PLASMA VINTAGE DRIVE
2
TABLE OF CONTENTS
1
Project Overview
7
Drill Template
2
Introduction & Usage
8
Enclosure Layout
3-4
Parts List
9
Wiring Diagram
5
Build Notes
10
Licensing
6
Schematic
10
Document Revisions
INTRODUCTION
The Plasma Vintage Drive is a clone of the Colorsound Overdriver, a transistor-based boost/drive pedal
with 2-band tonestack that was first sold in 1972.
The Overdriver was an updated version of the Power Booster from 1970. The Power Booster ran at 18V
using two batteries in series. The Overdriver dropped the requirement of the second battery and ran on
a normal 9V supply. There were a few other very minor tweaks to component values, but it’s the same
basic circuit.
The Plasma project is a direct clone of the Overdriver, but with one modification: it adds an output
volume control. This way you can set the gain according to the tone you want without being tied to the
volume that is produced along with it.
Note that the Overdriver can be “splatty” at medium gain levels as the notes decay. It works best at low
gain as a clean boost with tone-shaping capabilities, or at high gain where it’s not unlike a Big Muff. If you
hear this splattiness, know that it’s a byproduct of transistor-based distortion and it’s working correctly!
The 125B version of the Plasma is different from the first version in that it drops the Power Booster
compatibility. The Power Booster is instead available as another circuit, the Nucleus, which has an on-
board charge pump for 18V operation. In addition, in this updated version, the transistor bias trimmers
have been removed. It’s not necessary to bias the transistors in the Overdriver circuit for correct
operation.
USAGE
The Plasma has two controls and one toggle:
•
Gain
controls the amount of gain from the first transistor stage.
•
Treble
controls the high-end response of the circuit and forms half of the Baxandall tone stack.
•
Bass
controls the low-end response of the circuit and forms the other half of the Baxandall tone
stack.
•
Volume
is the output volume of the effect.
