aion Lab Series User manual

L5 PREAMP 1
PROJECT NAME
L5 PREAMP
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Lab Series®L5 Preamp
A pedal adaptation of the two-channel preamp of the Lab Series® L5 amplifier from the late 1970s,
often considered to be the best solid-state amp ever designed.
Preamp, overdrive & compressor 1.0.0 (2023-07-04)
BUILD DIFFICULTY
Advanced
Actual size is 5.48” x 2.61” (main board) and 4.90” x 0.71” (bypass board).

L5 PREAMP 2
TABLE OF CONTENTS
1Project Overview 14-15 Schematic
2Introduction 16-17 Drill Template
3Usage & Circuit Design Notes 18 Enclosure Layout
4Circuit Design Notes 19 Wiring Diagram
5-10 Parts List 20 Licensing
11-13 Build Notes 20 Document Revisions
INTRODUCTION
The L5 Preamp is a pedal conversion of the preamp of the Lab Series® L5 guitar amplifier, a Moog-
designed solid-state amplifier from the late 1970s that is widely considered the best and most tube-like
solid-state amplifier ever made. It has two channels which are both merged into a shared distortion/
master volume circuit as well as a compressor/limiter.
The original amps had the preamp integrated with the power amp. By splitting out the preamp, we can
use this either as a normal pedal in a chain (e.g. tuner →overdrive →L5 Preamp →modulation / delay
→amp input) or as a true preamp by plugging its output straight into a power amp (either a dedicated
power amp or just the “return” jack of an amp with an effects loop). The main difference will be the
volume setting. It’s capable of enormous signal levels, far more than any stompbox—so if you’re using it
like a pedal, it’s normal to keep the master volume down really low.
The updated L5 Preamp is a full redesign of our original project from 2016. The biggest difference is that
it’s much easier to build, with greatly simplified wiring and a cleaner layout. It also now runs on standard
9V DC power instead of AC like our earlier one.
There are also a few circuit tweaks. The first is a new feature: making the Multifilter section switchable
so that it can be applied to either channel. There’s still only one of them, but now people who prefer
channel 1 can also experience the unique sounds of the multifilter.
The second tweak was to reconfigure the input op-amp stages as non-inverting, which cuts down on
noise and is typically viewed as better design practice. We’ve done simulations and A/B tests to ensure
the tone is unchanged.
The third change is to remove the hi/lo switches for each channel, which corresponded to the hi/lo
inputs in the original amp, and hardwired it to “Lo” mode (i.e. the one intended for low-level signals,
providing more gain boost at the input). The only function of the “Hi” input was to attenuate the input,
but the attenuated input sounds dull and lifeless in nearly any normal use case. You’ll generally get
better results just turning down the channel volume if the “Lo” input is too hot with your instrument.
Lab Series®is a registered trademark of Gibson Brands. Use of the Lab Series name is not endorsed by Gibson
and is used for comparative purposes only.

L5 PREAMP 3
USAGE
The L5 Preamp has the following controls:
Channel 1
• Bright (toggle switch) adds a treble-bleed capacitor to the volume control, which preserves some of
the treble at lower volume levels to keep it from getting dull.
• Treble, Mid and Bass form a standard Fender-style 3-band passive EQ.
• Volume controls the amount of gain in the first stage, before the EQ and drive section.
Channel 2
• Bright (toggle switch) adds a treble-bleed capacitor to the volume control, which preserves some of
the treble at lower volume levels to keep it from getting dull.
• Volume controls the amount of gain in the first stage, before the EQ and drive section.
• Treble and Bass form a standard 2-band Baxandall control. Each band is flat at the 12:00 position,
and can either cut (CCW) or boost (CW).
• Mid boosts (CCW) or cuts (CW) the midrange frequency selected by the Frequency control.
• Frequency selects the frequency that will be boosted or cut by the Mid control, from 100 Hz at full
CCW to 6.4kHz at full CW.
Both channels
• Multifilter blends a six-band fixed EQ boost, adding harmonics to the instrument signal.
• Multifilter Channel (toggle) moves the multifilter between channel 1 or channel 2.
• Master sets the output volume after the drive section of the preamp.
• Limit sets the threshold of the compressor at the end of the circuit.
• Comp (toggle) engages or disengages the compressor.

