aion XENOTRON User manual

XENOTRON MODULATION MACHINE 1
PROJECT NAME
XENOTRON
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Lovetone ? Flange With No Name
A flanger, chorus, tremolo and everything in between, with synth-like controls, regeneration and self-
oscillation for unique and otherworldly sounds.
Tremolo / flanger / modulation 1.0.0 (2023-05-20)
BUILD DIFFICULTY
Expert
Actual size is 5.48” x 2.61” (main board), 5.17” x 0.68” (bypass board),
and 2.35” x 1.20” (BBD daughterboard).

XENOTRON MODULATION MACHINE 2
TABLE OF CONTENTS
1Project Overview 19-20 BBD Sub-Board Assembly
2Warning / Disclaimer 21-23 Schematic
3Introduction 24 PCB Diagram (reverse side)
4Circuit Design Notes 25-26 Drill Template
5-6 Usage 27 Enclosure Layout
7-12 Parts List 28 Wiring Diagram
13 BBD Biasing 29 Troubleshooting Checklist
15-18 Build Notes 30 Licensing & Document Revisions
WARNING / DISCLAIMER
The Xenotron is an expert-level circuit and it takes experience and attention to detail in order to build
it successfully. Please read all of the build documentation to familiarize yourself with every aspect of
the project before you begin. You’re much more likely to have a successful journey if you study the map
carefully beforehand.
Here are a few warnings and precautions to keep in mind before you start:
It’s complex. If you’ve never built a guitar pedal before, this shouldn’t be your first. Or your fifth, or even
your tenth. It has 200 components that are spread across four PCBs and mounted to both sides of each
board. There are a lot of wires. It uses entire categories of components such as LDRs and transformers
not often seen in beginner or intermediate circuits, and it requires fine-tuning for proper operation.
It will take awhile. Expect four to eight hours from start to finish. Double-check all component values
before soldering. One easy mistake—for example, using a 100k resistor instead of 10k—may cost hours
of troubleshooting later.
You’ve got to build it as intended. Everything is designed to fit together in a very particular way. If you
don’t want to use the specified enclosure size and control layout, this probably isn’t the right version of
the circuit for you, and there are other adaptations that might be better choices.
It’s not cheap. Components will be well over USD$125 when ordering from reputable suppliers like
Mouser. The parts are all fairly commonplace and easy to source, but it still may be tempting to cut
costs wherever you can. Just keep in mind that a single fake or low-quality part may be the difference
between a successful build and something that ends up in the scrap pile.
We do not offer direct technical support. If there’s anything we can do to improve the clarity of this
build document, or if you notice any errors, we’re happy to hear suggestions. But our role is to design
projects and sell PCBs and components. It’s up to you to turn these into a working pedal. The staff at
Aion FX is minimal, and time spent helping individuals in private is time away from new projects.
With that out of the way: it is an incredibly rewarding build and there’s nothing else quite like it. Just
take your time and go slowly. All the information you need can be found either in this document or in the
original user’s manual, but it’s up to you to read and understand it.

XENOTRON MODULATION MACHINE 3
INTRODUCTION
The Xenotron Modulation Machine is an adaptation of Lovetone’s legendary “?” Flange With No Name,
probably the most well-known of Lovetone’s lineup, and particularly notable for its complexity both
inside and outside. It was the last of the Lovetone effects to be designed, released in early 2000 shortly
before the company ramped down production. As a result, it’s also the rarest of their effects.
The “?” was called a flanger, but this is just a simplification for lack of a more accurate term. The basic
premise is that it has two primary modulation functions: Space (optical tremolo) and Time (BBD-driven
flange, chorus, doubling, and pseudo-phasing). These can either be used in stereo with separate outputs
for each type of modulation, or summed to mono for a variety of hybrid tones from the two types of
modulation working in tandem.
But the real magic is in the array of knobs and added features. The “Action” (mix) and “Reaction”
(regeneration) controls work with in-phase and out-of-phase copies of the signal, meaning they can
either add or subtract from the signal in their respective areas. Along with this, the delay path has an
optional effects loop for external effects. Together with the CV input and external triggering, it creates
the possibility of sounds that are utterly without comparison in the world of guitar effects.
Also interesting is the design philosophy. If you look at the schematic, the only ICs in use are two for the
LFO and two for the delay section (a BBD and clock), which is really the bare minimum. The rest is driven
by transistors and JFETs, 17 in total—almost as though the designer, Dan Coggins, challenged himself
to do it the hard way without the convenience of op-amps. (Whatever the case, Dan said this was the
design that pushed him over the edge and caused him to quit Lovetone shortly afterward.)
The Xenotron is a faithful recreation of the Flange With No Name, with all the features of the original
in a much smaller package. We’ve done the hard work to make a clean and efficient layout that is as
straightforward to build as it could possibly be, and written this extensive 30-page build document—but
even still, it’s a challenging project and not for the faint of heart.
Due to the complexity of operation, we’ve made the effort to recreate the original Lovetone user manual
as a separate document, and the controls are only described briefly in this main build document. Keep
the manual handy when using it, because if you don’t know how it works then there’s a good chance it
will sound broken the first time you plug it in!
We have also created an Interactive BOM tool for this project to help with the build process.
Components are grouped by value, and you can click any component to see which other parts have the
same value and where they’re located. (Chrome-based browsers only)
Special thanks to Ian (LaceSensor / Gigahearts FX), the DIY community’s resident Lovetone expert, for
help verifying the Xenotron prototype against an original Flange With No Name for accuracy.

