aion IVP Preamp User manual

IVP PREAMP 1
PROJECT NAME
IVP PREAMP
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Intersound™ IVP
A pedal conversion of the Intersound Instrument Voicing Preamplifier, a rack unit from the late 1970s
notably used by Steve Albini (Shellac) and Bob Weir (Grateful Dead).
Preamp & tube overdrive simulator 1.0.0 (2021-07-30)
BUILD DIFFICULTY
Expert
Actual size is 7.15” x 2.30” (main board) and 6.61” x 0.67” (bypass board).
This is a complex circuit and it takes experience and attention to detail in order to build it
successfully. If you’ve never built a guitar pedal before, this shouldn’t be your first. Please read all of
the build documentation to familiarize yourself with the project before you begin. Aion FX cannot
provide direct technical support.
IMPORTANT NOTE

IVP PREAMP 2
TABLE OF CONTENTS
1Project Overview 16-17 Schematic
2Introduction 18-19 Drill Template
3-4 Circuit Design Notes 20 Enclosure Layout
5-6 Usage 21-22 Wiring Diagram
7-12 Parts List 23 Licensing
13-15 Build Notes 23 Document Revisions
INTRODUCTION
The IVP Preamp is based on the Intersound™ Instrument Voicing Preamp (IVP), a rackmounted preamp
that was first released in 1978. The IVP has a six EQ bands (four semi-parametric and two Baxandall)
and two channels, clean and drive.
The drive channel, called “Tube Voice”, is of particular interest and is the main reason for its enduring
reputation. It uses a combination of op-amp gain, a transistor amplifier and a transformer to get its
overdrive tone—no clipping diodes in sight. All of the EQ comes before the overdrive, so it can be used as
a tool to get a wide variety of drive tones and clipping characteristics.
The “Tube Voice” channel doesn’t quite nail the tube tone as it claims, but it’s such a unique sound that
the IVP has built up a reputation in the four decades since its release. Steve Albini is perhaps the most
well-known advocate of the IVP, using it as part of his own live rig as well as in the studio. It was also
used by Bob Weir of the Grateful Dead.
The Aion FX IVP Preamp is a direct clone of the rackmounted unit in pedal format. It runs on the same
voltage as the original, using a DC-DC converter to get +/-15V from a standard 9VDC input. The Clean
and Tube Voice channels are footswitchable, and the other footswitch allows the whole unit to be
bypassed. It does not include the two effects loops (pre-drive and post-drive) by default, although these
can be added with a few trace cuts, described in the build notes.
The Isotope Amp Overdrive is another project based on the IVP, an adaptation of just the Tube Voice
channel and 2-band Baxandall EQ. It’s much simpler to build, but without the parametric EQ and clean
channel, it’s a very different piece of gear than the full IVP.

IVP PREAMP 3
CIRCUIT DESIGN NOTES
Parametric EQ scaling
The original IVP uses 2MC (reverse audio or reverse log) potentiometers for the parametric EQ section.
This value is almost impossible to find today. There are two available options to get around this:
Option 1: Use 1MC potentiometers instead of 2MC with no other changes
This reduces the frequency range of each control, raising the lower frequency by around 30% in each
band, with the upper-end frequency staying the same. The lower frequencies are affected as follows:
• Low: 30 Hz →40 Hz
• Low-Mid: 100 Hz →130 Hz
• High-Mid: 450 Hz →620 Hz
• High: 1.2kHz →1.6kHz
Since the four bands overlap, and are rarely used at the lower extreme of rotation, this has almost no
practical impact on the usability of the EQ. However, we can do even better than this.
Option 2: Use 1MC potentiometers and scale all resistors and capacitors in the EQ section
The gyrators can easily be recalibrated to have the same frequency range by way of something called
scaling. Since the potentiometer (which acts as a resistor) is cut in half, all of the other resistors in the EQ
section should also be reduced by half, and the capacitors should be doubled in value.
The only caveat with scaling is that it results in some non-standard resistor and capacitor values—and
in the case of the capacitors, some values that don’t exist. Since precision is important, we’ve taken the
straightforward route of adding a second capacitor of the same value in parallel with each of them so
that the scaled value is exact.
Option 2 is electronically identical to the way it’s done in the IVP, so it’s the default in this
implementation. If you build it according to the parts list, each band will have the full frequency range of
the original unit. But if you compare it against the original IVP schematics and want to know why there
are more capacitors and different resistors in the EQ section, this is why.
Power supply design
Like most solid-state preamplifiers of the 1970s and 80s, the IVP operated 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 Lab Series L5 Preamp, which uses the same supply voltage, 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.

