aion CERULEAN User manual

CERULEAN AMP OVERDRIVE 1
PROJECT NAME
CERULEAN
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Marshall Bluesbreaker
A classic overdrive effect that was designed to mimic the Marshall Bluesbreaker amplifier from the
1960s, the Bluesbreaker is also the source circuit for a number of high-dollar “boutique” guitar pedals.
Amp-Like Overdrive 1.1.0 (2020-05-18)
Actual size is 2.3” x 1.86” (main board) and 2.3” x 0.86” (bypass board).
BUILD DIFFICULTY
Easy

CERULEAN AMP OVERDRIVE 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 Cerulean Amp Overdrive is an updated version of the Marshall Bluesbreaker pedal. The
Bluesbreaker is the source circuit for a number of expensive boutique pedals including the Analogman
King of Tone (which is two Bluesbreakers in the same box with a few modifications).
The Cerulean project has integrated two of the modifications from the King of Tone: the Presence
control (an internal trimmer) and the ability to control both the soft clipping (stock) and hard clipping
diodes. The clipping switches have been expanded further to allow two different diode combinations for
both hard and soft clipping, whereas the King of Tone only has “on” and “off” settings for each.
Another notable clone of the Bluesbreaker is the JHS Morning Glory, which added a JFET gain stage at
the end for increased output volume. The Cerulean project provides the option of using the output stage
of the Morning Glory. See the build notes for more information.
During the development of this updated version of the Cerulean, it was determined that the “Bright”
switch of the Morning Glory was not very useful, especially when there was already a Tone control and
an internal Presence control, both of which affect the high end. The original Bluesbreaker doesn’t filter
out any of the treble in the clipping stage, so in fact the Morning Glory is really no brighter than a stock
Bluesbreaker, and instead only adds the option to get darker. Accordingly, this option has been removed
in favor of simplifying the decisionmaking process when deciding how to build it.
However, if you do want to make an exact clone of the Morning Glory including the Bright switch, you
can use the earlier version of the Cerulean which will continue to be available for the foreseeable future.
USAGE
The Bluesbreaker has the same control layout as most overdrive or distortion effects:
• Tone controls the treble response of the effect.
• Drive controls the amount of gain in the op-amp feedback diode clipping stage.
• Volume controls the overall output.
• An internal Presence control allows you to tweak the overall response of the tone knob.
• Soft Clipping lets you choose between stock clipping diodes, LEDs, or no soft clipping.
• Hard Clipping lets you select high-threshold hard clipping, low-threshold hard clipping, or none.

CERULEAN AMP OVERDRIVE 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—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 1M Metal film resistor, 1/4W
R2 3k3 Metal film resistor, 1/4W
R3 4k7 Metal film resistor, 1/4W
R4 10k Metal film resistor, 1/4W
R5 220k Metal film resistor, 1/4W
R6 6k8 Metal film resistor, 1/4W
R7 1k Metal film resistor, 1/4W
R8 6k8 Metal film resistor, 1/4W
R9 47k Metal film resistor, 1/4W
R10 47k Metal film resistor, 1/4W
RX1 100k Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RX2 68k Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RX3 1M Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RX4 22k Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RX5 12k Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RX6 12k Metal film resistor, 1/4W Part of the optional Morning Glory gain stage. (see build notes)
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor. Can be as low as 1M.
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 10n Film capacitor, 7.2 x 2.5mm
C2 47pF MLCC capacitor, NP0/C0G
C3 10n Film capacitor, 7.2 x 2.5mm
C4 10n Film capacitor, 7.2 x 2.5mm
C5 100n Film capacitor, 7.2 x 2.5mm
C6 10n Film capacitor, 7.2 x 2.5mm
C7 10n Film capacitor, 7.2 x 2.5mm
C8 100n Film capacitor, 7.2 x 2.5mm Omit if using Morning Glory gain stage. (see build notes)
C9 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C10 47uF Electrolytic capacitor, 6.3mm Voltage reference filter capacitor.
C11 100n MLCC capacitor, X7R Power supply filter capacitor. Added in v1.1.
CX1 100pF MLCC capacitor, NP0/C0G Optional high-frequency feedback capacitor.