L5 PREAMP 4
CIRCUIT DESIGN NOTES
Power supply design
Like most solid-state preamplifiers of the era, the L5 ran on a bipolar +/-15V supply. This voltage can’t be
supplied by an external adapter, and the current draw of the circuit is too high to use a charge pump.
When developing the original Lab Series L5 Preamp, we adapted a supply scheme from Alesis rack units
in the early 1990s that involved a 9VAC adapter and an AC voltage tripler. This was then rectified to
bipolar +/-19V DC and regulated down to 15V on each rail.
This solution used cheap and readily-available parts, and it has worked very well for several years since
the L5 Preamp was first developed. But the power adapter requirement has always been the major flaw.
A 9VAC adapter will destroy most other pedals if it’s plugged in, and if you own one, there’s an infinitely
higher chance that it’ll be mistaken for a 9VDC adapter and plugged into the wrong pedal at some point.
Because of this, when developing the IVP Preamp project in 2021, we set out to find a reliable way to
supply +/-15V from a standard DC adapter. Fortunately, there are a few more options available today
than there were in 2015 when the L5 Preamp was originally developed, and a high-quality DC-DC
converter module will give us exactly what we need.
They’re not cheap (USD$9-15 each), but once you account for the fact that you no longer need a
specialized power adapter, the total cost is about the same. We have begun using these DC converters
in all of our preamp projects going forward, including this new version of the original L5 project that
started it all.
See the build notes on page 11 for more information on the specific DC-DC converters that are
recommended for use in this project.
Multifilter
The multifilter is a patented Moog invention that uses a set of six fixed-frequency resonant filters to add
a unique harmonic sheen to an instrument signal, sometimes described by Lab Series owners as making
their electric guitar sound more like an acoustic.
On the original amps, the multifilter was hard-wired to take its input signal from channel 2 and had no
function when channel 1 was used. However, in developing this updated version of the L5 project, we
experimented with taking the input from channel 1 instead, and the results were stellar.
There’s a bit of a switch pop when moving the multifilter from one channel to the other, so it’s not
something you’ll want to adjust in a live environment. Also beware that depending on the EQ settings,
there may be feedback on the upper end of the multifilter since it’s operating in a way it wasn’t originally
designed to. Just turn down the multifilter level slightly and it will go away.

L5 PREAMP 5
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 220k Metal film resistor, 1/4W
R3 47k Metal film resistor, 1/4W
R4 2k2 Metal film resistor, 1/4W
R5 1k Metal film resistor, 1/4W
R6 22k Metal film resistor, 1/4W
R7 5k1 Metal film resistor, 1/4W Taper resistor for Mid pot. See build notes.
R8 220k Metal film resistor, 1/4W
R9 47k Metal film resistor, 1/4W 18k in the original amp, but 47k provides better channel matching.
R10 10k Metal film resistor, 1/4W
R11 2k7 Metal film resistor, 1/4W Taper resistor for Volume 1 pot. See build notes.
R12 1k Metal film resistor, 1/4W Taper resistor for Volume 1 pot. See build notes.
R13 6k8 Metal film resistor, 1/4W
R14 10k Metal film resistor, 1/4W
R15 1k5 Metal film resistor, 1/4W
R16 27k Metal film resistor, 1/4W
R17 27k Metal film resistor, 1/4W
R18 18k Metal film resistor, 1/4W
R19 18k Metal film resistor, 1/4W
R20 18k Metal film resistor, 1/4W
R21 18k Metal film resistor, 1/4W
R22 18k Metal film resistor, 1/4W
R23 1k5 Metal film resistor, 1/4W
R24 1k5 Metal film resistor, 1/4W
R25 2k2 Metal film resistor, 1/4W
R26 22k Metal film resistor, 1/4W
R27 2k2 Metal film resistor, 1/4W
R28 100k Metal film resistor, 1/4W
R29 2k2 Metal film resistor, 1/4W
R30 24k Metal film resistor, 1/4W
R31 39k Metal film resistor, 1/4W
R32 270k Metal film resistor, 1/4W
Interactive BOM →

