Aion Electronics Isotope User manual

ISOTOPE AMP OVERDRIVE 1
PROJECT NAME
ISOTOPE
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Intersound IVP Tube Voice
The overdrive channel of the Intersound IVP Preamp, adapted for pedal use.
Tube-like overdrive 1.0.0 (2020-06-05)
BUILD DIFFICULTY
Intermediate
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

ISOTOPE AMP OVERDRIVE 2
TABLE OF CONTENTS
1Project Overview 7Enclosure Layout
2Introduction & Usage 8Wiring Diagram
3-4 Parts List 9Licensing
5Schematic 9Document Revisions
6Drill Template
INTRODUCTION
The Isotope Amp Overdrive is an adaptation of the “Tube Voice” channel of the Intersound Instrument
Voicing Preamplifier, a rack preamp from the late 1970s that was favored by Steve Albini and the
Grateful Dead among others.
The IVP’s Tube Sound channel was unique in its method of overdriving the signal. There are no diodes
to be found, but rather, the signal is clipped by overloading a miniature transformer. Add in a two-band
tone control and you’ve got a really flexible circuit that doesn’t look or sound quite like anything else.
The Isotope Amp Overdrive is a greatly reduced version of the IVP, extracting just the Tube Voice
channel which makes up approximately 25% of the whole preamp circuit, which also includes a clean
channel and 4-band parametric equalizer. It’s been adapted to run off of +/-9V instead of +/-15V like the
original. However, all the character of the drive channel is retained and it makes a great standalone drive
pedal if you want something a little different!
One thing to mention: the Treble knob can create oscillations at the very high end of rotation. We tried
several things to mitigate this during development, including better power filtering and tweaking the
values of the treble control, even a new PCB layout, but nothing really fixed it. However, since it only
impacts the last 5-10% of the rotation which is really outside the useful range of the control, we opted
to release it as-is.
USAGE
The Isotope has the following controls:
• Drive controls the amount of gain in the op-amp stage that is fed into the transformer. Overloading
the transformer pushes it into clipping.
• Treble is a half of a Baxandall tone stack affecting the high frequencies.
• Bass is the other half of a Baxandall tone stack affecting the low frequencies.
• Master controls the overall output of the effect.

ISOTOPE AMP OVERDRIVE 3
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 5k6 Metal film resistor, 1/4W
R5 5k6 Metal film resistor, 1/4W
R6 220k Metal film resistor, 1/4W
R7 3k3 Metal film resistor, 1/4W
R8 3k3 Metal film resistor, 1/4W
R9 10k Metal film resistor, 1/4W
R10 4k7 Metal film resistor, 1/4W
R11 10k Metal film resistor, 1/4W
R12 1k1 Metal film resistor, 1/4W
R13 1k1 Metal film resistor, 1/4W
R14 430R Metal film resistor, 1/4W
R15 270k Metal film resistor, 1/4W Original unit uses 430k here, but 270k is the appropriate substitute to
keep the bias the same at +/-9V.
R16 36k Metal film resistor, 1/4W
R17 56k Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor.
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 47n Film capacitor, 7.2 x 2.5mm
C2 10uF Electrolytic capacitor, 5mm
C3 47n Film capacitor, 7.2 x 2.5mm
C4 470pF MLCC capacitor, NP0/C0G
C5 47pF MLCC capacitor, NP0/C0G Original uses 22pF here. 47pf helps prevent oscillation.
C6 10uF Electrolytic capacitor, 5mm
C7 10uF Electrolytic capacitor, 5mm
C8 100uF Electrolytic capacitor, 6.3mm Power filter capacitor.
C9 10uF Electrolytic capacitor, 5mm
C10 100uF Electrolytic capacitor, 6.3mm Charge pump negative supply filter capacitor.
C11 100n MLCC capacitor, X7R Main power filter capacitor.

