aion REFRACTOR User manual

REFRACTOR PROFESSIONAL OVERDRIVE 1
PROJECT NAME
REFRACTOR
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Klon Centaur / KTR
A part-for-part replica of a mythical overdrive effect noted for its high-end tone and price. The Klon
Centaur and its successor, the KTR, remain highly original designs in an industry full of clones and
tweaks to existing circuits.
Overdrive 1.0.3 (2018-11-22)
BUILD DIFFICULTY
Intermediate
This documentation is for the kit version of the project. If you purchased the PCB by itself, please
use the PCB-only version of the documentation instead. The circuit is the same, but the instructions
are completely different due to the specialized parts and assembly methods used in the kit.
IMPORTANT NOTE

REFRACTOR PROFESSIONAL OVERDRIVE 2
TABLE OF CONTENTS
1Project Overview
2Table of Contents
3Introduction
5Packing List
6Packing List (Cont.)
7Tools Needed
8Component Identification
9Hardware Identification
10 Main PCB: Overview
11 Main PCB: Resistors
12 Main PCB: Diodes
13 Main PCB: Sockets & ICs
14 Main PCB: Capacitors (Non-Polarized)
15 Main PCB: Wire Headers
16 Main PCB: Capacitors (Polarized)
17 Footswitch PCB
18 Input/Output PCB
19 Enclosure Layout: Panel Mounts
20 Enclosure Layout: Main & Footswitch PCBs
21 Enclosure Layout: Input/Output PCB
22 Final Testing & Assembly
23 Schematic
24 Full Parts List
25 Troubleshooting Information
26 Support & Resale Terms
27 Legal Information & Document Revisions

REFRACTOR PROFESSIONAL OVERDRIVE 3
INTRODUCTION
If this is your first pedal, welcome to the hobby and thank you for choosing Aion FX. You’ve just joined
a community of over 40,000 people around the world with a passion for building homemade noise
machines using obsolete electronics technologies, and we’re glad to have you!
If you’ve done this before, it’s great to see you again and we’re confident you’ll find this build experience
an enjoyable one.
Aion FX kits are designed to empower anyone to build a high-quality pedal, no matter the skill level.
The pedalbuilding hobby has traditionally had a steep learning curve, but don’t be overwhelmed—we’ve
done all the hard work for you. All you need to do is follow these instructions and you’ll be on your way
to transforming your tone.
There are a few things to go over before you get started.
• You’re going to have to get your hands dirty—there’s no way around it. Nothing here comes
preassembled, and you’ll have to learn the skills to put it all together. This document will walk you
through everything you need, but be prepared to learn a few things along the way.
• This will take time. Plan on about two hours start to finish. It may take even longer if it’s your first
time building. Don’t rush it. If you find yourself getting frustrated or overwhelmed, take a break and
come back in a couple of hours or the next day.
• No direct technical support is offered. There are several DIY forums and Facebook groups with
thousands of members who enjoy troubleshooting and teaching. But please be sensitive to the fact
that the staff at Aion FX is minimal, and every minute spent helping individuals in private is time
that can’t be spent on new project development.
• There is no implied guarantee of a final product. Aion FX provides the ingredients and the recipe,
but you are responsible for putting everything together to make it work. We’ve tried to make the
process as clear and accessible as possible, but it must be expressly stated that purchasing the kit is
not a guarantee that you will end up with a working pedal.
It’s recommended to read through all of the instructions before you start, particularly if you’ve never
built a pedal before. If you familiarize yourself with the entire process ahead of time and you know what
the goal looks like, each step will make more sense.
Now, on to the fun stuff!

REFRACTOR PROFESSIONAL OVERDRIVE 4
PACKING LIST
This is a list of all the parts that are included with the kit, grouped by value. For a list of all the parts
based on their PCB part numbers, please see page 23.
If you find that any parts are missing or damaged, please fill out the Missing Parts form.
Film Capacitors
NAME QTY
2n2 1
3n9 1
27n 1
68n 2
82n 1
100n 2
390n 1
1uF 2
Electrolytic Capacitors
NAME QTY
4.7uF 2
10uF 4
47uF 1
100uF 1
Tantalum Capacitors
NAME QTY
1uF 1
MLCC Capacitors
NAME QTY
390pF (marked “391”) 1
820pF (marked “821”) 1
Resistors
NAME QTY
560R 2
1k 2
1k5 2
1k8 1
2k 1
4k7 2
5k1 1
10k 2
12k 1
15k 2
22k 1
27k 3
47k 1
68k 2
100k 4
392k 1
422k 1
2M 2
Diodes
NAME QTY
1N4001 2
1N4742 1
ICs
NAME QTY
TL072 2
TC1044S 1
8-pin socket 3