L5 PREAMP 6
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R33 390R Metal film resistor, 1/4W
R34 22k Metal film resistor, 1/4W
R35 300k Metal film resistor, 1/4W
R36 430R Metal film resistor, 1/4W
R37 22k Metal film resistor, 1/4W
R38 240k Metal film resistor, 1/4W
R39 390R Metal film resistor, 1/4W
R40 22k Metal film resistor, 1/4W
R41 300k Metal film resistor, 1/4W
R42 560R Metal film resistor, 1/4W
R43 22k Metal film resistor, 1/4W
R44 220k Metal film resistor, 1/4W
R45 390R Metal film resistor, 1/4W
R46 22k Metal film resistor, 1/4W
R47 150k Metal film resistor, 1/4W
R48 300R Metal film resistor, 1/4W
R49 22k Metal film resistor, 1/4W
R50 18k Metal film resistor, 1/4W
R51 10k Metal film resistor, 1/4W
R52 15k Metal film resistor, 1/4W
R53 1k Metal film resistor, 1/4W
R54 6k8 Metal film resistor, 1/4W
R55 33k Metal film resistor, 1/4W
R56 220R Metal film resistor, 1/4W
R57 10k Metal film resistor, 1/4W
R58 470k Metal film resistor, 1/4W
R59 2k Metal film resistor, 1/4W
R60 47k Metal film resistor, 1/4W
R61 3k3 Metal film resistor, 1/4W
R62 330R Metal film resistor, 1/4W
R63 100k Metal film resistor, 1/4W
R64 6k8 Metal film resistor, 1/4W
R65 15k Metal film resistor, 1/4W
R66 220R Metal film resistor, 1/4W
R67 220R Metal film resistor, 1/4W
R68 820R Metal film resistor, 1/4W
R69 22k Metal film resistor, 1/4W

L5 PREAMP 7
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R70 3k3 Metal film resistor, 1/4W
R71 33k Metal film resistor, 1/4W
R72 10k Metal film resistor, 1/4W
R73 10k Metal film resistor, 1/4W
R74 47k Metal film resistor, 1/4W
R75 47k Metal film resistor, 1/4W
R76 100k Metal film resistor, 1/4W
R77 100k Metal film resistor, 1/4W
R78 10k Metal film resistor, 1/4W
R79 22k Metal film resistor, 1/4W
R80 10M Metal film resistor, 1/4W
R81 2k7 Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor. Can be as low as 1M.
LEDC 10k Metal film resistor, 1/4W Channel 1 LED current-limiting resistor.
LEDD 10k Metal film resistor, 1/4W Channel 2 LED current-limiting resistor.
LEDR 10k Metal film resistor, 1/4W Bypass LED current-limiting resistor.
C1 150n Film capacitor, 7.2 x 2.5mm
C2 22pF MLCC capacitor, NP0/C0G
C3 10uF Electrolytic capacitor, 5mm
C4 10n Film capacitor, 7.2 x 2.5mm
C5 1n2 Film capacitor, 7.2 x 2.5mm
C6 220n Film capacitor, 7.2 x 2.5mm
C7 22pF MLCC capacitor, NP0/C0G
C8 47n Film capacitor, 7.2 x 2.5mm
C9 4n7 Film capacitor, 7.2 x 2.5mm
C10 4n7 Film capacitor, 7.2 x 2.5mm
C11 68n Film capacitor, 7.2 x 2.5mm
C12 4.7uF Electrolytic capacitor, 4mm
C13 68n Film capacitor, 7.2 x 2.5mm
C14 68n Film capacitor, 7.2 x 2.5mm
C15 2n2 Film capacitor, 7.2 x 2.5mm
C16 15n Film capacitor, 7.2 x 2.5mm
C17 15n Film capacitor, 7.2 x 2.5mm
C18 10n Film capacitor, 7.2 x 2.5mm
C19 10n Film capacitor, 7.2 x 2.5mm
C20 8n2 Film capacitor, 7.2 x 2.5mm
C21 8n2 Film capacitor, 7.2 x 2.5mm