IVP PREAMP 4
CIRCUIT DESIGN NOTES, CONT.
Because of this, when developing the IVP project 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$9-13 each), but once you account for the fact
that you no longer need a specialized power adapter, the total cost is about the same.
See the build notes on page 13 for more information on the specific DC-DC converters that are
recommended for use in this project.
Channel levels
The original IVP suffers from a very noticeable volume imbalance between the Clean and Tube Voice
channels. If the Tube Voice channel is run at high drive levels (which affects its amount of distortion, not
just its volume), the clean channel doesn’t have enough volume to match it, meaning there’s no way to
switch seamlessly between Clean and Tube Voice without adjusting the master volume.
This is impractical for live use. Because of this, the volume level of the clean channel has been boosted
so the range is closer to the Tube Voice channel and they can be better matched in level when switching
channels. The tone is unchanged.
Input channels
The original IVP has two isolated inputs, each an exact copy of the other. These are labeled as “channels”
on the front panel of the original unit, but there is no switching between the two and they are mixed
together before the EQ after their respective Pregain controls, so they are not channels in the
conventional sense. They serve the same purpose as a an amplifier with two input jacks, though it’s a
little more sophisticated since each input has its own op-amp stage.
Because of this, the pedal conversion removes one of these inputs and simplifies it down to one op-amp
input stage.
Output section
The original IVP has three separate outputs: line level, unbalanced -10dB, and XLR balanced -10dB. For
this project, we’ve converted this to a toggle switch that selects between line level and -10dB. The XLR
output has been eliminated.
If you need XLR, it’s recommended to use an external direct box from the -10dB output. The original
IVP’s XLR output is essentially just a simple direct box, with a single transformer that splits the -10dB
attenuated signal into the inverted copy needed for a balanced connection. An external direct box will
have the exact same result.
Effects loops
The IVP has two effects loops, one that comes after the EQ and one that comes after the clean & drive
channels. While these loops have been omitted from the pedal conversion, they can be added back
without too much trouble. See build notes for more information.

IVP PREAMP 5
USAGE
The IVP has the following controls.
Potentiometers
• Pregain allows the input signal level to be reduced after the input stage. It comes after the Hi/Lo
gain toggle.
• Bass and Treble form a 2-band Baxandall EQ that come before the parametric EQ section. In the
12:00 position, the frequencies are flat. From there, they cut frequencies to the left and boost
frequencies to the right.
• Low Frequency sets the frequency for the lowest parametric band, from 30 Hz to 240 Hz.
• Low-Mid Frequency sets the frequency for the second parametric band, from 100 Hz to 800 Hz.
• Hi-Mid Frequency sets the frequency for the third parametric band, from 460 Hz to 3.6kHz.
• Hi Frequency sets the frequency for the highest parametric band, from 1.2kHz to 9.6kHz.
• Low, Low-Mid, Hi-Mid, and Hi boosts or cuts the frequency selected by the respective frequency
control. In the 12:00 position, the frequency band is flat and essentially out of the circuit. From
there, they cut the frequency to the left and boost the frequency to the right.
• Clean Drive sets the volume level of the clean channel. The tone is unchanged throughout the
rotation and it has no clipping, so its main use is for level-matching with the Tube Drive channel.
• Tube Drive sets both the gain (overdrive) and volume of the Tube Voice channel.
• Master is the master volume of the unit.
Switches
• Input reduces or boosts the gain of the input stage to allow it to be used with a variety of signals.
○High gain mode boosts the signal level with a gain of 4.3 (+12.7dB), suitable for input levels as
low as 50mV RMS. This is the mode that will typically be used for guitar or bass.
○Low gain mode reduces the signal level with an attenuation factor of -33dB. This mode is
suitable for high-output instruments with levels as high as 8V RMS.
• Output selects between two types of output. This comes after the master volume in the circuit.
○Line Out is suitable for going directly to a power amp or crossover.
○-10dB is used if it will be followed by other effects or will be sent to a guitar amp’s input.
○Note that this switch is just a simple attenuator, equivalent to turning the master volume down
slightly, and the master volume setting has a much larger impact on the output signal level.
• Channel (footswitch) changes between Clean and Tube Voice channels.
• Bypass (footswitch) bypasses the effect entirely.

