aion Nereus User manual

NEREUS OCTAVE FUZZ 1
PROJECT NAME
NEREUS
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Catalinbread Octapussy
A vintage-inspired octave-up fuzz in the tradition of the Roger Mayer Octavia.
Octave-up fuzz 1.0.0 (2023-11-24)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

NEREUS OCTAVE FUZZ 2
TABLE OF CONTENTS
1Project Overview 7Drill Template
2Introduction & Usage 8Enclosure Layout
3-4 Parts List 9Wiring Diagram
5Build Notes 10 Licensing
6Schematic 10 Document Revisions
INTRODUCTION
The Nereus Octave Fuzz is based on the Catalinbread Octapussy, an octave-up fuzz that was first
released in 2012 and traced by Aion FX in 2023.
The Octapussy was called an original circuit, though they hinted that it was related to the Octavia.
Based on our trace, this is perhaps stretching the truth a bit since the front half of the circuit is very
similar to a silicon Fuzz Face and the octave section is directly lifted from the Octavia.
There are some interesting twists, though, and the end result is undoubtedly better than the sum of its
parts. The Fuzz Face input section has a unique feedback arrangement that acts as a tone control and
softens the fuzz somewhat, and prepares the signal for a better octave in the following stage.
The Nereus is directly based on our trace of the Octapussy. The only change we made was to reverse the
orientation of the output volume control, which was called “Attenuation” on the original and reduced
the volume as it was turned up—most likely a marketing decision on their part to make it seem louder.
USAGE
The Nereus has the following controls:
• Gain sets gain of the fuzz stage.
• Body controls the frequency of the negative feedback path in the fuzz stage, which cuts highs and
emphasizes low frequencies as it’s turned up.
• Volume sets the volume level at the output.

NEREUS OCTAVE FUZZ 3
PARTS LIST
This parts list is also available in a spreadsheet format which can be imported directly into Mouser for
easy parts ordering. Mouser doesn’t carry all the parts (most notably potentiometers) so the second tab
lists all the non-Mouser parts as well as sources for each.
View parts list spreadsheet →
PART VALUE TYPE NOTES
R1 120k Metal film resistor, 1/4W
R2 6k8 Metal film resistor, 1/4W
R3 150k Metal film resistor, 1/4W Carbon comp measured 159.8k in original circuit. See build notes.
R4 1k8 Metal film resistor, 1/4W
R5 470R Metal film resistor, 1/4W
R6 130R Metal film resistor, 1/4W
R7 15k Metal film resistor, 1/4W Carbon comp measured 17.1k in original circuit. See build notes.
R8 470k Metal film resistor, 1/4W
R9 220k Metal film resistor, 1/4W
R10 10k Metal film resistor, 1/4W
R11 10k Metal film resistor, 1/4W
R12 2M2 Metal film resistor, 1/4W
R13 100k Metal film resistor, 1/4W
R14 680k Metal film resistor, 1/4W
R15 100k Metal film resistor, 1/4W
R16 100k Metal film resistor, 1/4W
R17 100R Metal film resistor, 1/4W Power supply filter resistor.
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor. Can be as low as 1M.
LEDR 10k Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 1n Film capacitor, 7.2 x 2.5mm
C2 33n Film capacitor, 7.2 x 2.5mm
C3 47pF MLCC capacitor, NP0/C0G
C4 22uF Electrolytic capacitor, 5mm
C5 22uF Electrolytic capacitor, 5mm
C6 1n Film capacitor, 7.2 x 2.5mm
C7 680n Film capacitor, 7.2 x 4.5mm
C8 470n Film capacitor, 7.2 x 3mm
C9 2.2uF Film capacitor, 7.2 x 5mm Can also use electrolytic (polarity marked on PCB).
C10 2.2uF Film capacitor, 7.2 x 5mm Can also use electrolytic (polarity marked on PCB).
C11 68n Film capacitor, 7.2 x 2.5mm
C12 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C13 100n MLCC capacitor, X7R Power supply filter capacitor.

NEREUS OCTAVE FUZZ 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
D1 1N5817 Schottky diode, DO-41
D2 1N914 Fast-switching diode, DO-35
D3 1N914 Fast-switching diode, DO-35
Q1 PN2222A BJT transistor, NPN, TO-92 Can substitute PN2222 or 2N3904.
Q2 PN2222A BJT transistor, NPN, TO-92 Can substitute PN2222 or 2N3904.
Q3 PN2222A BJT transistor, NPN, TO-92 Can substitute PN2222 or 2N3904.
TRIM 100k trimmer Trimmer, 10%, 1/4” See build notes for how to set this trimmer.
GAIN 5kC 16mm right-angle PCB mount pot Reverse audio (reverse log) taper.
BODY 500kA 16mm right-angle PCB mount pot Audio (log) taper.
VOLUME 500kB 16mm right-angle PCB mount pot Linear taper.
IN 1/4" stereo 1/4" phone jack, closed frame Switchcraft 112BX or equivalent.
OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
BATT Battery snap 9V battery snap Optional. Use the soft plastic type—the hard-shell type will not fit.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

