aion Apollo Mk I User manual

APOLLO PREAMP DRIVE MK. I 1
PROJECT NAME
APOLLO MK. I
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Catalinbread®WIIO
An adaptation of the Hiwatt amplifier used by Pete Townshend of The Who during their “Live at Leeds”
performance from 1970.
Overdrive / Amp Emulation 1.0.0 (2021-02-19)
Actual size is 2.3” x 1.86” (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 RAH. While the names are similar, the circuit and part numbering are different. Please be sure
your PCB is labeled “Apollo Mk. I” before proceeding with this build document.
IMPORTANT NOTE

APOLLO PREAMP DRIVE MK. I 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 Apollo Preamp Drive Mk. I is an adaptation of the Catalinbread WIIO, based on the Hiwatt
amplifiers used by Pete Townshend of The Who, particularly their Live at Leeds show from February 14,
1970. (The artwork for the original pedal makes it obvious that “WIIO” is intended to resemble “WHO”.)
The WIIO was originally released in 2009 as a limited run of 100. The limited availability caused a huge
debacle as people from gear forums bought up all the preorders and flipped them for profit, capitalizing
on Catalinbread’s favored status among gear aficionados.
Catalinbread was not happy with the way the circuit turned out, so before releasing the non-limited
version, they overhauled the circuit to reduce the gain and tweak the EQ so it was more versatile as an
amp platform. Most people agree that the second version is superior, but the hype surrounding the first
version has given it a lasting reputation.
The WIIO was succeeded by the RAH, which is largely the same circuit but with a midrange knob added,
and the circuit re-voiced for Led Zeppelin’s famous show at the Royal Albert Hall. (They even referred
to the RAH as the “Royal Albert Hall Edition of the WIIO” in the manual.) The WIIO was discontinued
shortly after the release of the RAH.
The Apollo Mk. I is a direct adaptation of the V2 WIIO (non-limited version). The only modification is the
addition of a trimmer that makes a feedback resistor variable, allowing adjustments to the gain, tone
and feel of the circuit. The RAH is also available from Aion FX as the Apollo Mk. II.
USAGE
The Apollo Mk. I has the following controls:
• Gain controls the amount of gain coming out of the first amplifier stage.
• Bass and Treble form a 2-band tone stack adapted from the original amplifier.
• Master is the overall output level.
• Feedback (internal trimmer) controls the global feedback from the third stage back to the first. Set
it just past the halfway point for the stock circuit, and then adjust it to taste.

APOLLO 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 10M Metal film resistor, 1/4W
R2 3k3 Metal film resistor, 1/4W
R3 3k3 Metal film resistor, 1/4W
R4 1k Metal film resistor, 1/4W
R5 12k Metal film resistor, 1/4W
R6 10M Metal film resistor, 1/4W
R7 3k3 Metal film resistor, 1/4W
R8 3k3 Metal film resistor, 1/4W
R9 100k Metal film resistor, 1/4W
R10 10k Metal film resistor, 1/4W
R11 10M Metal film resistor, 1/4W
R12 3k3 Metal film resistor, 1/4W
R13 3k3 Metal film resistor, 1/4W
R14 130R Metal film resistor, 1/4W
R15 47k Metal film resistor, 1/4W
R16 12k Metal film resistor, 1/4W
R17 12k Metal film resistor, 1/4W
R18 62k Metal film resistor, 1/4W
R19 82k Metal film resistor, 1/4W
R20 100R Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W
C1 270pF MLCC capacitor, NP0/C0G
C2 100n Film capacitor, 7.2 x 2.5mm
C3 100uF Electrolytic capacitor, 6.3mm
C4 100n Film capacitor, 7.2 x 2.5mm
C5 47n Film capacitor, 7.2 x 2.5mm
C6 100uF Electrolytic capacitor, 6.3mm
C7 4.7uF Electrolytic capacitor, 4mm
C8 4n7 Film capacitor, 7.2 x 2.5mm

