aion GAIA MK. I User manual

GAIA PREAMP DRIVE MK. I 1
PROJECT NAME
GAIA MK. I
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Catalinbread®CB30
An adaptation of the Vox®AC30, a legendary British amplifier responsible for the signature guitar tones
of the 60s and 70s. It uses cascaded mu-amp stages in place of tubes for amp-like tone in a small box.
Overdrive / Amp Emulation 1.0.0 (2021-05-28)
Actual size is 2.3” x 2.42” (main board) and 1.78” x 0.87” (bypass board).
BUILD DIFFICULTY
Intermediate
This documentation is for the Mk. I version of the project. There is also a Mk. II version, based on
the Galileo. While the name is similar, the circuit and part numbering are different. Please be sure
your PCB is labeled “Gaia Mk. I” before proceeding with this build document.
IMPORTANT NOTE

GAIA PREAMP DRIVE MK. I 2
TABLE OF CONTENTS
1Project Overview 8Drill Template
2Introduction & Usage 9Enclosure Layout
3-5 Parts List 10 Wiring Diagram
6Build Notes 11 Licensing
7Schematic 11 Document Revisions
INTRODUCTION
The Gaia Preamp Drive Mk. I is an adaptation of the Catalinbread CB30, their pedal emulation of a Vox®
AC30 amplifier.
The CB30 was originally released in 2011. Curiously, there were two different versions, although there’s
no official record from Catalinbread of a V1 and V2. Aion FX traced a version with eight JFETs in 2021,
and the PCB was dated 2011. However, the Freestompboxes.org community traced one during the first
month it was released (June 2011) and the photos show a completely different PCB layout and a circuit
with only five JFETs.
You can read more about this in the tracing journal post, including theories on why there was a
redesign—but it’s sufficient to say that anyone building a CB30 DIY clone in the past ten years was not
hearing the improved version.
The original CB30 used 2N5457 JFETs, which are no longer available in through-hole format. Extra pads
have been provided if you want to use surface-mount JFETs (part number MMBF5457), which perform
identically to those used in Catalinbread pedals. Aion FX also offers pre-soldered MMBF5457s on
adapter boards if you find surface-mount parts intimidating. See build notes for more details.
In 2012, the CB30 was incorporated into the Galileo, a dual pedal containing a Rangemaster-derived
Naga Viper treble booster in the same enclosure, emulating Brian May’s treble-boosted AC30 guitar
tone. In 2014, the second version of the Galileo was released, this time a single pedal that internally
contained the Naga Viper and a redesigned CB30 using MPF4393 JFETs, but with only three knobs and
one footswitch. This is available from Aion FX as the Gaia Mk. II.
The Gaia Mk. I can be run at 18V for increased volume and clarity, but it is not compatible with the 18V
Voltage Doubler / Bypass module due to the larger format of the PCB.
USAGE
The Gaia Mk. I has the following controls:
• Gain controls the amount of gain in the first amplifier stage.
• Bass and Treble form a two-band tone stack arranged the same as the original Vox amplifiers.
• Volume is the overall output level.

GAIA PREAMP DRIVE MK. I 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 100k Metal film resistor, 1/4W
R2 470k Metal film resistor, 1/4W
R3 680k Metal film resistor, 1/4W
R4 390R Metal film resistor, 1/4W
R5 1M Metal film resistor, 1/4W
R6 1M Metal film resistor, 1/4W
R7 100k Metal film resistor, 1/4W
R8 100k Metal film resistor, 1/4W
R9 470k Metal film resistor, 1/4W
R10 2M2 Metal film resistor, 1/4W
R11 390R Metal film resistor, 1/4W
R12 1M Metal film resistor, 1/4W
R13 1M Metal film resistor, 1/4W
R14 100k Metal film resistor, 1/4W
R15 12k Metal film resistor, 1/4W
R16 470k Metal film resistor, 1/4W
R17 470k Metal film resistor, 1/4W
R18 2M2 Metal film resistor, 1/4W
R19 390R Metal film resistor, 1/4W
R20 1M Metal film resistor, 1/4W
R21 1M Metal film resistor, 1/4W
R22 470k Metal film resistor, 1/4W
R23 470k Metal film resistor, 1/4W
R24 3M3 Metal film resistor, 1/4W
R25 1k Metal film resistor, 1/4W
R26 1M Metal film resistor, 1/4W
R27 1M Metal film resistor, 1/4W
R28 100R Metal film resistor, 1/4W
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 to change LED brightness.

GAIA PREAMP DRIVE MK. I 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C1 100n Film capacitor, 7.2 x 2.5mm
C2 470pF MLCC capacitor, NP0/C0G
C3 2.2uF Electrolytic capacitor, 4mm
C4 47n Film capacitor, 7.2 x 2.5mm
C5 470pF MLCC capacitor, NP0/C0G
C6 470pF MLCC capacitor, NP0/C0G
C7 47pF MLCC capacitor, NP0/C0G
C8 680n Film capacitor, 7.2 x 4.5mm
C9 2.2uF Electrolytic capacitor, 4mm
C10 10uF Electrolytic capacitor, 5mm
C11 2.2uF Electrolytic capacitor, 4mm
C12 470pF MLCC capacitor, NP0/C0G
C13 47pF MLCC capacitor, NP0/C0G
C14 22n Film capacitor, 7.2 x 2.5mm
C15 22n Film capacitor, 7.2 x 2.5mm
C16 1uF Film capacitor, 7.2 x 3.5mm
C17 47uF Electrolytic capacitor, 5mm
C18 2.2uF Electrolytic capacitor, 4mm
C19 1uF Electrolytic capacitor, 4mm
C20 2n2 Film capacitor, 7.2 x 2.5mm
C21 1uF Film capacitor, 7.2 x 3.5mm
C22 22uF Electrolytic capacitor, 5mm
C23 2.2uF Electrolytic capacitor, 4mm
C24 2.2uF Electrolytic capacitor, 4mm
C25 1n Film capacitor, 7.2 x 2.5mm
C26 2.2uF Film capacitor, 7.2 x 5mm
C27 100uF Electrolytic capacitor, 6.3mm
C28 100n MLCC capacitor, X7R
D1 1N5817 Schottky diode, DO-41
Q1 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.
Q2 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.
Q3 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.
Q4 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.
Q5 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.
Q6 MMBF5457 JFET, N-channel, TO-92 Substitute for 2N5457 (TO-92). See build notes.

