The following diagram is the circuit diagram of VOX Treble Booster. Vox made a variety of boosters that were meant to be plugged directly into amps or guitars.
Original VOX Treble Booster diagram:
Modified VOX Treble Booster diagram:
The modified circuit diagram is purposed to be used as an overdrive/distortion unit.
The input capacitor is changed from 500pF to 0.01 uF (1000pF) or 0.022 uF (2200 pF) to allow more bass in. This usually overloads the booster and causes crunchy distortion.
Download VOX Treble Booster circuit in PDF format