XENOTRON MODULATION MACHINE 4
CIRCUIT DESIGN NOTES
When designing the Xenotron, we started with an ambitious idea: what if we could fit the full circuit
with all of its features in a 1590XX enclosure, all using the same components as the original unit? Some
past DIY implementations used larger enclosures, while others eliminated features so it would fit.
But with a whole lot of planning, some creative space-saving solutions, and several revisions, we made it
work. It ended up being by far the most challenging and time-consuming layout we’ve ever done, but also
the one we’re most proud of.
We don’t have a lot of design notes on this one because we didn’t really change anything from the
original design or add anything new like we’ve done with the other Lovetone projects. However, here are
some high-level things to be aware of that are different than most other pedals.
Bypass
The original Flange With No Name does not have a master bypass. The “Space” footswitch cancels the
LED modulation, which essentially reduces the tremolo depth to zero. The “Time” footswitch makes it
so the “Time” jack output is taken from the tremolo path rather than the delay path, which is then mixed
down to mono if only the Space output is used. In both cases, the signal passes through the full tremolo
path. (The effects loop is contained within the “Time” sub-circuit, so when Time is disabled, Loop also has
no effect.) This means the Input Gain control also impacts the signal level in bypass mode.
Original Lovetones only used DPDT footswitches, so none of them are true bypass. However, even
with a 3PDT, true bypass is not really possible for this particular circuit due to the stereo operation.
Therefore, unlike our other Lovetone adaptations, for the Xenotron we opted to leave the bypass
switching exactly as in the original. (We still specify 3PDTs due to standard availability, but only two
poles are used in each.) When both modes are active, you have to hit two footswitches to fully bypass
the effect. They’re close enough that they can be pressed at the same time, but it’s a little more
complicated than most effects.
Rotary switch
The original unit has a rotary switch for the LFO shape. This is a 4-position switch that selects between
pairings of LFO modes for Space and Time. Rotary switches are a sort of signature aesthetic for
Lovetone, with each of their pedals having at least one. However, in this circuit, it’s really performing
two separate functions in a logic-table setup (i.e. AA, AB, BA and BB). It’s much more straightforward,
not to mention space-efficient, to control these features with two 2-position toggle switches.
Power handling
As mentioned in the user manual of the original pedal, this circuit is designed for 9V supply with a
maximum voltage of 12V. There is no overvoltage protection, so be very careful to ensure that the
correct power supply is used.
If you accidentally plug in an 18V supply and it stops working, the most likely culprit is the BBD (IC3) and
possibly the clock (IC4). All the other components should be able to handle 18V with no trouble, but the
BBD has a strict maximum of 10V. The BBD supply voltage is dropped by a 330R resistor (R77), which is
enough to keep a 12V supply safely below 10V, but not an 18V supply.

XENOTRON MODULATION MACHINE 5
USAGE
The Xenotron has the following controls. This is only a very surface-level overview and is not a
substitute for reading the full user’s manual for the original unit, which includes extensive information
on each control as well as a block diagram that is crucial for understanding the high-level functionality.
Potentiometers
• Input Gain sets the signal level of the input for the purpose of optimizing the signal-to-noise ratio.
This remains part of the signal path in bypass mode. If you want to set it for unity gain, you’ll either
need a true-bypass looper or a good auditory memory when removing it from the signal chain.
• Action sets the mix level of the delay path. At the center position, the modulation is essentially out
of the mix. To the left, the signal is mixed out-of-phase, and to the right, it’s mixed in-phase.
• Reaction sets the amount of regeneration (feedback) for the delay path, which also passes through
the FX loop (called Loopage on the original). As with the Action control, at the center position there
is no feedback. To the left, odd harmonics are emphasized, with even harmonics to the right.
• Rate sets the speed of the LFO. The rate is shared by both Space and Time modes.
• Depth sets the depth or intensity of the Time mode. Space mode is always fixed at maximum depth.
• Manual sets the delay offset, which changes the modulation character from phasing at low settings,
to flanging at medium setting, and into chorusing and doubling at higher settings. At either extreme,
modulation depth will be reduced since the delay can only go in one direction rather than wavering
above and below a set delay time.
Switches
• Space Shape (toggle switch) selects between sine wave and square wave LFO for the space mode
(tremolo).
• Time Shape (toggle switch) selects between sine wave and square wave LFO for the time mode
(flanger/chorus).
• Mono/Stereo (toggle switch) selects the phase of the “Time Out” jack in bypass mode. If both
outputs are being used, then it should typically be set to Stereo, but some setups may need Mono
depending on the phase of the rest of the signal chain.
• Ring Lift (toggle switch) disconnects the ring (middle) terminal of the Time jack, which is equivalent
to the “C” solution in the user manual under the “Time Out” heading without requiring a specially-
modified cable. Note that this prevents the Time signal from being mixed to mono when only the
Space output is used, so it should only be engaged when both outputs are used and only if you
notice a buzz or weak signal from the Time output.
• Space (footswitch) engages or disengages the tremolo effect.
• Time (footswitch) engages or disengages the time-based modulation effect.
• Loop (footswitch) engages or disengages the effects loop, which is only active when Time is enabled.

