The Oltretomba fuzz is based on a Vox Tonebender, the Italian two transistor version, referred to as "Model 50" on the serial number label.
The unit used for reference to these recreations is an early example from 1966, with a larger value output capacitor than later models. It also has a different transistor compliment than the norm, an AC107 and an AC135. The tone is looser and raspier than the more common later versions.
This version uses Newmarket MT57 and a Tunsram AC125, these transistors have been tested for gain and leakage, sorted into matched pairs and auditioned in a test box to ensure they behave as expected.
The tone is very close to that of the reference unit, thicker than the average Italian Vox Tonebender, but without being mushy on the low strings. The fuzz is beautifully responsive to pick attack and cleans reasonably well from the guitars volume control.
The pedal requires a 9v battery, there is no provision for an external power supply.