REFRACTOR PROFESSIONAL OVERDRIVE 5
PACKING LIST (CONT.)
Potentiometers
NAME QTY
10kB 2
100kB dual 1
Dust cover 2
Knob 3
Mounting nut, potentiometer, 0.44" 3
Lock washer, potentiometer, 0.5" 3
Outer washer, potentiometer, 0.475" 3
Other
NAME QTY
LED bezel 1
LED, blue 1
D9E germanium diode 2
9V battery snap 1
DC jack 1
Input/output jack 2
Mounting nut, jack, 0.54" 4
Outer washer, jack, 0.6" 2
Lock washer, jack, 0.5" (thin) 2
Enclosure 1
Enclosure screws 4
PCB, main circuit 1
PCB, footswitch 1
PCB, input/output/DC 1
Switches
NAME QTY
Slide switch, 4PDT 1
Stomp switch, 3PDT 1
Mounting nut, stomp switch, 0.6" 2
Lock washer, stomp switch, 0.6" 1
Dress nut, stomp switch, 0.77" 1
Wiring
NAME QTY
3-strand wire assembly, 70mm 2
4-strand wire assembly, 108mm 1
3-pin wire assembly header 2
4-pin wire assembly header 1

REFRACTOR PROFESSIONAL OVERDRIVE 6
TOOLS NEEDED
SOLDERING IRON
Temperature-adjustable is
recommended. The optimum
soldering temperature is 700-725º
F (371-385º C) for leaded solder, or
750º F (400º C) for lead-free.
WIRE SNIPPERS
Also called nippers or wire cutters.
The Hakko CHP-170 is the best you
can get for less than $10.
SCREWDRIVER (PHILLIPS)
Used for the enclosure screws. Get a
powered driver if you’ll be building a
lot of pedals!
SOLDER
Preferably 63/37 or 60/40 leaded
solder. Lead-free is more difficult to
use, so if that’s the only type you can
get, it’s best to watch tutorials that
are specific to lead-free solder.
NEEDLE-NOSE PLIERS
These are used for bending leads on
components and other general uses.
Use the smaller type with a tip that’s
approximately 0.05” (1.25mm) wide.
FLAT SCREWDRIVER (SMALL)
This is used for tightening the set
screws on the knobs. The tip should
be no more than 0.1” (2.5mm) wide.
DIGITAL MULTIMETER (DMM)
Most cheap ones in the $10-30 range
are fine for what we’re doing. Make
sure it has audible continuity testing
(i.e. it beeps at the lowest resistance)
and transistor hFE measurement.
FLAT-NOSE PLIERS
Many general-purpose uses, but par-
ticularly tightening the nuts of pots,
switches and jacks. Quicker than
changing out sockets on a ratchet.
RUBBER BAND
Yes, a plain old rubber band. This is
used to tighten the dress nut to avoid
scratching or denting it (which can
happen with metal tools).

REFRACTOR PROFESSIONAL OVERDRIVE 7
COMPONENT IDENTIFICATION
If you’ve never built a pedal before, you’ll need to know what all the components are. These are shown
actual size. (Not all of these types of components may be part of this kit.)
TRIM POTENTIOMETER
FILM CAPACITOR
SILICON DIODE
ZENER DIODE
LED
DC JACKWIRE ASSEMBLY HEADER
LED BEZEL
WIRE ASSEMBLY
ELECTROLYTIC CAPACITOR
IC OR OP-AMP
TANTALUM CAPACITOR
SCHOTTKY DIODE
IC SOCKET SNAP-APART SOCKET
RECTIFIER DIODE
TRANSISTOR OR JFET
Not polarized. Color may
vary by brand and type.
Not polarized. MLCC stands for
“multi-layer ceramic capacitor.”
Some Schottky diodes
also look like this.
Polarized. The positive side
is marked.
Polarized. The negative side
is marked.
Some voltage regulators
also look like this.
It’s recommended to use a
razor blade to separate
these cleanly.
Charge pumps and delay chips
also look like this. They may
have more than 8 legs.
RESISTOR
GERMANIUM DIODE
MLCC
These are very fragile, so be
careful when handling them.