IVP PREAMP 6
USAGE, CONT.
Peak indicator LED
The IVP has a peak indicator LED that senses the signal level and lights up if it gets close to the range
where unwanted clipping will occur. It’s important to understand how this LED works, how to read its
behavior, and how to use it to adjust your levels for the best sound.
First of all, peaking doesn’t necessarily mean clipping. If the levels are set properly, it will occasionally
blink in normal use. The goal is to adjust it so that it comes on sometimes, but not too much. If it never
comes on even with heavy strumming, the internal gain is too low. Conversely, if it’s on even with very
low-level signals, the internal gain is too high.
The IVP has four different areas where the gain can be adjusted:
• Pregain: the signal level coming out of the first op-amp stage (full-range)
• EQ: six frequency bands that can have a cumulative impact on the overall signal level
• Clean / Drive: the gain of the two individual channels, with the drive channel being intentionally
clipped after the gain boost
• Master: the master volume at the tail end of the circuit
The peak detector is located between the EQ and clean/drive sections. If it’s on constantly, it indicates
that some of the earlier stages may have clipped already and that the subsequent stages may clip as well
(prior to any intentional clipping from the drive channel).
With all this in mind, here is the setup procedure.
1. Set the input toggle switch based on the type of signal source. (Normally you’ll use the “high” input
mode. The “low” input mode is only needed if the signal level is so high that the pregain control is
hard to adjust.)
2. Set the bass, treble, and four EQ knobs to the 12:00 position (flat).
3. While strumming chords heavily, adjust the pregain control. Turn it up until the peak LED starts to
blink occasionally at the highest signal levels. If it illuminates for longer than a flicker, back off the
pregain control slightly.
4. Adjust the channel gain (clean or tube) to the desired level, then adjust the EQ until you have the
tone you want. Depending on the EQ adjustment, this may increase the overall gain and cause the
peak indicator LED to illuminate more frequently. If so, turn down the Pregain control again until it’s
back to normal.
5. Adjust the master volume to the desired output level.
If the pregain and EQ have been adjusted, the clean and drive channels and master volume can be at
any gain or volume setting without issue. All of the potential for unwanted clipping comes before those
stages, so the signal levels afterward are unimportant.
Note that if using the pre-voice effects loop, the peak detector comes before the loop, not after, so it
does not detect the level of the returning signal.

IVP PREAMP 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 2M Metal film resistor, 1/4W
R3 2M Metal film resistor, 1/4W
R4 51R Metal film resistor, 1/4W
R5 51R Metal film resistor, 1/4W
R6 43k Metal film resistor, 1/4W
R7 2M Metal film resistor, 1/4W
R8 10k Metal film resistor, 1/4W
R9 20k Metal film resistor, 1/4W
R10 43k Metal film resistor, 1/4W
R11 5k6 Metal film resistor, 1/4W
R12 5k6 Metal film resistor, 1/4W
R13 220k Metal film resistor, 1/4W
R14 3k3 Metal film resistor, 1/4W
R15 3k3 Metal film resistor, 1/4W
R16 20k Metal film resistor, 1/4W
R17 820R Metal film resistor, 1/4W
R18 13k7 Metal film resistor, 1/4W Can also use 14k, or two 27k resistors in parallel.
R19 820R Metal film resistor, 1/4W
R20 13k7 Metal film resistor, 1/4W Can also use 14k, or two 27k resistors in parallel.
R21 820R Metal film resistor, 1/4W
R22 13k7 Metal film resistor, 1/4W Can also use 14k, or two 27k resistors in parallel.
R23 820R Metal film resistor, 1/4W
R24 13k7 Metal film resistor, 1/4W Can also use 14k, or two 27k resistors in parallel.
R25 20k Metal film resistor, 1/4W
R26 13k Metal film resistor, 1/4W
R27 13k Metal film resistor, 1/4W
R28 10R Metal film resistor, 1/4W
R29 10R Metal film resistor, 1/4W
R30 51R Metal film resistor, 1/4W