L5 PREAMP 8
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C22 4n7 Film capacitor, 7.2 x 2.5mm
C23 4n7 Film capacitor, 7.2 x 2.5mm
C24 4n7 Film capacitor, 7.2 x 2.5mm
C25 4n7 Film capacitor, 7.2 x 2.5mm
C26 4n7 Film capacitor, 7.2 x 2.5mm
C27 4n7 Film capacitor, 7.2 x 2.5mm
C28 2.2uF Film capacitor, 7.2 x 5mm Original amp uses 2.7uF tantalum, but 2.2uF film will work the same.
C29 10n Film capacitor, 7.2 x 2.5mm
C30 220pF MLCC capacitor, NP0/C0G
C31 330n Film capacitor, 7.2 x 2.5mm
C32 68n Film capacitor, 7.2 x 2.5mm
C33 2.2uF Film capacitor, 7.2 x 5mm
C34 100pF MLCC capacitor, NP0/C0G
C35 10uF Electrolytic capacitor, 5mm
C36 100n MLCC capacitor, X7R
C37 100n MLCC capacitor, X7R
C38 100n MLCC capacitor, X7R
C39 100n MLCC capacitor, X7R
C40 100n MLCC capacitor, X7R
C41 100n MLCC capacitor, X7R
C42 22uF Electrolytic capacitor, 5mm
C43 22uF Electrolytic capacitor, 5mm
C44 22uF Electrolytic capacitor, 5mm
C45 22uF Electrolytic capacitor, 5mm
C46 22uF Electrolytic capacitor, 5mm
C47 22uF Electrolytic capacitor, 5mm
C48 22uF Electrolytic capacitor, 5mm
C49 22uF Electrolytic capacitor, 5mm
C50 100n MLCC capacitor, X7R
C51 100uF Electrolytic capacitor, 6.3mm
C52 47uF Electrolytic capacitor, 5mm
D1 1N5817 Schottky diode, DO-41
D2 1N4004 Rectifier diode, DO-41
D3 1N4004 Rectifier diode, DO-41
D4 1N914 Fast-switching diode, DO-35
D5 1N914 Fast-switching diode, DO-35
Z1 1N4742A Zener diode, 12V, DO-41

L5 PREAMP 9
PARTS LIST, CONT.
PART VALUE TYPE NOTES
Q1 2N3904 BJT transistor, NPN, TO-92
Q2 2N3904 BJT transistor, NPN, TO-92
Q3 2N5457 JFET, N-channel, TO-92 Original uses PN4303, but 2N5457 will perform the same.
Q4 2N3906 BJT transistor, PNP, TO-92
Q5 MPSA13 Darlington transistor, NPN, TO-92
IC1 LF356N Operational amplifier, DIP8
IC1-S DIP-8 socket IC socket, DIP-8
IC2 RC4558P Operational amplifier, dual, DIP8
IC2-S DIP-8 socket IC socket, DIP-8
IC3 RC4558P Operational amplifier, dual, DIP8
IC3-S DIP-8 socket IC socket, DIP-8
IC4 RC4558P Operational amplifier, dual, DIP8
IC4-S DIP-8 socket IC socket, DIP-8
IC5 RC4558P Operational amplifier, dual, DIP8
IC5-S DIP-8 socket IC socket, DIP-8
IC6-S DIP-8 socket IC socket, DIP-8
IC7 RC4558P Operational amplifier, dual, DIP8
IC7-S DIP-8 socket IC socket, DIP-8
IC8 RC4558P Operational amplifier, dual, DIP8
IC8-S DIP-8 socket IC socket, DIP-8
IC9 RC4558P Operational amplifier, dual, DIP8
IC9-S DIP-8 socket IC socket, DIP-8
IC10 LM13700N Transconductance amplifier, dual, DIP16 Can also use NE5517N.
IC10-S DIP-16 socket IC socket, DIP-16
IC11 RC4558P Operational amplifier, dual, DIP8
IC11-S DIP-8 socket IC socket, DIP-8
L1 10uH Inductor, 10uH
L2 10uH Inductor, 10uH
L3 10uH Inductor, 10uH
DC1 TEC 3-0923 DC-DC converter, +9V to +/-15V See page 11 for more DC converter options.
COMP. TRIM 20k trimmer Trimmer, 10%, 1/4" Bourns 3362P
DIST. TRIM 20k trimmer Trimmer, 10%, 1/4" Bourns 3362P
BASS 1 25kB 16mm right-angle PCB mount pot
MID 1 5kA 16mm right-angle PCB mount pot Original uses 2.5kA. See build notes.
TREBLE 1 25kB 16mm right-angle PCB mount pot
VOLUME 1 10kB 16mm right-angle PCB mount pot Original uses 2.5kA. See build notes.
BASS 2 25kB 16mm right-angle PCB mount pot