CERULEAN AMP OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
CX2 100n Film capacitor, 7.2 x 2.5mm Part of the optional Morning Glory gain stage. (see build notes)
CX3 10uF Electrolytic capacitor, 5mm Part of the optional Morning Glory gain stage. (see build notes)
CX4 2.2uF Electrolytic capacitor, 4mm Part of the optional Morning Glory gain stage. (see build notes)
CX5 OMIT Electrolytic capacitor, 4mm 1uF is used in the King of Tone variant.
D1 1N5817 Schottky diode, DO-41
D2 1N914 Fast-switching diode, DO-35
D3 1N914 Fast-switching diode, DO-35
D4 1N914 Fast-switching diode, DO-35
D5 1N914 Fast-switching diode, DO-35
D6 LED LED, 3mm, red diffused
D7 LED LED, 3mm, red diffused
D8 1N914 Fast-switching diode, DO-35
D9 1N914 Fast-switching diode, DO-35
D10 1N914 Fast-switching diode, DO-35
D11 1N914 Fast-switching diode, DO-35
D12 1N914 Fast-switching diode, DO-35
D13 1N914 Fast-switching diode, DO-35
Q1 2N5457 JFET, N-channel, TO-92 Part of the optional Morning Glory gain stage. (see build notes)
IC1 TL072 Operational amplifier, DIP8
PRES 50k trimmer Trimmer, 10%, 1/4"
HARD SPDT Toggle switch, SPDT, on-off-on Hard clipping (low, high or none)
SOFT SPDT Toggle switch, SPDT, on-off-on Soft clipping (low, high or none)
DRIVE 100kB 16mm right-angle PCB mount pot Linear taper.
TONE 25kB 16mm right-angle PCB mount pot Linear taper.
VOL 100kA 16mm right-angle PCB mount pot Audio (log) 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.

CERULEAN AMP OVERDRIVE 5
BUILD NOTES
Morning Glory Gain Stage
The JHS Morning Glory adds another gain stage to the end of the circuit for more available output
volume. You can choose to build the pedal with this gain stage or without.
To build with the gain stage, omit C8 and include RX1-6, CX2-4 and Q1.
To build without the gain stage, include C8 and omit RX1-6, CX2-4 and Q1.
King of Tone
The Analogman King of Tone is two Bluesbreakers in one box. All of the modifications from the King of
Tone are available as part of this project (soft clipping, hard clipping, and Presence control).
If you use a 1790NS enclosure you could fit two of these side by side. Information on this will be
provided for this at a later date, but as of right now it is outside the scope of the documentation.

SCHEMATIC
1M
3k3
4k7 10k
220k
6k8
1k
6k8
47k
47k
2M2
10n
10n
10n
100n
10n 10n
100n
47pF
TL072P
TL072P
+9V VR
100uF
GND GND
47uF
GND
GND VR
100kB
25kB
100kA
VR
VR
50kB
VR
VR
GND
1uF
100n
68k
1M
2N5457
22k
12k
12k
GND GNDGND
GND
100k
VR
100pF
GND
1N5817
VA
VA
VA
2.2uF
10uF
IN
OUT
R1
R2
R3 R4
R5
R6
R7
R8
R9
R10
RPD
C1
C3
C4 C5
C6 C7
C8
C2
IC1A
2
3
1
IC1B
6
5
7
C9 C10
DRIVE
1
2
3
TONE
1
2
3
VOLUME
1
2
3
84
PRESENCE
1
2
3
CX5
CX2
RX2
RX3
Q1
RX4
RX5
RX6
RX1
D2 D3
D4D5
CX1
D1
SOFT
2
3
1
HARD
2
3 1
CX4
D8 D9
D10D11
D13 D12
CX3
D6
D7
100n
GND
C11
CERULEAN AMP OVERDRIVE 6

CERULEAN AMP OVERDRIVE 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.
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.85, y: +0.66
ø1/4”
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
HARD CLIP SOFT CLIPTONE
GAIN
FOOTSWITCHLED
x: +0.85, y: +0.66
ø1/4”
0 1 2
CM
0 1
INCH

CERULEAN AMP OVERDRIVE 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

CERULEAN AMP OVERDRIVE 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.

CERULEAN AMP OVERDRIVE 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 cannotbe 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
1.1.0 (2020-05-18)
• Changed value of C10 for consistency.
• Slight layout change, relocating D1 to footswitch board.
• Added C11 MLCC capacitor to footswitch board.
1.0.1 (2018-08-14)
Corrected parts list to specify LEDs for D6 and D7. Minor formatting adjustments.
1.0.0 (2018-07-04)
Initial release.