GAIA PREAMP DRIVE MK. I 5
PARTS LIST, CONT.
PART VALUE TYPE NOTES
Q7 MMBF5457 JFET, N-channel, SOT-23 Substitute for 2N5457 (TO-92). See build notes.
Q8 MMBF5457 JFET, N-channel, SOT-23 Substitute for 2N5457 (TO-92). See build notes.
GAIN 1MB 16mm right-angle PCB mount pot
BASS 1MA 16mm right-angle PCB mount pot
TREBLE 1MA 16mm right-angle PCB mount pot
VOL. 100kA 16mm right-angle PCB mount pot
IN 1/4" mono 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. I 6
BUILD NOTES
Using SMD JFETs
The 2N5457 JFET is no longer available 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 surface-mount devices
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.
Using through-hole adapters
If you’re not confident in your ability to work with surface-mount parts, Aion FX offers 2N5457
(MMBF5457) JFETs that come pre-soldered to adapters for use in through-hole designs. These are from
the same manufacturer as those used in the original Catalinbread pedals and will perform identically.
Using old-stock JFETs
JFETs are an odd category of component because their manufacturing process is highly inconsistent.
The datasheet for a given part number will usually show an enormous range for crucial specifications
such as VGS(off) and IDSS.
However, in practice, parts from the same manufacturer are usually much tighter in specification. So
while the 2N5457 has a VGS(off) range of -0.5V to -6.0V, devices from ON Semiconductor (Fairchild) will
usually be between -1V and -2V. This is the brand of JFETs used by Catalinbread in this pedal.
This means that the part number itself is not usually enough to go by if you’re trying to replicate a circuit
that uses JFETs in certain types of applications, notably when they’re used for overdrive.
So while the 2N5457 is sometimes available from manufacturers such as Central Semiconductor or
InterFET, the ones we’ve tested have been very far outside the ON Semi range and will perform very
differently in this circuit. Therefore, it is not recommended to use 5457 JFETs from any manufacturer
except ON Semiconductor—although it makes no difference whether it’s an old-stock through-hole
type or the current-production MMBF5457 SMD type.
Conversely, if you find a different type of JFET that measures in the -1V to -2V range for VGS(off), it
should work just as well as the 2N5457.

SCHEMATIC
GAIA PREAMP DRIVE MK. I 7
GND
2M2
1N5817
100uF
1MB
1MA
GND
100kA
+9V
100n
VA
100n
100k
470k 680k
2N5457
470pF
GND
390R
2.2uF
GND GND
2N5457
47n
1M 1M
VA
GND
VA
470pF
VA
470pF
47pF
100k
GND
680n
100k
470k 2M2
2N5457
GND
390R
10uF
GND GND
2N5457
1M 1M
VA
GND
VA
2.2uF
2.2uF 470pF
VA
100k
47pF
22n
22n
1MA
GND
470k
1uF
470k 2M2
2N5457
GND
390R
47uF
GND GND
2N5457
1M 1M
VA
GND
VA
2.2uF
1uF 2n2
VA
470k
1uF
470k 3M3
2N5457
GND
1k
22uF
GND GND
2N5457
1M 1M
VA
GND
VA
2.2uF
2.2uF 1n
VA
2u2
GND
100R
12k
GND
IN OUT
RPD
D1
C27
GAIN
1
2
3
TREBLE
1
2
3
VOLUME
1
2
3
C28
C1
R1
R2 R3
Q1
C2
R4
C3
Q2
C4
R5 R6
C5
C6
C7
R7
C8
R8
R9 R10
Q3
R11
C10
Q4
R12 R13
C9
C11 C12
R14
C13
C14
C15
1
2
3
BASS
R16
C16
R17 R18
Q5
R19
C17
Q6
R20 R21
C18
C19 C20
R22
C21
R23 R24
Q7
R25
C22
Q8
R26 R27
C23
C24 C25
C26
R28
R15
GND

GAIA PREAMP DRIVE MK. I 8
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
ø3/8” ø1/2”
0.385”
0.625” 0.625”
x: -0.65, y: +1.71 x: +0.65, y: +1.71
ø9/32” ø9/32”
x: -0.65, y: +0.41
ø9/32”
x: +0.65, y: +0.41
ø9/32”
x: 0, y: -1.775
ø15/32”
x: -0.775, y: -1.775
ø5/16”
CENTER (0,0)
ø3/8”
125B
OUT
BASS TREBLE
VOLUME GAIN
FOOTSWITCHLED
DC IN

GAIA PREAMP DRIVE MK. I 9
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

GAIA PREAMP DRIVE MK. I 10
WIRING DIAGRAM
125B
IN +VGND NC NC OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT

GAIA PREAMP DRIVE MK. I 11
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 (2021-05-28)
Initial release.