NEREUS OCTAVE FUZZ 5
BUILD NOTES
Setting the bias trimmer
The bias trimmer sets the voltage at the base of Q3. Assuming a 9.6V supply voltage, the trimmer’s
range is 3.06V to 3.88V. We’re not sure how Catalinbread determined the optimum setting, but in
the unit we traced, the trimmer was set to 21.5k (21% rotation), which would be 3.26V. Feel free to
experiment and see if you notice any significant difference, but otherwise just set it to that position and
forget about it.
Volume knob rotation
The original Octapussy has a knob labeled “Attenuation”, which is nothing more than a reversed volume
knob that reduces the output as it’s turned up. We have reversed this in the Nereus so it acts as a
traditional volume control.
Transistor substitutions
The Octapussy uses PN2222A transistors, which are a TO-92 version of the 2N2222A (TO-18 metal
can). This is a low/medium-gain NPN transistor that is almost identical to the 2N3904, which can be
substituted with no change in tone.
The “A” suffix designates higher maximum voltage and temperature, but the electrical properties are
otherwise is identical between the two versions. The non-”A” PN2222 is available from Aion FX.
Resistor substitutions
The original circuit used carbon composition resistors for R3 and R7. This type of resistor is notorious
for drifting over time. We measured these two resistors in the unit we traced and found that the 15k
resistor (R7) measured 17.1k, and the 150k resistor (R3) measured 159.8k. Both are 5% tolerance, but
R7 is 14% above nominal and R3 is +6.5%.
We do not recommend using carbon comp resistors when building this circuit, but if you want to
replicate the sound of the unit we traced, you can use a 17k metal film resistor for R7 and a 160k metal
film resistor for R3, which are the nearest precision values.
Electrolytic vs. film capacitors
The original Octapussy uses 2.2uF electrolytic capacitors for C9 and C10. We try to avoid electrolytics
in the signal path where possible, so the PCB layout uses non-polar film caps. However, if you do want to
use electrolytics as in the original, the polarity has been marked on the PCB. Otherwise, these polarity
marks can be ignored.

SCHEMATIC
NEREUS OCTAVE FUZZ 6
GND
2M2
1N5817
100uF
500kA
5kC
GND
500kB
+9V
100n
VA
1n
33n
120k
GND
PN2222A
47pF
VA
6k8
22uF
GND
GND
150k
PN2222A
1k8470R
22uF
130R
GND
GND
VA
1n
15k
680n
470n
470k220k
VA
GND
100k
PN2222A
10k
VA
10k
GND
2M2
680k
2.2uF
2.2uF
1N914
1N914
100k
100k
GND
GND
100k
GND
68n
GND
100R
IN
OUT
RPD
D1
C12
BODY
1
2
3
GAIN
1
2
3
VOLUME
1
2
3
C13
C1
C2
R1
Q1
C3
R2
C4
R3
Q2
R4R5
C5
R6
C6
R7
C7
C8
R8R9
TRIM
1
2
3
Q3
R10R11
R12
R14
C9
C10
D2
D3
R13
R15
R16
C11
R17
GND

NEREUS OCTAVE FUZZ 7
DRILL TEMPLATE
Cut out this drill template, fold the edges and tape it to the enclosure. Before drilling, it’s recommended
to first use a center punch for each of the holes to help guide the drill bit.
Ensure that this template is printed at 100% or “Actual Size”. You can double-check this by measuring
the scale on the printed page.
Top jack layout assumes the use of closed-frame jacks like the Switchcraft 111X. If you’d rather use
open-frame jacks, please refer to the Open-Frame Jack Drill Template for the top side.
LED hole drill size assumes the use of a 5mm LED bezel, available from several parts suppliers. Adjust
size accordingly if using something different, such as a 3mm bezel, a plastic bezel, or just a plain LED.
0 1 2
CM
0 1
INCH
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: 0, y: +0.66
ø9/32”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
125B
VOLUME
BODY
GAIN
FOOTSWITCHLED

NEREUS OCTAVE FUZZ 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

NEREUS OCTAVE FUZZ 9
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT
Shown with optional 9V battery. If battery is omitted, both jacks can be mono rather than one being stereo.
Leave the far-right lug of the DC jack unconnected.

NEREUS OCTAVE FUZZ 10
LICENSE & USAGE
No direct support is offered for these projects beyond the provided documentation. It’s assumed
that you have at least some experience building pedals before starting one of these. Replacements and
refunds cannot be offered unless it can be shown that the circuit or documentation are in error.
All of these circuits have been tested in good faith in their base configurations. However, not all the
modifications or variations have necessarily been tested. These are offered only as suggestions based
on the experience and opinions of others.
Projects may be used for commercial endeavors in any quantity unless specifically noted. No
attribution is necessary, though a link back is always greatly appreciated. The only usage restrictions
are that (1) you cannot resell the PCB as part of a kit without prior arrangement, and (2) you cannot
“goop” the circuit, scratch off the screenprint, or otherwise obfuscate the circuit to disguise its source.
(In other words: you don’t have to go out of your way to advertise the fact that you use these PCBs, but
please don’t go out of your way to hide it. The guitar effects industry needs more transparency, not less!)
DOCUMENT REVISIONS
1.0.0 (2023-11-24)
Initial release.