ISOTOPE AMP OVERDRIVE 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C12 470n MLCC capacitor, X7R Charge pump negative supply filter capacitor.
C13 100n MLCC capacitor, X7R IC1 positive supply filter capacitor.
C14 100n MLCC capacitor, X7R IC1 negative supply filter capacitor.
C15 100n MLCC capacitor, X7R IC2 positive supply filter capacitor.
C16 100n MLCC capacitor, X7R IC2 negative supply filter capacitor.
C17 100uF Electrolytic capacitor, 6.3mm Power filter capacitor.
D1 1N5817 Schottky diode, DO-41
Q1 2N5210 BJT transistor, NPN, TO-92 Can also substitute 2N3904 or 2N5088.
Q2 2N5210 BJT transistor, NPN, TO-92 Can also substitute 2N3904 or 2N5088.
Q3 2N5210 BJT transistor, NPN, TO-92 Can also substitute 2N3904 or 2N5088.
IC1 TL072 Operational amplifier, DIP-8
IC1-S DIP-8 socket IC socket, DIP-8
IC2 RC4558P Operational amplifier, DIP-8
IC2-S DIP-8 socket IC socket, DIP-8
IC3 TC1044SCPA Charge pump, DIP-8
IC3-S DIP-8 socket IC socket, DIP-8
TRANS 42TM018 Transformer, audio, 10KCT/10KCT
TREBLE 50kB 16mm right-angle PCB mount pot
BASS 50kB 16mm right-angle PCB mount pot
DRIVE 100kA 16mm right-angle PCB mount pot Original value is 50kA, but 100k gives more drive range.
MASTER 50kA 16mm right-angle PCB mount pot
LED 5mm LED, 5mm, red diffused
IN 1/4" stereo 1/4" phone jack, closed frame Switchcraft 112BX or equivalent.
OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
BATT Battery snap 9V battery snap Optional. Use the soft plastic type—the hard-shell type will not fit.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

SCHEMATIC
ISOTOPE AMP OVERDRIVE 5
1N5817
+9V
100n
BYP_GND
GND
100uF
50kB
50kB
100kA
50kA
VA
10k
2M 2M
GND
TC1044SCPA
10uF
100uF
PWR_GND
-VA
10uF
5k6
5k6
220k 47n
TL072P
VA
-VA
GND
470pF
3k3
3k3
10k
RC4558P
-VA
VA
47pF
10uF
GND
4k710k
GND
2N5210
1k1 1k1
VA VA
2N5210
430R
36k 270k
VA
-VA -VA
42TM018
GND
10uF
GND
RC4558P
TL072P
56k
GND
47n
470n
100n
GND
100n
GND
100n
GND
100n
GND
100uF
PWR_GND
GND PWR_GND
D1
IN
OUT
C11 C8
BASS
1
2
3
TREBLE
1
2
3
DRIVE
1
2
3
MASTER
1
2
3
R1
R2 R3
1
2
3
4 5
6
7
8
IC3
C9
C10
C2
R4
R5
R6 C3
IC1B
6
5
7
84
C4
R7
R8
R9 2
3
1
IC2A
84
C5
C6
R10R11
Q1
R12 R13
Q2
Q3
R14 R16 R15
TRANSFORMER
1
2
3 4
5
6
C7
6
5
7
IC2B
2
3
1
IC1A
R17
C1
C12
C13
C14
C15
C16
C17
P
S

ISOTOPE AMP OVERDRIVE 6
DRILL TEMPLATE
Cut out this drill template, 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 this template is printed at 100% or “Actual Size”. You can double-check this by measuring
the scale on the printed page.
Top jack layout assumes the use of closed-frame jacks like the Switchcraft 111X. If you’d rather use
open-frame jacks, please refer to the Open-Frame Jack Drill Template for the top side.
LED hole drill size assumes the use of a 5mm LED bezel, available from several parts suppliers. Adjust
size accordingly if using something different, such as a 3mm bezel, a plastic bezel, or just a plain LED.
0 1 2
CM
0 1
INCH
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
125B
MASTER DRIVE
BASS TREBLE
FOOTSWITCHLED
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.65, y: +0.41
ø9/32”
x: 0.65, y: +0.41
ø9/32”

ISOTOPE AMP OVERDRIVE 7
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

ISOTOPE AMP OVERDRIVE 8
WIRING DIAGRAM
125B
IN +VGND GND N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT
Shown with optional 9V battery. If battery is omitted, both jacks can be mono rather than one being stereo.
Leave the far-right lug of the DC jack unconnected.

ISOTOPE AMP OVERDRIVE 9
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 (2020-06-05)
Initial release.