IVP PREAMP 8
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R31 100k Metal film resistor, 1/4W
R32 JUMPER Metal film resistor, 1/4W Used for effect loop modification. See build notes.
R33 100k Metal film resistor, 1/4W
R34 20k Metal film resistor, 1/4W
R35 10k Metal film resistor, 1/4W
R36 4k7 Metal film resistor, 1/4W
R37 10k Metal film resistor, 1/4W
R38 1k1 Metal film resistor, 1/4W
R39 1k1 Metal film resistor, 1/4W
R40 430R Metal film resistor, 1/4W
R41 36k Metal film resistor, 1/4W
R42 430k Metal film resistor, 1/4W
R43 47k Metal film resistor, 1/4W
R44 4k7 Metal film resistor, 1/4W Original value is 13k. See build notes.
R45 18k Metal film resistor, 1/4W Original value is 36k. See build notes.
R46 10k Metal film resistor, 1/4W
R47 10k Metal film resistor, 1/4W
R48 20k Metal film resistor, 1/4W
R49 13k Metal film resistor, 1/4W
R50 13k Metal film resistor, 1/4W
R51 10R Metal film resistor, 1/4W
R52 10R Metal film resistor, 1/4W
R53 100k Metal film resistor, 1/4W
R54 20k Metal film resistor, 1/4W
R55 4k7 Metal film resistor, 1/4W
R56 20k Metal film resistor, 1/4W
R57 13k Metal film resistor, 1/4W
R58 13k Metal film resistor, 1/4W
R59 10R Metal film resistor, 1/4W
R60 10R Metal film resistor, 1/4W
R61 51R Metal film resistor, 1/4W
R62 100k Metal film resistor, 1/4W
R63 1k1 Metal film resistor, 1/4W
R64 510R Metal film resistor, 1/4W
R65 47k Metal film resistor, 1/4W

IVP PREAMP 9
PARTS LIST, CONT.
PART VALUE TYPE NOTES
R66 47k Metal film resistor, 1/4W
R67 4M7 Metal film resistor, 1/4W
R68 4k7 Metal film resistor, 1/4W
R69 160k Metal film resistor, 1/4W
R70 220k Metal film resistor, 1/4W
LEDC 4k7 Metal film resistor, 1/4W
LEDR 10k Metal film resistor, 1/4W
LEDT 10k Metal film resistor, 1/4W
C1 47uF Electrolytic capacitor, 5mm
C2 47pF MLCC capacitor, NP0/C0G
C3 100uF Electrolytic capacitor, 6.3mm
C4 47uF Electrolytic capacitor, 5mm
C5 47uF Electrolytic capacitor, 5mm
C6 100n MLCC capacitor, X7R
C7 100n MLCC capacitor, X7R
C8 10uF Electrolytic capacitor, 5mm
C9 47pF MLCC capacitor, NP0/C0G
C10 10uF Electrolytic capacitor, 5mm
C11 47n Film capacitor, 7.2 x 2.5mm
C12 470pF MLCC capacitor, NP0/C0G
C13 100n MLCC capacitor, X7R
C14 100n MLCC capacitor, X7R
C15 470n Film capacitor, 7.2 x 3mm
C16 68n Film capacitor, 7.2 x 2.5mm
C17 68n Film capacitor, 7.2 x 2.5mm
C18 120n Film capacitor, 7.2 x 2.5mm
C19 120n Film capacitor, 7.2 x 2.5mm
C20 6n8 Film capacitor, 7.2 x 2.5mm
C21 6n8 Film capacitor, 7.2 x 2.5mm
C22 100n MLCC capacitor, X7R
C23 100n MLCC capacitor, X7R
C24 68n Film capacitor, 7.2 x 2.5mm
C25 1n2 Film capacitor, 7.2 x 2.5mm
C26 1n2 Film capacitor, 7.2 x 2.5mm
C27 6n8 Film capacitor, 7.2 x 2.5mm

IVP PREAMP 10
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C28 6n8 Film capacitor, 7.2 x 2.5mm
C29 820pF MLCC capacitor, NP0/C0G
C30 820pF MLCC capacitor, NP0/C0G
C31 100n MLCC capacitor, X7R
C32 100n MLCC capacitor, X7R
C33 22pF MLCC capacitor, NP0/C0G Original uses 20pF here. 22pF is the closest common value.
C34 10uF Electrolytic capacitor, 5mm
C35 10uF Electrolytic capacitor, 5mm
C36 100n MLCC capacitor, X7R
C37 100n MLCC capacitor, X7R
C38 10uF Electrolytic capacitor, 5mm
C39 22pF MLCC capacitor, NP0/C0G Original uses 20pF here. 22pF is the closest common value.
C40 10uF Electrolytic capacitor, 5mm
C41 22pF MLCC capacitor, NP0/C0G Original uses 20pF here. 22pF is the closest common value.
C42 100n MLCC capacitor, X7R
C43 100n MLCC capacitor, X7R
C44 47pF MLCC capacitor, NP0/C0G
C45 10uF Electrolytic capacitor, 5mm
C46 10uF Electrolytic capacitor, 5mm
C47 100n MLCC capacitor, X7R
C48 100n MLCC capacitor, X7R
C49 100uF Electrolytic capacitor, 6.3mm
C50 10n Film capacitor, 7.2 x 2.5mm
C51 100uF Electrolytic capacitor, 6.3mm
C52 100uF Electrolytic capacitor, 6.3mm
C53 100uF Electrolytic capacitor, 6.3mm
C54 47uF Electrolytic capacitor, 5mm
C55 10uF Electrolytic capacitor, 5mm
C56 10uF Electrolytic capacitor, 5mm
Z1 1N4743A Zener diode, 13V, DO-41
D1 1N914 Fast-switching diode, DO-35
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