REFRACTOR PROFESSIONAL OVERDRIVE 8
HARDWARE IDENTIFICATION
The hardware comes unassembled, so you’ll need to sort & identify each of the pieces. The diagrams
below are actual size, so you can set them against the printed page to identify them if needed.
I/O JACK
TOGGLE SWITCH
POTENTIOMETER
(SINGLE)
FOOTSWITCH
POTENTIOMETER
(DUAL)
MOUNTING NUT
MOUNTING NUT
MOUNTING NUT
MOUNTING NUT
DRESS NUT
OUTER WASHER
DRESS NUT
OUTER WASHER KNOB
LOCK WASHER
LOCK WASHER
LOCK WASHER
LOCK WASHER
DIAMETER: 0.54” / 13.7mm
DIAMETER: 0.36” / 9.1mm
DIAMETER: 0.44” / 11.2mm DIAMETER: 0.5” / 12.7mm
DIAMETER: 0.6” / 15.2mm
DIAMETER: 0.375” / 9.5mm
DIAMETER: 0.475” / 12mm
DIAMETER: 0.5” / 12.7mm
DIAMETER: 0.4” / 10.1mm
DIAMETER: 0.6” / 15.2mmDIAMETER: 0.77” / 19.6mmDIAMETER: 0.6” / 15.2mm

REFRACTOR PROFESSIONAL OVERDRIVE 9
MAIN PCB: OVERVIEW
Now it’s time to start building!
The first thing you need to do is snap apart the PCB into 3 separate boards and break off the tabs from
each using needle-nose or flat-head pliers. You should be left with this:
The general principle for PCB population is that you work in layers from shortest components (i.e.
lowest-profile) to tallest so that when the PCB is upside-down, everything is making contact with the
work surface and is held in place.
So, you will start by populating the resistors (the lowest-profile components), followed by the diodes,
sockets, film capacitors, and finally the electrolytic capacitors.

REFRACTOR PROFESSIONAL OVERDRIVE 10
MAIN PCB: RESISTORS
PART VALUE
R1 10k
R2 2M
R3 100k
R4 560R
R5 5k1
R6 10k
R7 1k5
R8 1k5
PART VALUE
R9 1k
R10 2k
R11 15k
R12 422k
R13 1k
R15 22k
R16 47k
R17 27k
PART VALUE
R18 12k
R19 15k
R20 392k
R21 1k8
R22 100k
R23 4k7
R24 100k
R25 560R
PART VALUE
R26 68k
R27 68k
R28 100k
R29 27k
R30 27k
RPD 2M
LEDR 4k7
Using the parts list above, populate the resistors by pushing them through the holes and bending the
leads outward at an angle to hold them in place. Resistors are not polarized, so they will work in any
direction. Turn the board upside-down to keep the components held in place while you solder.
You’ll use this same technique for most of the other components as well.
Don’t try to do all of the resistors at once. You’ll want to stop periodically flip the board and solder
everything, then cut the leads using the wire snippers to make room for more. Generally you don’t want
to do more than 15 to 20 resistors at a time or the bottom of the board will get too crowded.
If this is your first time soldering, watch tutorial videos on YouTube and make sure you get it down
before you begin. You don’t want to practice or experiment on this board!

REFRACTOR PROFESSIONAL OVERDRIVE 11
MAIN PCB: DIODES
PART VALUE
D1 D9E
D2 D9E
D3 1N4001
D4 1N4001
Z1 1N4742A
Next, you’ll populate the diodes. Diodes are polarized, so make sure to identify the polarity band (which
indicates the “cathode”, or negative side) and match the band to the footprint on the PCB.
Germanium diodes will sometimes have more than one band. In these cases, the larger or wider band is
the one that indicates the cathode side.
Precautions with germanium diodes
Germanium diodes are fragile and require more care than the other components. Make sure to observe
the following precautions when working with them.
• To prevent stress on the glass body of the diode, when bending the leads, use needle-nose pliers or
tweezers to clamp the lead as close to the body as possible while you bend it down. The bend should
be about 0.05–0.08” from the body of the diode, so make sure to use pliers that are narrow enough.
• Old-stock diodes can sometimes develop corrosion on the leads, making them difficult to solder. It’s
recommended to use sandpaper or a small file to gently rough up the leads where they will make
contact with the solder. This will make adhesion much easier.
• Be quick when soldering. Germanium diodes can easily be damaged by overheating. Contact with
the soldering iron should be limited to 1-2 seconds maximum. If you don’t have a good solder joint,
wait a minute or two for it to cool before trying again.
The germanium diodes included with this kit have been individually tested and verified as working.
Unless they arrive damaged, free replacements will not be offered, so please be careful!