XENOTRON MODULATION MACHINE 6
USAGE, CONT.
External jacks
• Loop Send/Return is the effects loop that is engaged with the Loop footswitch. When nothing is
connected, the send is normalized to the return, so the Loop footswitch has no effect. This is where
a lot of the circuit’s magic comes from, so get creative. Try putting a delay pedal in the FX loop as a
good starting point.
• Trig/Gate is a stereo jack with two functions.
○If the plug is inserted all the way (i.e. signal is applied to the jack’s tip connection), then the Gate
function is activated. A positive DC voltage of at least 0.7V will cause the LFO to lock in place.
Brief voltage spikes will cause the LFO to sync to an external signal.
○If the plug is inserted halfway (i.e. signal is applied to the jack’s ring connection) then the Trigger
function is activated. This works the opposite of Gate, with the LFO resetting when a static
positive voltage is periodically grounded, which is how most tap tempo pedals are wired.
○For tempo sync functionality, you’ll want to first manually set the rate as close as possible to the
actual tempo. The trigger and gate only reset the LFO, they don’t impact the rate of sweep. It’s a
great way to close the gap from “almost” to “perfect”, but if the manual setting is too far off the
trigger tempo, the transition will be very abrupt every time it is reset.
• CV In/Pedal allows the modulation to be controlled with either an external control voltage or with
an expression pedal. The Manual control impacts the range of the CV or expression pedal, and
should be set low when using an external source to give the widest possible range.

XENOTRON MODULATION MACHINE 7
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 10k Metal film resistor, 1/4W
R2 1M2 Metal film resistor, 1/4W
R3 4k7 Metal film resistor, 1/4W
R4 330R Metal film resistor, 1/4W
R5 10k Metal film resistor, 1/4W
R6 2M2 Metal film resistor, 1/4W
R7 4k7 Metal film resistor, 1/4W
R8 1k Metal film resistor, 1/4W
R9 330R Metal film resistor, 1/4W
R10 39k Metal film resistor, 1/4W
R11 470k Metal film resistor, 1/4W
R12 100k Metal film resistor, 1/4W
R13 2k2 Metal film resistor, 1/4W
R14 2k2 Metal film resistor, 1/4W
R15 2M2 Metal film resistor, 1/4W
R16 470k Metal film resistor, 1/4W
R17 2M2 Metal film resistor, 1/4W
R18 470k Metal film resistor, 1/4W
R19 68k Metal film resistor, 1/4W
R20 1M2 Metal film resistor, 1/4W
R21 2k2 Metal film resistor, 1/4W
R22 1k Metal film resistor, 1/4W
R23 1k Metal film resistor, 1/4W
R24 330R Metal film resistor, 1/4W
R25 39k Metal film resistor, 1/4W
R26 39k Metal film resistor, 1/4W
R27 1M2 Metal film resistor, 1/4W
R28 2k2 Metal film resistor, 1/4W
R29 1k Metal film resistor, 1/4W
R30 100R Metal film resistor, 1/4W
R31 1k Metal film resistor, 1/4W
R32 470k Metal film resistor, 1/4W
Interactive BOM →

XENOTRON MODULATION MACHINE 8
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R33 39k Metal film resistor, 1/4W
R34 470k Metal film resistor, 1/4W
R35 4k7 Metal film resistor, 1/4W
R36 39k Metal film resistor, 1/4W
R37 330R Metal film resistor, 1/4W
R38 3k9 Metal film resistor, 1/4W
R39 100k Metal film resistor, 1/4W
R40 4k7 Metal film resistor, 1/4W
R41 10k Metal film resistor, 1/4W
R42 39k Metal film resistor, 1/4W
R43 4k7 Metal film resistor, 1/4W
R44 22k Metal film resistor, 1/4W
R45 2M2 Metal film resistor, 1/4W
R46 4k7 Metal film resistor, 1/4W
R47 330R Metal film resistor, 1/4W
R48 4k7 Metal film resistor, 1/4W
R49 10k Metal film resistor, 1/4W
R50 100k Metal film resistor, 1/4W
R51 100k Metal film resistor, 1/4W
R52 39k Metal film resistor, 1/4W
R53 10k Metal film resistor, 1/4W
R54 100k Metal film resistor, 1/4W
R55 1M2 Metal film resistor, 1/4W
R56 10k Metal film resistor, 1/4W
R57 4k7 Metal film resistor, 1/4W
R58 39k Metal film resistor, 1/4W
R59 100R Metal film resistor, 1/4W
R60 10k Metal film resistor, 1/4W
R61 39k Metal film resistor, 1/4W
R62 22k Metal film resistor, 1/4W
R63 39k Metal film resistor, 1/4W
R64 100k Metal film resistor, 1/4W
R65 39k Metal film resistor, 1/4W
R66 1k Metal film resistor, 1/4W
R67 1k Metal film resistor, 1/4W
R68 2k2 Metal film resistor, 1/4W
R69 10k Metal film resistor, 1/4W