IVP PREAMP 11
PARTS LIST, CONT.
PART VALUE TYPE NOTES
D6 1N914 Fast-switching diode, DO-35
D7 1N914 Fast-switching diode, DO-35
D8 1N914 Fast-switching diode, DO-35
D9 1N914 Fast-switching diode, DO-35
D10 1N914 Fast-switching diode, DO-35
Q1 2N3904 BJT transistor, NPN, TO-92 Substitute. Original uses 2N4401.
Q2 2N3906 BJT transistor, PNP, TO-92 Substitute. Original uses 2N4403.
Q3 2N5088 BJT transistor, NPN, TO-92 Substitute. Original uses 2N5210.
Q4 2N5088 BJT transistor, NPN, TO-92 Substitute. Original uses 2N5210.
Q5 2N5088 BJT transistor, NPN, TO-92 Substitute. Original uses 2N5210.
Q6 2N3904 BJT transistor, NPN, TO-92 Substitute. Original uses 2N4401.
Q7 2N3906 BJT transistor, PNP, TO-92 Substitute. Original uses 2N4403.
Q8 2N3904 BJT transistor, NPN, TO-92 Substitute. Original uses 2N4401.
Q9 2N3906 BJT transistor, PNP, TO-92 Substitute. Original uses 2N4403.
IC1 LF356N Operational amplifier, single, DIP-8
IC1-S DIP8 socket IC socket, DIP-8
IC2 TL072 Operational amplifier, dual, DIP-8
IC2-S DIP8 socket IC socket, DIP-8
IC3 TL072 Operational amplifier, dual, DIP-8
IC3-S DIP8 socket IC socket, DIP-8
IC4 TL072 Operational amplifier, dual, DIP-8
IC4-S DIP8 socket IC socket, DIP-8
IC5 RC4558P Operational amplifier, dual, DIP-8
IC5-S DIP8 socket IC socket, DIP-8
IC6 RC4558P Operational amplifier, dual, DIP-8
IC6-S DIP8 socket IC socket, DIP-8
IC7 RC4558P Operational amplifier, dual, DIP-8
IC7-S DIP8 socket IC socket, DIP-8
IC8 RC4558P Operational amplifier, dual, DIP-8
IC8-S DIP8 socket IC socket, DIP-8
DC1 TEC 3-0923 DC-DC converter, +9V to +/-15V See build notes for alternatives.
XFM1 42TM018 Transformer, audio, 10KCT/10KCT
L1 10uH Inductor, 10uH Bourns 78F100J-RC
L2 10uH Inductor, 10uH Bourns 78F100J-RC
L3 10uH Inductor, 10uH Bourns 78F100J-RC

IVP PREAMP 12
PARTS LIST, CONT.
PART VALUE TYPE NOTES
PREGAIN 50kB 16mm right-angle PCB mount pot
BASS 50kB 16mm right-angle PCB mount pot
TREBLE 50kB 16mm right-angle PCB mount pot
HI 25kB 16mm right-angle PCB mount pot
Original uses 50kB, but all resistors (including potentiometers)
have been scaled to 50% and capacitors doubled to allow 1MC
pots to be used with the same range of frequency. See circuit
design notes for more details.
HI-MID 25kB 16mm right-angle PCB mount pot
LOW-MID 25kB 16mm right-angle PCB mount pot
LOW 25kB 16mm right-angle PCB mount pot
HI FREQ 1MC 16mm right-angle PCB mount pot
Original uses 2MC, but 1MC is the closest available. The
resistors and capacitors have been scaled for the same
frequency range. See circuit design notes for more details.
HI-MID FREQ 1MC 16mm right-angle PCB mount pot
LO-MID FREQ 1MC 16mm right-angle PCB mount pot
LOW FREQ 1MC 16mm right-angle PCB mount pot
CLEAN DRIVE 50kA 16mm right-angle PCB mount pot
TUBE DRIVE 50kA 16mm right-angle PCB mount pot
MASTER 50kA 16mm right-angle PCB mount pot
INPUT SPDT Toggle switch, SPDT on-on
OUTPUT SPDT Toggle switch, SPDT on-on
CLEAN LED 5mm green LED, 5mm, green diffused
TUBE LED 5mm LED, 5mm, red diffused
BYPASS 5mm LED, 5mm, red diffused
OVERLOAD 5mm LED, 5mm, red diffused
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.
PRE-V. SEND NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S. Part of optional effects loop mod.
PRE-V. RET. NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S. Part of optional effects loop mod.
POST-V. SEND NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S. Part of optional effects loop mod.
POST-V. RET. NMJ6HC-S 1/4” phone jack, stereo, switched Neutrik NMJ6HC-S. Part of optional effects loop mod.
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
BYPASS 3PDT Stomp switch, 3PDT
CHANNEL 3PDT Stomp switch, 3PDT
ENCLOSURE 1590DD Enclosure, die-cast aluminum

