aion Particle User manual

PARTICLE VINTAGE FUZZ 1
PROJECT NAME
PARTICLE
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Interfax Harmonic Percolator
An obscure and very unique germanium fuzz/drive circuit from the 1970s, famously used and revered by
Steve Albini.
Fuzz / Overdrive 1.0.2 (2022-09-20)
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.87” (bypass board).
BUILD DIFFICULTY
Easy

PARTICLE VINTAGE FUZZ 2
TABLE OF CONTENTS
1Project Overview 6Drill Template
2Introduction & Usage 7Enclosure Layout
3Parts List 8Wiring Diagram
4Build Notes 9Licensing
5Schematic 9Document Revisions
INTRODUCTION
The Particle Germanium Fuzz is an adaptation of the Interfax HP-1 Harmonic Percolator, an extremely
rare and highly sought-after fuzz/overdrive from the mid-1970s. Not much is known about the history of
the unit other than that they were made in Milwaukee, Wisconsin by Ed Geise, owner of an electronics
repair shop called Interfax Electronics.
The Harmonic Percolator is a two-transistor fuzz, but it bears no resemblance to any other of its
contemporary pedals such as the Fuzz Face or any of the Tone Bender variants. It uses a PNP germanium
transistor paired with an NPN silicon, allowing it to run in a standard negative-ground configuration.
The transistors and some of the components were gooped or obscured in the original. To add the
mystery, there were several circuit changes made throughout the run, so even if you manage to find one,
there’s no guarantee that it’s one of the “good” ones.
The Particle is an exact replica of the known schematics of the Harmonic Percolator, but with one
addition. The Harmonic Percolator uses clipping diodes (unlike most germanium fuzzes) and so as with
other Aion FX projects, we’ve added a diode switch to go between two different sets of diodes, or to
disengage the diodes entirely.
The Harmonic Percolator was also the basis for the Catalinbread Karma Suture, which is available in
both germanium and all-silicon versions. The Karma Suture was traced by Aion FX and adapted as the
Calliope Vintage Fuzz.
USAGE
The Particle has the following controls:
• Harmonics controls the signal level coming into the transistor fuzz stage. Its effect is nearly
identical to rolling back the guitar volume.
• Balance is an output volume control.
• Diodes selects between three sets of clipping diodes.

PARTICLE VINTAGE FUZZ 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 51k Metal film resistor, 1/4W Albini specs. Use 220k for stock version. See build notes for more info.
R2 91k Metal film resistor, 1/4W Albini specs. Use 20k for stock version. See build notes for more info.
R3 3M9 Metal film resistor, 1/4W Albini specs. Use 750k for stock version. See build notes for more info.
R4 91k Metal film resistor, 1/4W
R5 4k7 Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W
C1 100pF MLCC capacitor, NP0/C0G
C2 47n Film capacitor, 7.2 x 2.5mm
C3 47uF Electrolytic capacitor, 5mm
C4 2.2uF Electrolytic capacitor, 4mm Albini specs. Use 1uF for stock version. See build notes for more info.
C5 1n5 Film capacitor, 7.2 x 2.5mm Albini specs. Use 1n for stock version. See build notes for more info.
C6 100n Film capacitor, 7.2 x 2.5mm
C7 100uF Electrolytic capacitor, 6.3mm
C8 100n MLCC capacitor, X7R
D1 1N5817 Schottky diode, DO-41
D2 Ge Germanium diode, DO-07 Any NOS germanium diode will work here.
D3 Ge Germanium diode, DO-07 Any NOS germanium diode will work here.
D4 1N914 Fast-switching diode, DO-35
D5 1N914 Fast-switching diode, DO-35
D6 1N914 Fast-switching diode, DO-35
D7 1N914 Fast-switching diode, DO-35
Q1 2N404A Germanium transistor, PNP Original uses 2N404A, available from Small Bear Electronics, but just
about any good germanium transistor will work. See build notes.
Q2 2N3904 BJT transistor, NPN, TO-92 Original uses 2N3565. 2N3904 is a near-exact substitute.
HARM. 100kA 16mm right-angle PCB mount pot
BAL. 50kA 16mm right-angle PCB mount pot
CLIP SPDT cntr off Toggle switch, SPDT on-off-on
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.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

PARTICLE VINTAGE FUZZ 4
BUILD NOTES
Germanium transistor
The original Harmonic Percolator used 2N404A PNP germanium transistors for Q1. These are not
impossible to find on eBay and other vintage parts sellers, and NTE makes a new-production version
with the same part number. But as with most germanium transistors, the exact part number isn’t
important, so don’t spend too much time or money hunting down something that says 2N404A.
You’re looking for something that is low gain (30-50 hFE). The circuit is pretty tolerant of leakage, so
even something with a decent amount of leakage (150-300µA) will work fine.
Many people have used higher-gain transistors in this circuit and liked the result, so if you have a few
different types of germanium transistors, use a socket and experiment with them.
Silicon transistor
The original circuit used 2N3565 NPN silicon transistors for Q2. These are nearly identical to the
2N3904 (“real world” typical hFE range of 180 to 220) so there is absolutely nothing special about
this part. It’s recommended to just use a 2N3904 here, although if you want some extra cosmetic style
points, you can use a metal can silicon transistor such as the 2N2222.
“Albini” specs
The Percolator was perhaps most famously associated with producer & musician Steve Albini as one of
his “secret sauce” effect units. Curiously, his unit seemed to sound different from other Percolators, and
when it was dissected, it was found to have several different values than others that had been traced.
His is the only known unit to use these values.
Because of this, there are really two different versions of the Percolator, the “stock” version and the
“Albini” version. Many people prefer the Albini version, and so those values are provided as the default
configuration for the Particle in the parts list and schematic. However, the alternate values for the
stock version are provided as well. The sounds are very different to the point where they’re almost two
different pedals, so you may want to build both if you’re curious.
Q1 silkscreen
The initial release of the Particle (50 PCBs) had the silkscreen labels for Q1’s emitter and collector
reversed. The left pad is the emitter and the right pad is the collector. The image on page 1 shows how it
should be, labeled E-B-C, corrected in subsequent restocks. If your PCB is labeled C-B-E, the silkscreen
should be ignored.

SCHEMATIC
PARTICLE VINTAGE FUZZ 5
IN
OUT
1N5817
100uF
100kA
50kA
GND
+9V
100n
VA
GND
GND
2N3565
2N404A
100pF
47n
51k
GND
91k
GND
47uF
GND
3M9
91k
1n5
GND
100n
4k7
1N695
1N695
GND
VA
2u2
D1
C7
HARMONICS
1
2
3
BALANCE
1
2
3
C8
Q2
Q1
C1
C2
R1
R2
C3
R3
R4
C5
C6
R5
D2
D3
D4D5
D6 D7
CLIP
2
3 1
C4
GND

PARTICLE VINTAGE FUZZ 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: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: 0, y: +0.66
ø1/4”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
BALANCE HARMONICS
CLIPPING
FOOTSWITCHLED
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN

PARTICLE VINTAGE FUZZ 7
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

PARTICLE VINTAGE FUZZ 8
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT

PARTICLE VINTAGE FUZZ 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
1.0.2 (2022-09-20)
Revised build notes to include additional information on transistor selection.
1.0.1 (2021-03-14)
Added note about Q1’s emitter and collector being mistakenly reversed on the PCB silkscreen.
1.0.0 (2021-02-19)
Initial release.