CORVUS DISTORTION / SUSTAINER
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 Corvus Fuzz is a clone of the 1977-1980 “op-amp” EHX Big Muff Pi, a redesign of the classic Big
Muff circuit using op-amps instead of transistor gain stages. It was designed by Howard Davis, a brilliant
EHX engineer who also invented the Memory Man delay and Electric Mistress flanger as well as the
Deluxe Big Muff Pi.
He was tasked in the redesign with getting a similar sound to the Big Muff, but the circuit itself bears no
resemblance to the earlier 4-transistor circuit apart from the tone control. Therefore, while it was the
only commercially-available version of the Big Muff for several years, today it’s seen as a fully separate
circuit. (In 2017, EHX reissued this version of the Big Muff, formally adopting its formerly unofficial
name, the “Op-Amp Big Muff Pi”.)
The Corvus is based on the 1978 revision of the Big Muff, which added a “Tone Bypass” switch. As
inferred by the name, this switch fully bypasses the tone stack for a more raw and grinding sound.
The Corvus is a direct adaptation of the 1978 circuit except for the inclusion of an optional modification
to the gain control, originally conceived by Analogguru. This converts the op-amp configuration into a
variable gain stage, whereas the stock unit uses a fixed gain configuration followed by a volume control.
With this modification, the op-amp isn’t amplifying the signal any more than it needs to. However, the
original version can also be built if you prefer (see build notes for details).
USAGE
The Corvus has the following controls:
•
Sustain
controls the amount of gain that is fed into the clipping stage.
•
Tone
pans between a low emphasis and high emphasis, with an overall scooped tone in the middle.
•
Tone Bypass
(toggle switch) bypasses the tone stack entirely, increasing the output level and giving
it a more aggressive bite.
•
Volume
is the overall output level.