IVP PREAMP 13
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 other models 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 Digi-Key, 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 less than half the price
of the others (USD$5.87 as of the time of this writing) with the exact same specs. So if you need more
than one, it quickly becomes much more cost-effective than the other options.
Bypass PCB component orientation
Due to the height of the DC converter, 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.

IVP PREAMP 14
BUILD NOTES, CONT.
Using the external effects loops
The original IVP had two effects loops. The first, called “Pre Voice”, comes after the EQ and before the
clean/drive channels. The second, called “Post Voice”, comes after the clean/drive channels and before
the master volume and output section.
The default build configuration of the IVP does not use these effects loops since they aren’t terribly
practical in a pedal conversion. However, they can be added with a few simple trace cuts, some offboard
wiring, and four drill holes.
The wiring diagram for the effects loops is located on page 21. Aside from the extra wires and jacks and
two 51R resistors, each loop requires a trace cut. Here are descriptions of each of the modifications.
Pre-voice loop
The first effects loop is enabled by cutting the trace shown to the right, from
R32 to C35, on the top side of the PCB. After making the cut, do a continuity
check with your multimeter to make sure the left pad of R32 has no connection
with the right pad of C35.
From there, solder one wire from R32’s left pad to the Send jack as shown in
the wiring diagram, and another wire from the right-side pad of R33 to the
Return jack. (This pad is connected to the right-side pad of C35, but it’s easier
to solder the wire to a resistor than the underside of a capacitor.)
R32 (jumper), C35 (10uF) and R33 (100k) should still be installed as normal. The wires need to share the
pads with the components. The easiest method is to elevate the resistor above the PCB slightly before
soldering and then solder the wire underneath the lifted leg.
Post-voice loop
The second effects loop is enabled by cutting the trace shown to the right, from
the left lug of Master to the left lug of R53, also on the top side of the PCB. As
before, do a continuity test with the multimeter to verify no connection.
Solder a wire from R53’s left pad to the Send jack as shown in the wiring
diagram, and a second wire from the left-most lug of the Master potentiometer
to the Return jack. R53 (100k) should still be installed as normal.
Both of these loops have an additional 51R resistor that is shown in the wiring
diagram between the Send and Return jacks. The way it’s wired, this resistor is in series with the only
Send jack of each loop, and is out of the circuit entirely when nothing is plugged into the Return jack.
The Send jacks can be used to send a copy of the signal offboard, but only the Return of each loop is
wired as a transfer jack. This means that unless the Return jack is used, the signal will not be interrupted.

IVP PREAMP 15
BUILD NOTES, CONT.
Clean channel volume
The original IVP has one severe but easily remedied design issue: the clean channel’s maximum volume
is much, much lower than the drive channel’s maximum.
While this can be compensated on a per-channel basis by adjusting the master volume to get the same
levels, channel switching is almost unusable in a live setting unless the drive channel is set very low and
the clean channel is set at maximum.
Fortunately, we only need to adjust two resistors that set the gain and mix ratio of the clean channel in
order to boost its level relative to the drive channel and allow it to match the drive channel volume.
R44 sets the gain ratio of the potentiometer. By reducing it from 13k (stock) to 4k7, the range of the
clean level knob is almost tripled.
R45 sets the mix ratio of the clean channel relative to the drive channel. It’s already mixed about 25%
higher than the drive channel, but it’s not enough. By reducing the resistor from 36k (stock) to 18k, the
mix is more like 2:1.
With these two changes, the clean channel can keep up just fine with the drive channel, with no change
in tone. This project uses the modified values by default.
R40 value
Both revisions of the IVP factory schematic show R40 as 43R. However, the parts list in the service
manual lists it as 430R, and it’s been verified in multiple actual units as being 430R. It appears to have
been an error in the first version of the schematic that was inadvertently copied over to the second
version, but it does not reflect production units.

