aion AURUM Manual - Page 2
Browse online or download pdf Manual for Music Pedal aion AURUM. aion AURUM 12 pages. Based on boss od-2 turbo overdrive
Print PageTABLE OF CONTENTS
1 Project Overview
2 Introduction & Usage
INTRODUCTION
The Aurum Amp Overdrive is based BOSS
Boss's "discrete op-amp" circuit topology which uses two JFETs and a PNP transistor to create a variable
gain stage that can be controlled like an op-amp but clips gracefully when overdriven. As a bit of trivia,
the OD-2 is also one of only three fully discrete circuits ever made by BOSS (no op-amps), alongside the
FZ-3 Fuzz
and the DS-2 Turbo Distortion.
The OD-2 was first released in 1985 as the successor to the OD-1. In 1994, it was replaced by the OD-
2r. The "r" in this case stands for "remote", since it allowed an external footswitch to change between the
two channels on the fly. However, the OD-2r also corrected one one of the most persistent flaws of the
original unit, which is that it could barely get to unity gain at the highest volume setting.
The Aurum is more specifically based on the "Turbo" mode of the circuit, adapting the OD-2r version
of the circuit with the gain recovery stage and a couple of other minor tweaks. The non-"Turbo" mode
is a completely separate drive circuit within the pedal, and generally speaking it's unremarkable when
compared to the Turbo mode.
The OD-2 was officially succeeded by the OD-3 in 1997, although the BD-2 Blues Driver can be seen as
a "rebranded" in-between member of the same series since it shares much of the same circuitry as both
the OD-2 and OD-3. However, all three circuits sound pretty different, and they each bring their own
character to the table.
The original OD-2 uses the 2SK117-GR JFET, a low-cutoff type similar to J201, but no longer made in
through-hole format. 2SK209-GR is the SMD version that is still in production and will perform exactly
the same as the originals. Each of the JFETs have extra pads for soldering SMD parts, but if you don't
feel confident in your SMD skills, Aion FX sells
through-hole applications.
USAGE
The Aurum has three controls:
• Drive increases the gain of the first discrete op-amp stage, which overloads the second stage and
pushes it into clipping.
• Tone is a passive treble cut after the second gain stage.
• Volume sets the overall output of the effect signal.
AURUM AMP OVERDRIVE
12 Licensing
®
OD-2 Turbo Overdrive, notable as the first appearance of
2SK209-GR pre-soldered to adapter boards
to be used in
2