REFRACTOR PROFESSIONAL OVERDRIVE 12
MAIN PCB: SOCKETS & ICS
Next up are the sockets. You can’t bend the leads of the sockets like you can with the other components,
so they won’t stay in on their own until they are soldered.
Again, it’s much easier to do all of these at once with gravity holding them in place for you, so you’ll want
do them before you do any of the taller components.
Installing the ICs
Don’t insert the ICs into the sockets just yet. We will do this in a later step, after we’ve finished soldering
the tallest components (the polarized capacitors). This information is just listed here for reference.
The legs of each IC are bent outward slightly during manufacturing, so they’ll need to be bent back
inward before they can be inserted into the sockets.
It’s easiest to do this by laying the IC legs against the table and bending the body itself so all four legs on
the side are straightened out at once. Then, flip it and do the other side.
ICs may have two different orientation marks: either a dot in the upper-left or a half-circle notch in the
middle of the top side. Some ICs have both marks. This shows which way the IC should be rotated when
inserting it into a socket (the socket also has a half-circle notch).
PART VALUE
IC1 TL072
IC2 TL072
IC3 TC1044S

REFRACTOR PROFESSIONAL OVERDRIVE 13
MAIN PCB: CAPACITORS (NON-POLARIZED)
After the sockets come the box film and MLCC capacitors. These are all several different heights, but
there aren’t as many, so just do them all at once. Bend the leads at an angle to hold them in place.
MLCCs and box capacitors are not polarized, so they will work in any direction, but to keep things neat,
it’s best to put them all facing the same way.
PART VALUE
C1 100n
C3 100n
C4 68n
C5 68n
C6 390n
C7 82n
C8 390pF MLCC
C9 1uF
C10 1uF
C11 2n2
C12 27n
C13 820pF MLCC
C14 3n9

REFRACTOR PROFESSIONAL OVERDRIVE 14
MAIN PCB: WIRE HEADERS
Install the two 3-pin headers (wire connectors) as shown above. These have a polarity pin, so as long
as they are pressed all the way down, there’s only one possible way to install them. They do fit pretty
tightly in the holes, though, so press firmly.
There’s also a 4-pin header on the I/O board that we will do in a later step.

REFRACTOR PROFESSIONAL OVERDRIVE 15
MAIN PCB: CAPACITORS (POLARIZED)
Populate the electrolytic capacitors. These are the tallest components so we save them for last. They are
polarized (i.e. they will only work in one direction), so note the vertical mark that indicates the negative
side. The longer leg is positive and fits in the square pad.
Next, populate the yellow tantalum capacitor (C16). Be very careful with this: unlike electrolytic
capacitors, tantalum capacitors have the “+” (positive) side marked instead of the negative. Since
tantalum capacitors aren’t commonplace in guitar pedals, many people instinctively reverse them, and
as a result, their build has issues. Like electrolytics, the longer leg still goes in the square pad.
These are the last of the on-board components. Now is the time to go back to page 13 and insert the ICs
into the sockets.
PART VALUE
C2 4.7uF
C15 4.7uF
C16 1uF tantalum
C17 100uF
C18 47uF
C19 10uF
C20 10uF
C21 10uF
C22 10uF

REFRACTOR PROFESSIONAL OVERDRIVE 16
FOOTSWITCH PCB
Next, it’s time to finish up the footswitch board. You should have done most of the on-board components
on this board in a previous step, but if not, go back and do those.
It’s easiest to start with the slide switch. Fit it in as shown in the diagram above, with the slide lever
facing to the right. Be careful—the pads are small. Make sure you don’t accidentally “bridge” two pads
together when soldering or you will have issues with the bypass.
The wires are next. There will be one longer assembly with 4 wires and two shorter ones with 3
wires. The longer one goes in the middle and the shorter ones go on the left and right sides. The wire
assemblies should then be soldered to the footswitch board as shown.
Once all three wire assemblies are soldered, set the footswitch PCB aside. We’ll solder the actual
footswitch and LED in a later step.
PARTS
Slide switch, 4PDT
3-strand wire assembly (2)
4-strand wire assembly
STEP 3
Then, solder the wires from the top.
This is the trickiest part of the whole
build. You want to solder the pads
without touching the iron to the
wires themselves and risking burning
through the insulation. It helps to
use a sharp or narrow tip on the
soldering iron.
STEP 2
Next, bend the wires back upward
and fit the ends of the wires into the
solder pads.
On the top side of the PCB, bend the
exposed wires backward so it holds
the wire in place. Pull the header
back up through the slot partway.
STEP 1
First, thread the wire through the
strain-relief slots, with the blue side
facing outward.
For now, pull it through as far as it
can go.
BLUE
MARKING

