aion GAIA MK.II User manual

GAIA PREAMP DRIVE MK. II 1
PROJECT NAME
GAIA MK. II
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Catalinbread®Galileo
An adaptation of the signature tone of Brian May from Queen, achieved by combining a Rangemaster-
style treble booster with a Vox®AC30 amp.
Overdrive / Amp Emulation 1.0.0 (2020-11-27)
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.87” (bypass board).
BUILD DIFFICULTY
Intermediate

GAIA PREAMP DRIVE MK. II 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 Gaia Preamp Drive is an adaptation of the Catalinbread Galileo, their pedal emulation of treble-
boosted Vox®AC30 tone made famous by Brian May of Queen.
The Galileo is essentially a combination of two other Catalinbread pedals, the Naga Viper (a hot-rodded
silicon Rangemaster treble booster) and the CB30, their take on the AC30. In fact, the first version of
the Galileo was just these two circuits in the same enclosure with separate controls and footswitches for
both circuits.
The second version of the Galileo was a complete redesign, taking the same basic building blocks of a
treble booster + amp-style overdrive, but reducing it down to 3 knobs: treble booster gain (just called
Gain), tonestack treble (just called Tone), and master volume. The amp section’s gain control and bass
knob are internally fixed. This 3-knob Galileo is the version that this project is adapted from.
The original 3-knob Galileo used MPF4393 JFETs, which are no longer produced. Aion FX sells the
original MPF4393 in sets of 5. The PCB also has an extra pad so that surface-mount JFETs can be
used (part number MMBF4393), which are still in production and perform identically to those used in
Catalinbread pedals. See build notes for more details.
The Gaia Mk. II is compatible with the 18V Voltage Doubler / Bypass module if you want to run the
circuit at 18V without an external adapter. The higher voltage provides increased volume and clarity.
USAGE
The Gaia Mk. II has the following controls:
• Gain controls the amount of gain in the treble-booster stage that precedes the amplifier section.
• Tone is equivalent to the treble control of the AC30’s tone stack.
• Volume is the overall output level.

GAIA PREAMP DRIVE MK. II 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 220k Metal film resistor, 1/4W
R2 68k Metal film resistor, 1/4W
R3 10k Metal film resistor, 1/4W
R4 8k2 Metal film resistor, 1/4W
R5 100k Metal film resistor, 1/4W
R6 470k Metal film resistor, 1/4W
R7 680k Metal film resistor, 1/4W
R8 1k Metal film resistor, 1/4W
R9 1k Metal film resistor, 1/4W
R10 1M Metal film resistor, 1/4W
R11 1M Metal film resistor, 1/4W
R12 56k Metal film resistor, 1/4W
R13 470k Metal film resistor, 1/4W
R14 1k Metal film resistor, 1/4W
R15 1k Metal film resistor, 1/4W
R16 1M Metal film resistor, 1/4W
R17 1M Metal film resistor, 1/4W
R18 10k Metal film resistor, 1/4W
R19 100k Metal film resistor, 1/4W
R20 62k Metal film resistor, 1/4W
R21 12k Metal film resistor, 1/4W
R22 1k Metal film resistor, 1/4W
R23 2M2 Metal film resistor, 1/4W
R24 2M2 Metal film resistor, 1/4W
R25 4k7 Metal film resistor, 1/4W
R26 8k2 Metal film resistor, 1/4W
R27 100R Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 4n7 Film capacitor, 7.2 x 2.5mm
C2 47pF MLCC capacitor, NP0/C0G

