PARHELION VINTAGE OVERDRIVE
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 Parhelion Vintage Overdrive is based on the Boss OD-1 OverDrive, originally released in 1977 as
one of their first compact pedals alongside the SP-1 Spectrum and PH-1 Phaser.
The OD-1 is notable for being the first overdrive effect to utilize diodes in an op-amp’s negative
feedback loop for clipping purposes. Like the Dis, it lacks a tone control, but most who play
through it say it doesn’t need one.
The OD-1 had two different versions. The original 1977 version used the Raytheon RC4303 quad
op-amp (called the “quad version”). The second version from December 1980 used a single 4558 dual
op-amp (the “dual version”) and changed the input & output buffers to transistor emitter followers as a
cost-savings measure, as in most of their later pedals. The original quad version is said to sound better
and is what the Parhelion project is based on.
While the RC4303 is long out of production, they can still be found without too much trouble. They
share a standard pinout with other quad op-amps such as the LM324 and LM348, so there are many
other options that will perform similarly.
The Parhelion has two toggle switches allowing for a little more flexibility. A clipping switch selects
between three different sets of diodes, and an EQ switch changes the gain structure of the op-amp
clipping stage for higher gain and more bass.
Note: The legacy 1590B version of the Parhelion was called the Corona. The updated version was given a new
name upon release in 2021 for obvious reasons.
USAGE
The Parhelion has the following controls:
•
Drive
controls the amount of gain in the op-amp feedback diode clipping stage.
•
Volume
controls the overall output of the effect.
•
Clip
(toggle switch) selects between three sets of diodes: 1x silicon (stock), 2x silicon, and LEDs.
•
EQ
(toggle switch) selects between two different tones: stock mode (similar to the Tube Screamer)
and another mode with slightly higher gain and less bass cut.