L5 PREAMP 10
PARTS LIST, CONT.
PART VALUE TYPE NOTES
MID 2 25kB 16mm right-angle PCB mount pot
FREQUENCY 100kC dual 16mm dual pot, right angle
TREBLE 2 25kB 16mm right-angle PCB mount pot
VOLUME 2 25kA 16mm right-angle PCB mount pot
MULTIFILTER 25kA 16mm right-angle PCB mount pot
MASTER 25kA 16mm right-angle PCB mount pot
LIMIT 50kC 16mm right-angle PCB mount pot
BRIGHT 1 SPDT Toggle switch, SPDT on-on
BRIGHT 2 SPDT Toggle switch, SPDT on-on
MF CHANNEL SPDT Toggle switch, SPDT on-on
COMP SPDT Toggle switch, SPDT on-on
BYP. LED 5mm red LED, 5mm, red diffused
CH. 1 LED 5mm green LED, 5mm, green diffused
CH. 2 LED 5mm red LED, 5mm, red diffused
LIMIT LED 3mm red LED, 3mm, red diffused
DC JACK 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
IN 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
BYPASS 3PDT Stomp switch, 3PDT
CHANNEL 3PDT Stomp switch, 3PDT
ENCLOSURE 1590XX Enclosure, die-cast aluminum

L5 PREAMP 11
BUILD NOTES
DC converter selection
There are several brands and models available, all with the same pinout and similar specifications. Here
are the DC converters we’ve found that will work in this circuit.
BRAND PART # MOUSER # SUPPLY NOTES
Traco TEC 3-0923 495-TEC3-0923 4.5-13.2V Preferred option. More sources on Octopart.
CUI PQMC3-D12-D15-S 490-PQMC3-D12-D15-S 9-18V
XP Power IZ1215S 209-IZ1215S 9-18V
Recom RS3-1215D 919-RS3-1215D 9-18V
Mornsun WRA1215S-3WR2 N/A 9-18V NAC Semi: https://aionfx.com/link/mornsun/
The Traco TEC 3-0923 is preferred for this circuit because its supply voltage range (4.5V to 13.2V) is
perfectly suited for any type of pedal power supply. The TEC 2-0923 cannot be used since the current
handling is not high enough for the full two-channel preamp.
The other brands all have a minimum supply voltage of 9V. Most nominally 9VDC adapters put out
around 9.6V, which is more than enough—but one very notable exception is the Voodoo Labs Pedal
Power series (and likely other similar pedalboard supplies) which regulate to exactly 9.00V.
These DC converter modules are usually specced very conservatively, so it’s very unlikely that there
would be any issues even if the supply voltage was slightly lower than 9V. However, operating on the
extreme lower end of a spec is not ideal from an engineering standpoint, so if we’re going to point you to
a specific module, it’s going to be the one that works reliably in all use cases.
If you are using a standard wall-wart supply that puts out more than 9V, then all this is immaterial and
any of the five units listed above will work the same. All significant specifications are the same aside
from this input voltage range. We haven’t tried all of them directly, but their datasheets indicate they
will perform identically and they have the same pinout and physical dimensions.
This is fortunate, because most suppliers don’t stock more than 20 or 30 of each type at a time. So while
we recommend the Traco TEC 3-0923 as the best overall, it will likely not always be in stock, especially
as we release more preamp projects with converters and more people are using them.
If you’re having a hard time finding any that will work, try searching Octopart for the part number
shown in the Part # column. Most of these brands are also carried by DigiKey, Newark, and several other
suppliers, and this engine will search all of the major distributors at once for easier sourcing.
The Mornsun unit is not available from Mouser, but it’s included here because it’s cheaper than the
others (USD$8.22 as of the time of this writing) with the exact same specs. If you need more than one, it
quickly becomes much more cost-effective than the other options.