XENOTRON MODULATION MACHINE 9
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R70 47R Metal film resistor, 1/4W
R71 47R Metal film resistor, 1/4W
R72 330R Metal film resistor, 1/4W
R73 120k Metal film resistor, 1/4W
R74 68k Metal film resistor, 1/4W
R75 100k Metal film resistor, 1/4W
R76 100k Metal film resistor, 1/4W
R77 330R Metal film resistor, 1/4W
R78 10k Metal film resistor, 1/4W
R79 100k Metal film resistor, 1/4W
R80 4k7 Metal film resistor, 1/4W
R81 120k Metal film resistor, 1/4W
R82 100k Metal film resistor, 1/4W
R83 10k Metal film resistor, 1/4W
R84 100k Metal film resistor, 1/4W
R85 10k Metal film resistor, 1/4W
R86 470k Metal film resistor, 1/4W
R87 100k Metal film resistor, 1/4W
R88 2k2 Metal film resistor, 1/4W
R89 2k2 Metal film resistor, 1/4W
R90 39k Metal film resistor, 1/4W
R91 10k Metal film resistor, 1/4W
R92 100k Metal film resistor, 1/4W
R93 39k Metal film resistor, 1/4W
R94 22k Metal film resistor, 1/4W
R95 47R Metal film resistor, 1/4W
R96 47R Metal film resistor, 1/4W
C1 100n Film capacitor, 7.2 x 2.5mm
C2 10uF Electrolytic capacitor, 5mm
C3 10n Film capacitor, 7.2 x 2.5mm
C4 10uF Tantalum capacitor, 044A Can also use electrolytic, but the original unit uses tantalum here.
C5 100n Film capacitor, 7.2 x 2.5mm
C6 100n Film capacitor, 7.2 x 2.5mm
C7 100n Film capacitor, 7.2 x 2.5mm
C8 100n Film capacitor, 7.2 x 2.5mm
C9 100n Film capacitor, 7.2 x 2.5mm
C10 100n Film capacitor, 7.2 x 2.5mm

XENOTRON MODULATION MACHINE 10
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C11 47n Film capacitor, 7.2 x 2.5mm
C12 10uF Electrolytic capacitor, 5mm
C13 100n Film capacitor, 7.2 x 2.5mm
C14 100n Film capacitor, 7.2 x 2.5mm
C15 10uF Electrolytic capacitor, 5mm
C16 47n Film capacitor, 7.2 x 2.5mm
C17 10uF Electrolytic capacitor, 5mm
C18 100n Film capacitor, 7.2 x 2.5mm
C19 1n Film capacitor, 7.2 x 2.5mm
C20 3n3 Film capacitor, 7.2 x 2.5mm
C21 100n Film capacitor, 7.2 x 2.5mm
C22 10uF Electrolytic capacitor, 5mm
C23 10n Film capacitor, 7.2 x 2.5mm
C24 470n Film capacitor, 7.2 x 3mm
C25 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C26 220uF Electrolytic capacitor, 6.3mm BBD supply filter capacitor.
C27 47uF Electrolytic capacitor, 5mm Power supply filter capacitor.
C28 100n MLCC capacitor, X7R Power supply filter capacitor.
C29 2n2 Film capacitor, 7.2 x 2.5mm
C30 100n Film capacitor, 7.2 x 2.5mm
C31 100pF PP Film capacitor, polypropylene, 1% See build notes for capacitor selection.
C32 100n MLCC capacitor, X7R BBD supply filter capacitor.
C33 100n MLCC capacitor, X7R BBD supply filter capacitor.
C34 10uF Electrolytic capacitor, 5mm Must be low-profile (7mm) or else be folded over adjacent parts.
C35 2n2 Film capacitor, 7.2 x 2.5mm
C36 100n Film capacitor, 7.2 x 2.5mm
C37 100n Film capacitor, 7.2 x 2.5mm
C38 100n Film capacitor, 7.2 x 2.5mm
C39 220uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C40 220uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C41 100n MLCC capacitor, X7R Power supply filter capacitor.
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 1N914 Fast-switching diode, DO-35