SCHEMATIC (MAIN CIRCUIT)
IVP PREAMP 16
OUT
LINE
-10dB
IN
GND
50kB
50kB
50kB
50kA
50kA
10k
2M
47uF
2M
GND
LF356N
1N914
1N914
51R51R
43k
47pF
47uF
-VA
GND
47uF
VA
GND
100uF
2M
GND
10k
GND
10uF
GND
20k
TL072P
43k
GND
47pF
10uF
5k6
5k6
220k 47n
TL072P
VA
-VA
GND
470pF
3k3
3k3
20k
25kB
25kB
25kB
25kB
470n
820R
68n
TL072PTL072P
1MC
13k7
GND
120n
820R
6n8
1MC
13k7
GND
68n
820R
1n2
1MC
13k7
GND
6n8
820R
1MC
13k7
GND
820pF
TL072PTL072P
VA VA
-VA -VA
RC4558P
RC4558P
20k
22pF
1N9141N914 13k
VA
-VA
13k
10R10R
2N3904
VA
2N3906
-VA
51R
10uF
100k
GND
JUMPER
100k
20k
10uF
GND GND
-VA
VA
10uF
10k
4k7
RC4558P
RC4558P
-VA
VA
22pF
10uF
50kA
22pF
GND
GND
4k710k
GND
2N5088
1k1 1k1
VA VA
2N5088
430R
36k 430k
VA
-VA -VA
42TM018
GND
47k
10k
18k
10k
RC4558P
RC4558P
GND
-VA
VA
20k
47pF
1N9141N914 13k13k
2N3904
VA VA
10R10R
2N3906
-VA -VA
10uF
100k
GND
10uF
GND
20k
20k
4k7
GND
GND
1N9141N914 13k13k
10R10R
VA
-VA
2N3904
2N3906
-VA
VA
51R
100uF
100k
GND
1k1510R
GND
47k
47k
4M7
JRC4558D
JRC4558D
VA
-VA
1N914
GND
1N914
10n
GND GND
5MM
4k7
160k
220k
VA
-VA
100n
100n
GND
GND
68n 120n 6n8
6n8 820pF1n2
PREGAIN
1
2
3
BASS
1
2
3
TREBLE
1
2
3
TUBE DRIVE
1
2
3
MASTER
1
2
3
TR TS
R1
R2
C1
R3
IC1
5
1
2
3
6
8
74
D1
D2
R4R5
R6
C2
C4
C5 C3
R7
INPUT
-33dB +12dB
2
31
R8
C8
R9
2
3
1
IC2A
R10
C9
C10
R11
R12
R13 C11
6
5
7
IC2B
84
C12
R14
R15
R16
LO
1
2
3
LO-MID
1
2
3
HI-MID
1
2
3
HI
1
2
3
C15
R17
C17
2
3
1
IC3A
6
5
7
IC3B
LOFREQ
1
2
3R18
C18
R19
C20
LO-MID-FREQ
1
2
3R20
C24
R21
C25
HI-MID-FREQ
1
2
3R22
C27
R23
HIFREQ
1
2
3R24
C29
2
3
1
IC4A
6
5
7
IC4B
84 84
2
3
1
IC5A
6
5
7
IC5B
84
R25
C33
D3D4 R26R27
R28R29
Q1
Q2
R30
C34
R31
R32
R33
R34
C35
C38
R35
R44
2
3
1
IC6A
84
6
5
7
IC6B
C39
C40
CLEAN DRIVE
1
2
3
C41
R36R37
Q3
R38
R39
Q4
Q5
R40
R41 R42
XFM1
1
2
3 4
5
6R43
R46
R45
R47
2
3
1
IC7A
84
6
5
7
IC7B
R48
C44
D5D6 R49R50
Q6
R51R52
Q7
C45
R53
C46
R54
R56
R55
D7D8 R57R58
R59R60
Q8
Q9
R61
C49
R62
R63R64
R65
R66
R67
2
3
1
IC8A
84
6
5
7
IC8B
D9
D10
2
3
1OUTPUT
C50
OVERLOAD
R68
R69
R70
CSCR
C6
C7
C16 C19 C28
C21 C30C26
P
S

