamy tone.
There’s no definitive ideal hFE for the Germanium 2N404 in the circuit, but based on our experience with the circuit, anything between 40-60 sounds great – nice and crunchy with plenty of focus. As the gain gets higher it gets a little unruly and gets some noise, at this point, it also starts to get the microphonic behavior that can be a really interesting tool.
As the 2N404 is almost unobtainable we are currently testing with some other germanium alternatives. The results will be published on the next update of the docs.
- Balance: This controls the output level of the pedal. It works just like the volume knob on your guitar or your amp.
- Harmonics: Is the input gain or distortion control, at the same time controls the Harmonics response.
- Diode Switch: Select between the stock 1n695 and your choice of clipping diodes
For further analysis on this circuit take a look at this thread on Free Stomp Boxes Forum