XENOTRON MODULATION MACHINE 11
PARTS LIST, CONT.
PART VALUE TYPE NOTES
Q1 BC549C BJT transistor, NPN, TO-92
Q2 BC549C BJT transistor, NPN, TO-92
Q3 J113 JFET, N-channel
Q4 BC549C BJT transistor, NPN, TO-92
Q5 J113 JFET, N-channel
Q6 J113 JFET, N-channel
Q7 BC549C BJT transistor, NPN, TO-92
Q8 BC549C BJT transistor, NPN, TO-92
Q9 BC549C BJT transistor, NPN, TO-92
Q10 BC549C BJT transistor, NPN, TO-92
Q11 BC559C BJT transistor, PNP, TO-92 NOTE: Q11 is the only PNP transistor. See build notes.
Q12 J113 JFET, N-channel
Q13 BC549C BJT transistor, NPN, TO-92
Q14 BC549C BJT transistor, NPN, TO-92
Q15 BC549C BJT transistor, NPN, TO-92
Q16 BC549C BJT transistor, NPN, TO-92
Q17 J113 JFET, N-channel
IC1 TL022 Operational amplifier, dual, DIP-8 Can also use LM358 or other low-current types.
IC1-S DIP8 socket IC socket, DIP-8
IC2 TL022 Operational amplifier, dual, DIP-8 Can also use LM358 or other low-current types.
IC2-S DIP8 socket IC socket, DIP-8
IC3 v3207 BBD, 1024-stage, DIP-8 Original uses Panasonic MN3207.
IC3-S DIP8 socket IC socket, DIP-8
IC4 v3102 Two-phase clock generator, DIP-8 Original uses Panasonic MN3102.
IC4-S DIP8 socket IC socket, DIP-8
BBD BIAS 25k trimmer Trimmer, 10%, 1/4"
REGEN BIAS 25k trimmer Trimmer, 10%, 1/4"
XFM1 LM-NP-1001-B1L Transformer, line matching, 600:600 Bourns LM-NP-1001-B1L. See build notes.
LED1 5mm green LED, 5mm, green diffused See build notes for LED/LDR information.
LED2 5mm green LED, 5mm, green diffused See build notes for LED/LDR information.
LED3 5mm green LED, 5mm, green diffused See build notes for LED/LDR information.
LED4 5mm green trans. LED, 5mm, green transparent Mouser 604-WP7113GT or similar. See build notes.
LDR1 NSL-19M51 LDR, 20-100k light, 20M dark See build notes for LED/LDR information.
LDR2 NSL-19M51 LDR, 20-100k light, 20M dark See build notes for LED/LDR information.
LDR3 NSL-19M51 LDR, 20-100k light, 20M dark See build notes for LED/LDR information.
LDR4 NSL-19M51 LDR, 20-100k light, 20M dark See build notes for LED/LDR information.
10A-13A 40-pin header Header strip, 40-pin male One strip that can be split into four 4-pin male headers.

XENOTRON MODULATION MACHINE 12
PARTS LIST, CONT.
PART VALUE TYPE NOTES
10B 4-pin header Header, 4-pin female
See build notes and assembly instructions for more
information on headers.
11B 4-pin header Header, 4-pin female
12B 4-pin header Header, 4-pin female
13B 4-pin header Header, 4-pin female
INPUT GAIN 100kB 16mm right-angle PCB mount pot
ACTION 100kB 16mm right-angle PCB mount pot
REACTION 100kB 16mm right-angle PCB mount pot
LFO RATE 100kA 16mm right-angle PCB mount pot
DEPTH 100kA 16mm right-angle PCB mount pot
MANUAL 100kB 16mm right-angle PCB mount pot
SPACE SHAPE SPDT Toggle switch, SPDT on-on
TIME SHAPE SPDT Toggle switch, SPDT on-on
MONO/STEREO SPDT Toggle switch, SPDT on-on
RING LIFT SPDT Toggle switch, SPDT on-on
IN 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
SPACE OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
TIME OUT NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S
SEND NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S
RETURN NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S
TRIG/GATE NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S
CV IN/PEDAL NMJ6HCD2 1/4” phone jack, stereo, switched Neutrik NMJ6HCD2 (PCB-mount variant of the HC-S).
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
SPACE 3PDT Stomp switch, 3PDT
TIME 3PDT Stomp switch, 3PDT
LOOP 3PDT Stomp switch, 3PDT
SPACE LED 5mm red LED, 5mm, red diffused
TIME LED 5mm green LED, 5mm, green diffused
LOOP LED 5mm yellow LED, 5mm, yellow diffused
ENCLOSURE 1590XX Enclosure, die-cast aluminum 1790NS equivalent.

XENOTRON MODULATION MACHINE 13
SETTING THE BBD BIAS
Bias adjustments should be made in a dimly lit room, and it’s recommended to cover the pedal with a
towel or T-shirt in such a way that the four LDRs are prevented from picking up ambient light. The top of
the BBD sub-board can be partially exposed for adjustment since the LDR is on the bottom side.
To start with, set the BBD bias trimmer to the 12:00 position, and then down just slightly (the equivalent
of 15 minutes in clock terms, or 11:45). We tested both Panasonic MN3207 and Coolaudio v3207 and
found that they both had the exact same optimal bias point when changing between the two types.
Component tolerances have improved greatly since the unit was first released in 2000, so it’s likely that
the ideal bias range will be much narrower than on original units. You may not need to change the bias at
all from this point.
To verify it’s set properly, first set the controls as follows:
• Input Gain, Action, Manual, Depth, and LFO Rate fully clockwise (all the way up)
• Reaction at center (12:00)
• Space Shape and Time Shape toggles to triangle wave (switch down)
• Stereo/Mono set to Mono (switch down)
• Time mode on, Space mode off, Loop off (or nothing connected to send/return jacks)
• Regen Bias (trimmer) to 2:00
Connect a guitar to the input of the pedal, and connect the Space Out/Mono jack to the amp. Set the
amp volume to zero, power it on, and then turn up the volume until the guitar volume is normal when
strumming. (With “Input Gain” set fully up, the pedal output will be higher than a normal guitar signal.)
Now, listen for distortion, static and clock noise as you adjust the knobs. First turn the “Rate” control
down slowly to zero. Then turn “Manual” to 12:00 and turn “Rate” up slowly until you’re back up at full
rotation. If at any time you hear any clock ticking, or if you hear distortion, static or hum, make small
adjustments to the trimmer until it goes away, and then sweep the controls again to ensure that it’s been
eliminated across the full range.
The goal is a complete range of control with no clock ticking and minimal distortion. The BBDs have a
fixed amount of headroom, so there will eventually be distortion if the input signal is hot enough, but the
“Input Gain” control can compensate for high input levels so the distortion can be dialed out.
Oscilloscope adjustment
If you have an oscilloscope, the bias adjustment procedure is similar to other BBD circuits. The optimal
bias point is where the two halves of the waveform are symmetrical, measured at the “TEST -/+” pads of
the BBD board. It’s recommended to use a test signal with enough amplitude to intentionally overload
the BBD so you can more easily identify the flat-topped symmetry in the scope output as the trimmer is
adjusted.
We expect to update this document with additional scope adjustment procedures including a waveform
image of our calibrated prototype for reference, but this is not ready as of the project’s initial release.

