The Harmonic Percolator is a distortion pedal that was made in Milwaukee Wisconsin in the 1970's. It used a silicon NPN transistor and a germanium PNP transistor in a design that passes even order harmonics while suppressing odd order harmonics. These even order harmonics are more pleasing to the ear than odd order harmonics.This is the original circuit, not someone’s interpretation of it. The left slider is the input gain or distortion control and the right one is the Balance control. The input is on the left and the output is to the right when looking down on it. This is opposite pedals of today but in its time this made sense. Left to Right - the same way you read. This EXACT handmade duplicate of the original 1970's pedal employs the same obsolete number Germanium transistor and same number Silicon transistor. (Op Amps were never used in Percolators) The silicon transistor was potted in the originals to discourage people from reading the number on it! Also used are the exact same number obsolete Germanium diodes. (They are NOT the common 1N34 or 1N60) Same type capacitors also are used. Mylar-Silver Mica, Tantalum, and Ceramic. The slider controls are the same as in the original. These New Old Stock parts have the original packing slip dated February 19, 1968! Three original pedals were dismantled to help create this duplicate. One Percolator was totally dismantled, all its parts removed and measured. (Thanks John D. Greg K. Rusty B. @ Rockhaus Guitars and Jay T. for trusting your pedals to me!). I am sure it was unsettling for the one original Percolator owner to have his pedal dismantled, the transistor removed AND heated up to about 150 degrees to loosen the wax holding the metal ring obscuring the part number. There are no hidden parts, no mis-labeled components, nothing unusual beyond the circuit itself! Legendary guitar-abuser Steve Albini (Shellac, Big Black, Rapeman) uses a Harmonic Percolator and calls it a great labor saving device! See the Gearwire videos! This is known to be the same circuit version he uses! At low settings the Harmonic Percolator will give you added sustain without 'coloring' your sound. Higher settings will give a mean distortion that performs well with multiple notes. These duplicates are in the exact same case and finished with a super tough powder coating in the original tan and brown style.