GAIA PREAMP DRIVE MK. II 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C3 47uF Electrolytic capacitor, 5mm
C4 10n Film capacitor, 7.2 x 2.5mm
C5 100n Film capacitor, 7.2 x 2.5mm
C6 2.2uF Film capacitor, 7.2 x 5mm Can also substitute electrolytic (polarity marked on PCB)
C7 100n Film capacitor, 7.2 x 2.5mm
C8 470pF MLCC capacitor, NP0/C0G
C9 22uF Electrolytic capacitor, 5mm
C10 220n Film capacitor, 7.2 x 2.5mm
C11 47pF MLCC capacitor, NP0/C0G
C12 22n Film capacitor, 7.2 x 2.5mm
C13 22n Film capacitor, 7.2 x 2.5mm
C14 1uF Film capacitor, 7.2 x 3.5mm
C15 1uF Film capacitor, 7.2 x 3.5mm
C16 1n Film capacitor, 7.2 x 2.5mm
C17 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C18 100n MLCC capacitor, X7R Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
Q1 PN2222A BJT transistor, NPN, TO-92 Can also substitute 2N3904.
Q2 MMBF4393 JFET, N-channel, SOT-23 Substitute for MPF4393 (TO-92). See build notes.
Q3 MMBF4393 JFET, N-channel, SOT-23 Substitute for MPF4393 (TO-92). See build notes.
Q4 MMBF4393 JFET, N-channel, SOT-23 Substitute for MPF4393 (TO-92). See build notes.
Q5 MMBF4393 JFET, N-channel, SOT-23 Substitute for MPF4393 (TO-92). See build notes.
Q6 MMBF4393 JFET, N-channel, SOT-23 Substitute for MPF4393 (TO-92). See build notes.
GAIN 5kC 16mm right-angle PCB mount pot
TONE 1MA 16mm right-angle PCB mount pot
VOL. 250kB 16mm right-angle PCB mount pot
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.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

GAIA PREAMP DRIVE MK. II 5
BUILD NOTES
Using SMD JFETs
The MPF4393 JFET is no longer available from the original manufacturer in through-hole format.
This PCB uses a hybrid through-hole/SMD outline for each JFET. An extra “G” (gate) pad is included to
accommodate the MMBF4393 surface-mount version without the need for adapters.
SMD JFETs should be oriented as follows:
All surface-mount JFETs use the same pinout, so this configuration will fit any type that we’re aware
of. However, always check the datasheet if you’re uncertain—they’re difficult to desolder if you make a
mistake.
MPF4393s from Aion FX
We have a large quantity of through-hole MPF4393 and should be able to provide them in hobbyist
quantities for the foreseeable future. They are available in sets of 5. They are manufactured by ON
Semiconductor, the same as those used in the original Catalinbread pedal. They test in the same range
and will perform identically.

SCHEMATIC
GAIA PREAMP DRIVE MK. II 6
GND
2M2
5kC
1MA
250kB
4n7
220k68k
GND
VA
47pF
P2N2222A
10k8k2
GND
47uF
GND
VA
10n
100k
470k
GND
100n
680k
MPF4393
1k
2u2
GND GND
1k
100n
MPF4393
1M 1M
VA
GND
VA
470pF
56k
470k
GND
MPF4393
1k
22uF
GND GND
1k
220n
MPF4393
1M 1M
GND
VA
10k
100k
47pF
VA
22n22n
62k12k
GND
1uF
1k
2M2 2M2
GND
VA
MPF4393
VA
4k7
GND
1uF 8k2
1n
GND
GND
IN
OUT
RPD
GAIN
1
2
3
TONE
1
2
3
VOLUME
1
2
3
C1
R1R2
C2
Q1
R3R4
C3
C4
R5
R6
C5
R7
Q2
R8
C6
R9
C7
Q3
R10 R11
C8
R12
R13
Q4
R14
C9
R15
C10
Q5
R16 R17
R18
R19
C11
C12C13
R20R21
C14
R22
R23 R24
Q6
R25
C15
R26
C16
1N5817
100uF
GND
+9V
100n
VA
100R
D1
C17
C18
R27
GND

GAIA PREAMP DRIVE MK. II 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
TONE
GAIN
FOOTSWITCHLED

GAIA PREAMP DRIVE MK. II 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

GAIA PREAMP DRIVE MK. II 9
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT

GAIA PREAMP DRIVE MK. II 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 (2020-11-27)
Initial release.