IVP PREAMP 17
SCHEMATIC (POWER AND SWITCHING)
10k
5MM
GND
-VB
LEDR
LED
A2
A3
A1
BYPASS A
B2
B3 B1
BYPASS B
C2
C3
C1
BYPASS C
PCB IN
OUT
JACK
IN
JACK
PCB OUT
+V
+15V
-15V
L1-L3: Bourns 78F100J-RC
GND
1N4743A
GND GND
100uF
GND GND
GND
10uH
10uH
10uF
10uF
10uH
47uF
-VB
VB
Z1
DC1
+VIN
2
-VIN
1
+VOUT 6
COM 7
-VOUT 8
C53
L2
L3
C55
C56
L1
C54
DC/DC CONVERTER
100n
100n
100n
100n
100n
100n
100n
100n
100n
100n
VA
-VA
GND
100n
100n
C13
C14
C22
C23
C31
C32
C36
C37
C42
C43
C47
C48
100uF
100uF
C51
C52
GND
GND
GND
4k7
10k
VB
GREEN
RED
TUBE
SEND
CLEAN
SEND
TUBE
RETURN
CLEAN
RETURN
A2
A3
A1
CHANNEL A
B2
B3
B1
CHANNEL B
C2
C3 C1
CHANNEL C
LEDC LEDT
TUBE LED
CLEAN LED
Channel switching
Power supply
Power filtering
Bypass switching

IVP PREAMP 18
DRILL TEMPLATE
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 LED drill holes are sized for plain LEDs with no bezel. If you don’t have a 5mm bit, use 7/32”.
The DC jack is offset by 0.5” to account for the additional screw anchor in the center of the 1590DD
enclosure’s long side.
The drill template includes holes for the optional effects loop jacks. The process for adding these is
described on page 14. If you’re not using these, the four holes should be omitted.

IVP PREAMP 19
DRILL TEMPLATE
0 1 2
CM
0 1
INCH
x: -2.25, y: +1.58
ø9/32”
x: -1.35, y: +1.58
ø9/32”
x: +0.45, y: +1.58
ø9/32”
x: -0.45, y: +1.58
ø9/32”
x: +1.35, y: +1.58
ø9/32”
x: +2.25, y: +1.58
ø9/32”
x: -3.15
y: +0.43
ø1/4”
x: +3.15
y: 0
ø5mm
x: 2.93, y: -1.58
ø15/32”
x: -2.93, y: -1.58
ø15/32”
CENTER (0,0)
ø7/16”
0.396”
(10.1mm)
-1.25”
(-31.8mm)
1.25”
(31.8mm)
-0.5”
(-12.7mm)
HORIZONTAL
CENTER
0.396”
(10.1mm)
-2.125”
(-54.0mm)
2.125”
(54.0mm)
-3.00”
(-76.2mm)
3.00”
(76.2mm)
ø7/16”
ø3/8” ø7/16” ø7/16” ø3/8”
ø1/2”
0.396”
(10.1mm)
OUTPUT
TREBLE
x: -3.15, y: +1.58
ø9/32”
PREGAIN LEVEL
LOW
LEVEL
LOW-MID
x: +2.15
y: -1.43
ø5mm
CLEAN
x: +2.15
y: -1.73
ø5mm
DRIVE
x: -2.15
y: -1.58
ø5mm
PEAK
LEVEL
HIGH-MID
LEVEL
HIGH
DRIVE
CLEAN
DRIVE
TUBE
x: -2.25, y: +0.43
ø9/32”
x: -1.35, y: +0.43
ø9/32”
x: +0.45, y: +0.43
ø9/32”
x: -0.45, y: +0.43
ø9/32”
x: +1.35, y: +0.43
ø9/32”
x: +2.25, y: +0.43
ø9/32”
BASS FREQUENCY
LOW
FREQUENCY
LOW-MID
FREQUENCY
HIGH-MID
FREQUENCY
HIGH
x: +3.15, y: +1.58
ø9/32”
MASTER
CHANNEL
BYPASS
INPUT
x: +3.15
y: +0.43
ø1/4”
OUTPUT
(OPTIONAL) (OPTIONAL)
RETURN
POST-VOICE
SEND
POST-VOICE
(OPTIONAL) (OPTIONAL)
RETURN
PRE-VOICE
SEND
PRE-VOICE
DC INPUT

IVP PREAMP 20
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring. If using effects loops, see alternate wiring diagram on page 21
and information on page 14.
1590DD