XENOTRON MODULATION MACHINE 14
SETTING THE REGEN TRIMMER
The regen trimmer sets the maximum amount of regeneration or feedback in the “Time” circuit, which is
adjusted by the Reaction control (no feedback at the 12:00 position, odd harmonics emphasized to the
left, and even harmonics emphasized to the right). The feedback path also includes the effects loop.
Feedback is increased with longer delay times, so you’ll want the Manual control turned up somewhat in
order to get the most out of this feature. The circuit is designed to oscillate when the “Reaction” control
is turned down past 9:00 or up past 3:00.
As with the BBD bias, regen calibration should be done in a dimly lit room, and it’s recommended to
cover the pedal with a towel or T-shirt in such a way that the four LDRs are prevented from picking up
ambient light. The Regen Bias trimmer is located along the bottom edge of the main board.
To start with, ensure the Regen Bias trimmer is still set to 2:00 from the BBD bias procedure. This was
the position where our prototype matched an original Lovetone unit, and due to improved component
tolerances since 2000, it’s likely that this setting will be all that’s needed to make yours sound like ours.
However, the user manual provides information on adjusting the trimmer, both due to personal
taste (how much you like oscillation) and due to differences in intended operating voltages, since the
oscillation behavior changes when switching between 9V and 12V power.
So while some original units definitely sound better than others, and much or most of this is due to the
setting of the Regen trimmer, it’s still considered a user-adjustable feature, in contrast with the BBD
bias which the manual warns against adjusting.
To verify it’s set properly, first set the controls as follows:
• Input Gain, Action, Manual, and LFO Rate fully clockwise (all the way up)
• Reaction at 12:00
• Depth fully counter-clockwise (all the way down)
• Space Shape and Time Shape toggles to triangle wave (switch down)
• Stereo/Mono set to Mono (switch down)
• Time mode on, Space mode off, Loop off (or nothing connected to send/return jacks)
Connect a guitar to the input of the pedal, and connect the Space Out/Mono jack to the amp. Set the
amp volume to zero, power it on, and then turn up the volume until the guitar volume is normal when
strumming. (With “Input Gain” set fully up, the pedal output will be higher than a normal guitar signal.)
Now, adjust the “Reaction” control toward 3:00. Once you hit that point, if there is self-oscillation then
turn the Regen trimmer clockwise very slightly until it goes away. Then turn “Reaction” up very slightly,
to about 3:30. If you don’t hear oscillation then turn the trimmer very slightly counterclockwise until
you hear it. Try to find the trimmer position where it starts just barely after 3:00, but not at 3:00 sharp.
Now, check the 9:00 position and ensure that the same thing happens (oscillation starting just after 9:00
on the rotation as it’s turned toward zero). It will sound different, but the oscillation itself should happen
at roughly the same spot on the opposite side of the control.

XENOTRON MODULATION MACHINE 15
BUILD NOTES
Headers and sockets
The BBD sub-board is attached using standard pin headers and sockets that are also used in many other
types of DIY electronics such as Arduino shields. You’ll need four 4-pin sockets and one snap-apart male
header with at least 16 pins that can be broken into four 4-pin headers.
The best ones we’ve found are from Tayda Electronics. They’re cheaper than the ones from Mouser and
also make a much tighter connection with more tension. Here are the links:
• 4-pin female header (4 needed)
• 40-pin snap-apart male header (1 needed)
See pages 19-20 for information and diagrams about how to install this sub-board.
BBD sub-board orientation
The BBD sub-board has a notch in the upper-left corner (looking from the top, not the component side)
which lines up with a diagonal line on the main PCB. Always ensure it is re-inserted correctly any time
you remove it. Permanent damage could result if it’s rotated 180 degrees when power is applied.
Securing the BBD PCB
When the pedal is in playing position, gravity will be pulling against the BBD board, and it could
potentially be knocked loose with enough shock. Once the pedal is fully tested and working, you may
want to attach some non-conductive adhesive foam to the inside of the lid that is thick enough to press
down against the PCB when it’s closed. Make sure the offboard wires are routed around it so that they
aren’t pressed up against the PCB.
Alternately, you could also use some hot glue on the headers, or any other idea you may have. Just
ensure you’ve secured it somehow if you’re planning on using the pedal in a live environment.
LDR selection
While the original LDRs used in the Flange With No Name are unknown, the Advanced Photonix
NSL-19M51 is a likely candidate that meets the specifications for all four positions. It has been tested
extensively in this circuit and has been found to perform identically, and it’s readily available from
Digikey and Mouser.
LED selection
The first three LED/LDR pairs work best with 5mm diffused green LEDs, and these ones from Tayda
Electronics have been tested and work perfectly. You can also use other green diffused LEDs, just make
sure they’re not the high-brightness or low-current type. There are also some diffused types that have a
much higher MCD brightness specification, and these will not work well.
The fourth LED, located on the BBD sub-board, should be a water-clear or semi-transparent high-
brightness type. The Kingbright WP7113GT has been tested and works well.