L5 PREAMP 12
BUILD NOTES, CONT.
Calibration
The L5 Preamp has two different calibration trimmers, located on the far-left side of the PCB. To set
these, all you will need is a multimeter and a signal generator (which can be a computer or smartphone).
Note that all voltages are taken in AC, not DC, since we are dealing with audio signal levels. The voltages
are also all RMS rather than p-p, so confirm that your multimeter measures RMS if you’re not sure.
Before you start, turn both trimmers all the way down.
Distortion trimmer
The distortion trimmer should be set first. This sets the level at which the overdrive kicks in. The
procedure calls for a 1kHz 30mV sine wave to be inserted onto pin 13 of IC10, and for the trimmer to be
adjusted until you measure 4.4V on pin 12 of IC10.
For convenience, there is a pair of pads marked “TEST” right underneath the “Frequency”
potentiometer’s pads where you can insert your signal. The “+” pad connects to pin 13 of IC10 and the
other is connected to ground. It’s recommended to solder short pins to these pads (about 3/4” in length)
to act as ‘posts’ for alligator clips to attach to. (The clipped leads from a 1N4004 diode work well for this
since they are more rigid than normal component leads.)
If you don’t have a signal generator, look for a smartphone or Mac/PC app that allows selection of wave
type, frequency and gain level. These come and go, so we can’t recommend anything specific, but there
are several free ones available at any given time and they all do the same basic thing.
From here, hook up a 3.5mm male-to-male headphone cable and turned up the phone or computer
volume to maximum, then set the frequency to 1kHz and the wave type to sine. Using a multimeter set
to AC millivolt mode, adjust the volume in the app until you read 30mV. (Don’t rely on the app to tell you
the output signal level; they have no way of knowing the actual real-world level.)
Now, use alligator clips to connect the sleeve and the tip of the headphone cable to the two wires
coming from the test pad. Since it’s AC, the polarity does not matter. This will insert the signal to pin 13
of IC10 so you can adjust the trimmer as specified earlier, targeting 4.4V on pin 12.
Once you know the correct factory setting, feel free to adjust the trimmer up or down and see if you
prefer it in any other position (but consider first marking the trimmer with a Sharpie so you can get
back to the calibrated setting). Since this is a pedal adaptation, you may find it worthwhile to adjust the
distortion so it comes on earlier than it did in the original amps.
Compressor/limiter trimmer
With the 30mV sine wave signal still inserted into pin 13 of IC10, turn the master volume up all the way
and turn the compressor on (switch in the “up” position). Then turn the compressor knob up to about
2:00 (2/3 of the way up) and touch your probe to the “PCB OUT” pad on the right side of the footswitch
board. Turn the trimmer until you measure 1.17VAC.
This will get you in the range of the original amps. If you’re using the L5 primarily as a pedal, you may
want to set this lower so it’s more sensitive to lower-level signals.

L5 PREAMP 13
BUILD NOTES, CONT.
Channel 1 midrange and volume potentiometer values
The Lab Series amplifier used 2.5kA potentiometers for both Midrange and Volume of channel 1. This
is a non-standard value today and not available from any standard parts suppliers. Tayda Electronics
carries 2kA, which is certainly close enough and will work fine in this circuit. But in the new version of
the L5, we included parallel and tapering resistors on the PCB so standard pot values could be used.
For the midrange pot, we recommend using 5kA, with a 5k1 resistor in parallel (R7). Since it’s wired as a
variable resistor, this drops the resistance value to 2.5k and only steepens the curve slightly.
The volume pot is wired as a true potentiometer with all three terminals used, so it’s a little more
complicated. For this, it’s recommended to use a 10kB pot with a 2k7 resistor (R11) between pins 2 and
3 and a 1k resistor (R12) between pins 1 and 2. This will give a good approximation of a 2.5k pot, and the
resulting taper will be very close to logarithmic.
LM13700 vs. CA3080
Our original L5 Preamp project used CA3080s as in the original amp. These have been discontinued for
a long time, and while they have been reissued and are not terribly hard to find, they are expensive.
The LM13700 is essentially a dual version of the CA3080/CA3094 and is still readily available. Since the
L5 circuit uses two CA3080s, it seemed like a good opportunity to replace them with a single LM13700.
The only change that this required was to add a second 100k resistor (R77) to cut the compressor LED’s
voltage in half, since the LM13700’s IABC pin sits at twice the voltage of the CA3080’s pin. This extra
resistor prevents the LED from staying on all the time, which was the only side-effect of substituting the
LM13700 in place of the CA3080.
Bypass PCB component orientation
Due to the height of the DC converter and electrolytic capacitors, the components on the switching PCB
are mounted on the bottom, the same side as the footswitch. This is in contrast with most other Aion FX
projects where the switch is mounted on the bottom of the switching sub-board and the components
face up. Components are always mounted to the side with the silkscreen footprint.

