Monad - Univox Uni-Drive Guitar Pedal PCB



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Project overview

The Monad Vintage Boost is an adaptation of the Univox Uni-Drive UD-50. The original Uni-Drive was in a wah-style enclosure, with the foot pedal controlling the overall volume and a rotary switch setting the input attenuation (which corresponds to the amount of transistor clipping that occurs). It also had a range knob to allow the user to set the minimum position of the volume treadle to tailor it to their liking.

Since the rotary switch is set up as a potentiometer with six fixed positions, in this project it has been converted to an actual potentiometer. And since the range control is only needed for a treadle, it’s been omitted and merged into the output volume control.

Along with those changes, two modifications have been added. The first is an input capacitor blend control, allowing you to reduce the bass content for more of a treble boost than full-range. This is a common modification for vintage pedals with no tone control, often seen on variants of the Fuzz Face and Dallas Rangemaster.

The second modification is an internal trimmer that allows you to adjust the amount of feedback from the third stage back to the first stage. The default resistor is 8.2k in the original, but by setting it higher or lower, you can get some interesting tonal changes.