XENOTRON MODULATION MACHINE 16
BUILD NOTES, CONT.
What about heat shrink?
Homemade optocouplers are very common among DIYers since they can be made for less than 50 cents
compared to true vactrols that can cost around $6 to $8 USD each. This involves using heat shrink to
seal the LED and LDR from outside light, as shown in this Instructable.
However, the original Lovetone unit does not use any sort of light seal on the LED/LDR pairs. When
developing the Quadratron (Doppelganger), it was found when testing against a real Doppelganger
that the clone only sounded exactly like an original when they were unsealed. While this is anecdotal, it
seemed as though there was some crosstalk between the LEDs and LDRs such that as one LED lights up,
it affects the other LDRs slightly as well.
Therefore, to be as accurate to the original unit as possible, it’s recommended to leave the LED/LDR
pairs uncovered as in the original unit, angled toward each other and making physical contact.
Having uncovered LDRs does present a problem for those who like to test the effect outside of the
enclosure before boxing it up, because it will only work properly if the environment is as dark as the
inside of the enclosure would be. This is also an issue when biasing. You can try wrapping it in a towel or
putting it in a closed box while testing.
LDR positioning
For the curious: we intentionally laid out the PCB so that LDR1 and LDR2 are adjacent to each other
and offset slightly, as they are in the original unit’s layout, so LDR1 would pick up a very small amount
of direct light from LED2 but not vice-versa. LDR3 is isolated from the other two by the C8 and C10
box-film capacitors which form a wall of sorts, so it will pick up ambient light but not direct light. LDR4 is
located farther away, so it will only pick up a small amount of ambient light.
This is almost certainly unnecessary, but light is a tricky thing to manage in electronic circuits, and LDRs
are already temperamental enough as it is. You never know what might make a difference.
What about vactrols?
It may be tempting to use a manufactured optocoupler (vactrol) such as the VTL5C3 for the LED/LDR
pairs for convenience and consistency. This will result in a functional effect, but it will not sound the
same since there is no equivalent vactrol with the same specifications as the LED/LDRs used in the
original flanger.
BBD selection
The original Lovetone unit used Panasonic MN3207 BBDs. The Coolaudio v3207 is a direct clone of the
MN3207 with the same specifications.
We tested prototypes with both MN3207 and v3207 against the original unit and they each sounded
identical, so we’re confident in saying that the Coolaudio reissues are a spot-on replacement.
Most of the MN3207s for sale these days are either fake or pulled from recycled electronics, so if you
use one, make sure to test it in another known-working circuit before trying it in this one.

XENOTRON MODULATION MACHINE 17
BUILD NOTES, CONT.
C4 capacitor type
C4 is a 10uF tantalum capacitor in the original unit. Since all of the other 10uF capacitors are
electrolytic, this was clearly an intentional choice on the part of the designer, though we’re not sure of
the purpose. An electrolytic capacitor would work fine here, but if using a tantalum, make absolutely
sure it’s inserted with the correct polarity. Tantalums are much more susceptible to damage from
reversed polarity and may be permanently damaged if installed backwards.
C31 capacitor type
BBD clocks benefit from a high-quality timing capacitor. The original Flange With No Name uses a large
axial polystyrene capacitor for C31. These have exceptional temperature stability and generally low
tolerances. We’ve included space for this type of capacitor on the BBD sub-board.
However, we were unable to find a polystyrene 100pF capacitor from Mouser, so we opted for
polypropylene 1%, which are available in either axial or box-film formats from Vishay. They aren’t cheap,
but they are exceptionally high quality, and it’s what we used in our prototype that was tested against an
original Lovetone unit. These can be found in the parts spreadsheet.
If you would rather use polystyrene, the FSC series from LCR has a suitable 100pF 160V 2.5% capacitor
that is available from Newark and Farnell.
Note that C31 is composed of two overlapping footprints on the PCB, one for an axial capacitor and one
for a 5mm box film type. The outer pads are connected, so just use the inner or outer set of pads and
ignore the other two. No jumper wires are needed in either case.
C34 capacitor orientation
C34 is a 10uF electrolytic capacitor located on the BBD sub-PCB. There’s only about 10mm of clearance
between the BBD board and the main board, so while a low-profile 7mm capacitor will fit just fine, the
standard 11mm height will not. If you only have the 11mm type available, it can easily be folded over
the adjacent resistors—just make sure to bend the legs before soldering and install it at a right angle,
because the legs won’t be long enough to fold the capacitor over after soldering.
Q11 transistor
The Xenotron has 17 transistors in total: five JFETs, 11 NPNs and only one PNP. Be very careful to
ensure that Q11 is a BC559C, not BC549C as all the others are. It is very, very easy to overlook this and
the LFO will not work if the wrong type is used.
Q11 was a BC307B in the original unit, but these are obsolete. The BC559C is the current-production
PNP counterpart to the BC549, so it’s recommended to use this for Q11 instead of trying to hunt down
the exact type and risk fakes or off-spec parts.
Transistor substitution
The original Lovetone unit used the European BC-series transistors. These are still readily available in
through-hole format, so we’ve specified the BC549C for all NPN transistors and the BC559C for the
PNP transistor. If you want to use standard USA types, the 2N5088 is the BC549C equivalent and the