APOLLO PREAMP DRIVE MK. I 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C9 10n Film capacitor, 7.2 x 2.5mm
C10 10n Film capacitor, 7.2 x 2.5mm
C11 470pF MLCC capacitor, NP0/C0G
C12 100n Film capacitor, 7.2 x 2.5mm
C13 100uF Electrolytic capacitor, 6.3mm
C14 470n Film capacitor, 7.2 x 3mm
C15 10uF Electrolytic capacitor, 5mm
C16 2n2 Film capacitor, 7.2 x 2.5mm
C17 2n2 Film capacitor, 7.2 x 2.5mm
C18 47uF Electrolytic capacitor, 5mm
C19 100uF Electrolytic capacitor, 6.3mm
C20 100n MLCC capacitor, X7R
D1 1N5817 Schottky diode, DO-41
Z1 1N4739A Zener diode, 9V, DO-41
Z2 1N4739A Zener diode, 9V, DO-41
Z3 1N4739A Zener diode, 9V, DO-41
Q1 BS170 MOSFET, N-channel, TO-92
Q2 BS170 MOSFET, N-channel, TO-92
Q3 BS170 MOSFET, N-channel, TO-92
GAIN 500kA 16mm right-angle PCB mount pot
BASS 500kA 16mm right-angle PCB mount pot
TREBLE 500kB 16mm right-angle PCB mount pot
MSTR. 100kA 16mm right-angle PCB mount pot
FDBK. 250k trimmer Trimmer, 10%, 1/4" See build notes.
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.

APOLLO PREAMP DRIVE MK. I 5
BUILD NOTES
Setting feedback trimmer
The WIIO circuit contains a global feedback loop similar to the amplifier it’s based on. A 200k resistor
and 470n capacitor send the output from the third stage back to the point just after the gain control
between the first and second stage, which reduces the gain, cuts some of the top end, and makes it feel
more “amp-like”.
The Apollo Mk. I adds a trimmer in series with the feedback resistor, allowing the feedback to be varied
to taste. Global feedback does several things at once with the gain, EQ and compression
The stock position is between 1-2:00 on the trimmer and this should be the starting point for any builds.
From there, adjust it up or down and see if you like what it does.
If you want to omit this control, jumper the outer pins of the trimmer and use 200k for R15.

SCHEMATIC
APOLLO PREAMP DRIVE MK. I 6
GND
2M2
1N5817
100uF
500kA
500kA
GND
500kB
100kA
+9V
100n
VA
270pF
100n
GND
10M
100R 62k
82k
47uF
GND GND
VB
VB
1N4739A
BS170
3k3
VA
3k3
1k
GND
GND
100uF
100n
12k
GND
47n
10M
1N4739A
BS170
3k3
100uF
GND
GND
3k3
VB
VA
4u7
100k
4n7
10n
GND
GND
10k
10n
GND
470pF
100n
10M
VB
1N4739A
BS170
3k3
VA
3k3
130R
GND
GND
100uF
10uF
12k
2n2 2n2
12k
47k
470n 250k
GND GND
GND
IN OUT
RPD
D1
C19
GAIN
1
2
3
BASS
1
2
3
TREBLE
1
2
3
MASTER
1
2
3
C20
C1
C2
R1
R20 R18
R19
C18
Z1
Q1
R2R3
R4
C3
C4
R5
C5
R6
Z2
Q2
R7
C6
R8
C7
R9
C8
C9
R10
C10
C11
C12
R11
Z3
Q3
R12R13
R14
C13
C15
R16
C16 C17
R17
R15
C14
FEEDBACK
1
2
3
GND

APOLLO PREAMP DRIVE MK. I 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: -0.65, y: +0.41
ø9/32”
x: 0.65, y: +0.41
ø9/32”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
MASTER GAIN
BASS TREBLE
FOOTSWITCHLED

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

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

APOLLO PREAMP DRIVE MK. I 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 (2021-02-19)
Initial release.