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
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