REFRACTOR PROFESSIONAL OVERDRIVE 17
INPUT/OUTPUT PCB
Almost done! Get the two input/output jacks, the DC jack and the wire header and snap them in place.
The PCB is designed for them to fit securely, so you can do them all at once before flipping and soldering.
After you’ve soldered everything, make sure to snip the leads on the I/O jacks as close as possible to
the PCB. There’s not a lot of clearance between the bottom of this board and the top of the main PCB
once everything is in place, and you don’t want the pins to short against anything on accident.
Next, we’ll hook up the 9V battery connector. This is optional. The first versions of the Centaur had
battery snaps, but it was removed early on because the effect eats them pretty quickly. A battery snap
has been provided with the kit, but it’s still recommended to only power this with an external supply.
PARTS
Input & output jacks
DC jack
Wire header
9V battery snap
STEP 1
Thread the battery snap through the strain-relief
hole twice so it forms a single loop.
STEP 2
Bend the exposed wires back down and solder them
into the pads. Red is positive (+), black is negative (-).
After soldering, pull it tight.
For even more strain relief, you can thread the snap
through the loop to form a knot. (not shown)

REFRACTOR PROFESSIONAL OVERDRIVE 18
ENCLOSURE LAYOUT: PANEL MOUNTS
Attach the hardware to the enclosure as shown. (The I/O board is done in a later step.)
125B
100kB DUAL 10kB
10kB
FOOTSWITCH
BEZEL
& LED
MOUNTING NUT
MOUNTING NUT
DRESS NUT
LOCK WASHER
MOUNTING NUT
LOCK RING
MOUNTING NUT
OUTER WASHER
LOCK WASHER
DUST CAP
FOOTSWITCH
BEZEL & LED
The dress nut fits over the top of the mounting nut and is for aesthetic
purposes only. Wrap a rubber band around it to use as a grip when tightening.
Do not use metal tools on it or you run the risk of scratching or denting it.
You’ll need to hold the bezel in place when
tightening the nut. Be aware that the bezel is fairly
sharp. Try using a rubber band for grip instead of
just pressing your finger against the bottom.
The dust cap is not used on
the dual potentiometer.
The LED will just
sit loosely inside
the bezel for now.
POTENTIOMETERS
Volume: 10kB
Drive: 100kB dual
Tone: 10kB

REFRACTOR PROFESSIONAL OVERDRIVE 19
ENCLOSURE LAYOUT: MAIN & FOOTSWITCH PCBS
A note about the dual-gang potentiometer
The upper pads for the dual-gang gain potentiometer appear to be
cut in half. This is intentional. It’s called a plated half-hole or castellated
hole, and it’s used so that the PCB can lay flat across the pots instead of
angling upward for the dual pot.
Solder it like you would if they were normal pads, but bend the top pins
of the pot forward slightly so they make contact with the inside edges of
the half-holes, as shown in the diagram to the right.
Why solder everything inside the enclosure before testing it?
“Rock it before you box it” is conventional wisdom in pedalbuilding, and you’ll often hear it
recommended that builders should test the circuit before putting everything inside the enclosure.
However, Aion FX projects are designed to be extremely easy to remove from the enclosure for
troubleshooting, with no desoldering required—so with these kits, it’s actually much easier to “box it
before you rock it”.
If you’ve read the documentation carefully and followed all the instructions, there’s a good chance you
will get it right the first time!
125B
After all the components are affixed to the enclosure as
shown on the previous page, place the main PCB on top of the
potentiometers as in the diagram to the left.
You may need to adjust the position of the potentiometers
slightly if they are not aligned straight.
Once all of the pins are through and the PCB is laying flat, solder
each of the pins from the top, being careful not to touch any of
the surrounding components with the soldering iron.
After you’ve finished soldering the pots, clip the leads as close
as you can to the main PCB. This is more important with the
two uppermost pots because the input/output PCB overlaps
them and you need to avoid any of the components shorting.
Next, do the same thing with the footswitch board—the 3PDT
footswitch and the LED.
Before soldering, double-check to make sure the flat side of the
LED is facing to the right, as shown in the diagram, and that the
short leg is coming through the pad on the right. It won’t work if
it’s turned the other way.

REFRACTOR PROFESSIONAL OVERDRIVE 20
ENCLOSURE LAYOUT: INPUT/OUTPUT PCB
Affix the input/output PCB to the north-facing panel of the enclosure as shown.
Note the use of two mounting nuts on each of the jacks, one inside and one outside. The inner nut acts as
a spacer to set the DC jack flush with the outside of the enclosure. The inner nuts should be threaded as
far down as they can go.
125B
MOUNTING NUT
LOCK WASHER
OUTER WASHER
MOUNTING NUT