L5 PREAMP 14
SCHEMATIC (INPUT, CH. 1, CH. 2, MULTIFILTER, SWITCHING)
Input Channel switching Bypass switching
MultifilterChannel 1 & 2
IN
CHANNEL
SWITCH
TO
2k2
47k
1k
LF356
10n
GND
-VA
VA
GND
10k
150n
2M2
GND
220k
GND
10uF
22pF
R4
R3
R5
IC1
5
1
2
3
6
8
74
C4
R1
C1
RPD
R2
C3
C2
MULTIFILTER
INPUT MULTIFILTER
OUTPUT
VA
-VA
A
RC4558
RC4558
270k
390R
22k
15n 15n
GND
300k
10n 10n
430R
22k
GND
RC4558
RC4558
RC4558
RC4558
VA
-VA
240k
8n2 8n2
390R
GND
22k
300k
4n7 4n7
560R
GND
22k
VA
-VA
220k
4n7 4n7
390R
GND
22k
150k
4n7 4n7
300R
GND
22k
B
84
2
3
1
IC6A
6
5
7
IC6B
R32
R33
R34
C16 C17
R35
C18 C19
R36
R37
6
5
7
IC7B
2
3
1
IC7A
6
5
7
IC8B
2
3
1
IC8A
8484
R38
C20 C21
R39
R40
R41
C22 C23
R42
R43
R44
C24 C25
R45
R46
R47
C26 C27
R48
R49
MULTIFILTER
MULTIFILTER
CH.1
CH.2
FROM
OUTPUT
FROM
INPUT
DISTORTION
TO
& LIMITER
5kA 25kB
10kB
25kB
GND
47n
6k8
1n2
22k
220n
GND
5k1
GND
220k
GND
2k71k
GND
47k
VA
-VA
10k
GND
RC4558
4n7
68n
25kB
RC4558
RC4558
RC4558
18k
18k
18k
18k
1k5
1k5
100kC
100kC
GND
27k
18k
27k
GND
GND
25kB
25kA
25kB
RC4558
GND
4n7
10k
1k5
GND
2k22k2
24k
2n2
68n
22k 2k2
68n
100k
GND
39k
RC4558
VA
-VA
-VA
VA
4.7uF
A
B
25kA
18k
GND
22pF
RC4558
RC4558
VA
-VA
GND
GND
C
MID 1
1
2
3
TREBLE 1
1
2
3
VOLUME 1
1
2
3
BASS 1
1
2
3
C8
R13
BRIGHT 1
2
3
1
C5
R6
C6
R7
R8
R11R12
R9
R10
6
5
7
IC2B
84
C10
C11
MID 2
1
2
32
3
1
IC5A
6
5
7
IC5B
2
3
1
IC3A
R21
R20
R22
R19
R23
R24
FREQUENCY A
1
2
3
1
2
3
FREQUENCY B
R16
R18
R17
1
2
3
TREBLE 2
VOLUME 2
1
2
3
BASS 2
1
2
3
6
5
7
IC4B
C9
R14
R15 R25R29
R30
C15
C13
R26 R27
C14
R28
84
84
R31
2
3
1
IC4A
2
3 1
BRIGHT 2
C12
MULTIFILTER
1
2
3
R50
2
3
1
MF CHANNEL
C7
6
5
7
IC3B
2
3
1
IC2A
84
CHANNEL
CH.1
CH.2
CHANNEL A
CHANNEL B
CHANNEL C
CH1 LED CH2 LED 10k
5mm red
GND
GND
5mm green
10k
+9V
C2
C3 C1
B
B3
B1
2
A
A3
A1
2
LEDD
LEDC
BYPASS A
BYPASS C BYPASS B
BYPASS LED
PCB
INPUTINPUT
JACK
FROM
PCB
OUT
FROM
TO
IN
OUTPUT
TO
JACK
10k
5mm red
GND
+9V
LEDR
A2
A3
A1
B2
B3 B1
C2
C3
C1

L5 PREAMP 15
SCHEMATIC (DISTORTION, COMPRESSOR, POWER)
Distortion & compressor
Power supply
100uF
+9V
GND
1N5817
100n
1N4742A
VA
22uF
TEC 3-0923
10uH
10uH
47uF
GNDGNDGNDGNDGND
22uF
10uH
-VA
100n
100n 100n
100n 22uF
22uF
22uF
22uF
22uF
22uF
100n
100n
C51
D1
C50
Z1
C48
DC1
+VIN
2
-VIN
1
+VOUT 6
COM 7
-VOUT 8
L2
L1
C52
C49
L3
C36
C37 C39
C38 C42
C43
C44
C45
C46
C47
C40
C41
DC/DC CONVERTER
OUT
+-
DIST. TRIM
COMP. TRIM
TEST
CHANNEL 1/2 &
FROM
MULTIFILTER
25kA
50kC
10k
GND
15k
10n
6k8
33k
GND
1k
GND
470k
220R
10k
20k
220pF
GND
2N3904
2N3904
3k3 2k47k
330R
330n
100k
68n
2N5457
6k8
15k
10M
GND
820R
100pF
220R 220R
GND GND
2k7
1N4004 1N4004
22k
100k
MPSA13
20k
GND
22k
GND
GND
3k3
RC4558
RC4558
10k
10k
33k
3mm red
2N3906
10k
GND
47k
1N914 1N914
GND
47k
RC4558
LM13700LM13700
VA
-VA
GND
-VA
-VA
-VA
-VA
VA
VA
VA
VA
-VA
2.2uF
2.2uF
GND
10uF
-VA
GND
VA
VA
GND
GND
100k
-VA
GND
GND
RC4558
LM13700
LM13700
VA
-VA
GND
GND
C
MASTER
1
2
3
LIMIT
1
2
3
R51
R52
C29
R54
R55
R53
R58
R56
R57
1
2
3
C30
Q1
Q2
R61 R59R60
R62
C31
R63
C32
Q3
R64
R65
R80
R68
C34
R67 R66
R81
D2 D3
R79
R76
Q5
1
2
3
R69
R70
2
3
1
IC11A
6
5
7
IC11B
R72
R73
R71
LIMIT_LED
Q4
R78
R75
D4 D5
R74
84
2
3
1
IC9A
IC10A
3
4
5
1
2
IC10B
14
13
12
16
15
116
C33
2
3 1
COMP
C28
C35
R77
84
6
5
7
IC9B
IC10_BUF1
V+
7
8
IC10_BUF2
V+
10
9

L5 PREAMP 16
DRILL TEMPLATE INSTRUCTIONS
Cut out the drill template on the following page, 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 the template is printed at 100% or “Actual Size”. You can double-check this by measuring the
scale on the printed page with a ruler or calipers.
The LEDs are sized for plain LEDs with no bezel, mounted directly to the PCB. If you don’t have a 5mm
bit for the bypass and channel LEDs, use 7/32”. If you don’t have a 3mm bit for the limit LED, use 1/8”.
Important: Due to the high number of PCB-mounted parts, it’s crucial that the drilling be accurate. Since
the PCB uses slotted holes for the toggles, there’s not a lot of room for error.
If the toggles don’t align to the PCB, you can always drill one step larger (9/32”) to allow a little more
room correct any errors. The toggle switch washer and nut will still fully cover the hole.

DRILL TEMPLATE
L5 PREAMP 17
0 1 2
CM
0 1
INCH
ø3/8” ø1/2”
0.385”
0.9” 0.9”
ø3/8”
OUT DC IN
x: -2.33, y: +1.58
ø9/32”
x: -2.33, y: +0.43
ø9/32”
x: -1.50, y: +1.58
ø9/32”
x: -1.50, y: +0.43
ø9/32”
x: -0.41, y: +1.58
ø9/32”
x: -0.41, y: +0.43
ø9/32”
x: +0.41, y: +1.58
ø9/32”
x: +0.41, y: +0.43
ø9/32”
x: +1.24, y: +1.58
ø9/32”
x: +1.24, y: +0.43
ø9/32”
x: +2.33, y: +1.58
ø9/32”
x: +2.33, y: +0.43
ø9/32”
x: +2.05, y: -1.90
ø15/32”
x: -2.05, y: -1.90
ø15/32”
x: -1.28, y: -1.75
ø5mm
x: -1.28, y: -2.05
ø5mm
x: +1.28
y: -1.90
ø5mm
CENTER (0,0)
y: -0.57
x: +2.33
ø1/4”
x: +2.33, y: -0.92
ø3mm
x: +0.41, y: -0.57
ø1/4”
x: -0.41, y: -0.57
ø1/4”
x: -2.33, y: -0.57
ø1/4”
LIMIT
MASTERFREQUENCYMIDRANGE 2VOLUME 2MIDRANGE 1VOLUME 1
BASS 2TREBLE 2MULTIFILTERBASS 1TREBLE 1
CHANNEL BYPASS
BRIGHT 2CHANNEL
MULTIFILTER
COMP.BRIGHT 1

ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
L5 PREAMP 18
1590XX
Note: 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 via, 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 upper set
of pins forward slightly so they make
contact with the inside of the pads.

WIRING DIAGRAM
L5 PREAMP 19
OUT IN-V GND
PCB
IN
GND PCB
OUT
-V +V JACK GND JACK
OUTIN
+V A3
1590XX
+V A3
A2 A1
A2 A1

L5 PREAMP 20
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 (2023-07-04)
Initial release.