XENOTRON MODULATION MACHINE 18
BUILD NOTES, CONT.
2N5087 is the BC559C equivalent PNP transistor. Just make sure to rotate them 180 degrees from the
silkscreen since the pinout is mirrored. Extra pads have also been included so that you can also use SOT-
23 (SMD) transistors and JFETs.
Transformer selection
The original Lovetone unit used the OEP1200 for the transformer. These are still possible to find, but
they’re expensive. It’s recommended to use the Bourns LM-NP-1001-B1L, which is cheap and readily
available and has the exact same specifications.
Transformer orientation
Both the Bourns transformer and the original OEP1200 are fully symmetrical with no primary and
secondary, so it doesn’t matter which way it’s inserted as long as it lines up with the pads on the PCB.
CV In/Expr. sub-PCB
Take note of the two resistors on the underside of the CV In/Expr. PCB. These should be soldered before
the jack. If you do forget to do this, you can trim the legs before insertion and solder them from the
component side, but it’s tedious.
Please ensure the CV In / Expr. jack is installed the correct way on the sub-PCB since the pin pattern is
symmetrical and it will fit either direction. The open end of the jack should face away from the wire pads.
This may seem basic, but it’s an easy mistake! We do not sell the sub-PCBs separately at this time.
Omitting the CV In/Expr jack
If you don’t want to use the CV In/Expr jack, you can just omit the sub-PCB entirely and leave the wire
pads disconnected on the main board. No jumpers are necessary. The two resistors on the sub-PCB are
only in the circuit when the jack is being used, so they can be left out of the circuit.
Omitting the Trig/Gate jack
If you don’t have any need for the Trig/Gate functionality, the jack can be omitted. Leave the Trig/Gate
pads unconnected. No jumpers are necessary.
IC1/IC2 selection
The original unit used a single quad op-amp for the LFO, but the back was sanded down so the type is
unknown. The LM324 is a likely candidate since it’s a low-current type that is often seen in LFOs.
We opted to split this into two 8-pin types because there is a wider selection of op-amps in this format.
The TL022 is even more efficient than the LM324, so it’s recommended for use in IC1 and IC2, but the
LM358 (the dual version of the LM324) can be used as well.

XENOTRON MODULATION MACHINE 19
BBD SUB-BOARD ASSEMBLY INSTRUCTIONS
The Xenotron uses a “sandwich” configuration for the BBD sub-board for both space efficiency
and signal separation. It’s not particularly difficult, but there’s only one right way to put it together
and several wrong ways that may ruin your build if you’re not careful. Make sure you have a good
understanding of what the end result should look like before you begin installing any components.
The diagrams show an approximate side profile of the PCB as viewed from the left side. Scale and visible
components are not exact.
Step 1
Populate the PCBs according to the silkscreen. The Xenotron is composed of four sub-PCBs, and all four
boards have components mounted to both the top and bottom sides. Components are always mounted
to the side with the silkscreen footprint.
Step 2
Install the header sockets on the top side of the main PCB. It’s recommended to turn the PCB upside
down to hold all of them in place while soldering. Solder one leg of each header, then check them from
the side to make sure they are straight and perpendicular with the PCB before soldering the remaining
legs. If any of them are crooked, reflow the solder and adjust them as needed.
Step 3
With the header sockets installed to the main PCB, insert the male headers, separated into four 4-pin
strips. The long side goes into the socket and the short side faces up.

XENOTRON MODULATION MACHINE 20
BBD SUB-BOARD ASSEMBLY INSTRUCTIONS, CONT.
Step 4
With the male header sockets in place, put the BBD sub-board in position, components facing down.
Ensure the angled notch is in the upper-left and lines up with the small diagonal line on the main
PCB. (The headers and pins should always mount to the side with the rectangular outline on the PCB
silkscreen.)
Once everything is in place, solder the pins to the top PCB. The top PCB can then be removed and set
aside until final assembly.
It’s done in this order so that that the pins are perfectly coupled with the headers. If they were soldered
separately from each other, the slight misalignments between the pins and headers would create stress
that could potentially cause cracked solder joints over time.
From here, you can proceed with the rest of the build as normal. It’s recommended to first attach the
potentiometers and switches to the drilled enclosure and then solder the main PCB in place. This way,
the enclosure acts as a template that ensures the pots and switch are mounted at the correct height, and
it will help compensate for any slight drilling inaccuracies in the enclosure.
Even if you decide to then remove the PCB to test outside the enclosure before final boxing, this method
will ensure there is no long-term stress on the joints of the PCB-mounted components once everything
is reassembled.
Here is a diagram of the completed pedal once it’s installed and wired in the enclosure: