aion ZIRCON SILICON FUZZ User manual

ZIRCON SILICON FUZZ 1
PROJECT NAME
ZIRCON
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
“Hot Silicon” Tone Bender
An adaptation of the classic Tone Bender Mk. II circuit using silicon transistors and a Big Muff-style tone
control.
Fuzz / Distortion 1.0.0 (2021-02-19)
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.87” (bypass board).
BUILD DIFFICULTY
Easy

ZIRCON SILICON FUZZ 2
TABLE OF CONTENTS
1Project Overview 7Drill Template
2Introduction & Usage 8Enclosure Layout
3-4 Parts List 9Wiring Diagram
5Build Notes 10 Licensing
6Schematic 10 Document Revisions
INTRODUCTION
The Zircon Silicon Fuzz is a version of the “Hot Silicon” community project, itself an adaptation of the
Sola Sound Tone Bender for silicon transistors.
The history of this circuit is a bit suspect, with two people claiming originality. It dates to 2003 at the
very latest when Doug Hammond posted a schematic for a circuit he called the Hot Silicon, which was a
hybrid of two earlier circuits from Gus Smalley and Aron Nelson.
However, an almost identical circuit was posted by Mictester in 2009 on freestompboxes.org, and he
claimed he first developed it in the 1970s when he was trying to make a friend’s silicon Tone Bender
from Macari’s (Sola Sound) sound good, and then tweaked the circuit over the following decades until
arriving at the finalized version in 1994. (Sola Sound did make a very small number of Tone Bender Mk
III’s with silicon transistors—these are different than the Jumbo Tone Bender which was basically a Big
Muff clone.)
Maybe it was just parallel development that arrived at the same outcome. Regardless of true origin,
though, the Hot Silicon (or Silicon Tone Bender) is a fantastic circuit that has endured as a classic in the
DIY scene for many years.
The Zircon is a near-direct adaptation of the Hot Silicon circuit, with one change: the input capacitor
switch (called “Fat” in the original schematic) has been changed to a potentiometer so it can be gradually
blended in or out rather than being either full-on or full-off.
USAGE
The Zircon has the following controls:
• Body blends between two input capacitors. Note that this may be seen as working backwards, with
more bass on the low end that is gradually removed for a treble emphasis on the high end.
• Gain controls the amount of gain in the transistor fuzz stage.
• Tone is a Big Muff-style balance control that pans between a low-pass filter (bass emphasis) and a
high-pass filter (treble emphasis).
• Volume is the overall output level.

ZIRCON SILICON 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 150k Metal film resistor, 1/4W
R2 22k Metal film resistor, 1/4W
R3 10k Metal film resistor, 1/4W
R4 1k Metal film resistor, 1/4W
R5 10k Metal film resistor, 1/4W
R6 100R Metal film resistor, 1/4W
R7 47k Metal film resistor, 1/4W
R8 10k Metal film resistor, 1/4W
R9 10k Metal film resistor, 1/4W
R10 10k Metal film resistor, 1/4W
R11 10k Metal film resistor, 1/4W
R12 2k2 Metal film resistor, 1/4W
R13 100R Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W
C1 10n Film capacitor, 7.2 x 2.5mm
C2 10uF Electrolytic capacitor, 5mm
C3 100n Film capacitor, 7.2 x 2.5mm
C4 4.7uF Electrolytic capacitor, 4mm
C5 100n Film capacitor, 7.2 x 2.5mm
C6 8n2 Film capacitor, 7.2 x 2.5mm
C7 100n Film capacitor, 7.2 x 2.5mm
C8 100uF Electrolytic capacitor, 6.3mm
C9 100n MLCC capacitor, X7R
D1 1N5817 Schottky diode, DO-41
Q1 2N5088 BJT transistor, NPN, TO-92
Q2 2N5088 BJT transistor, NPN, TO-92
Q3 2N5088 BJT transistor, NPN, TO-92
Q4 2N5088 BJT transistor, NPN, TO-92
BIAS 5k trimmer Trimmer, 10%, 1/4" See build notes for bias info.

ZIRCON SILICON FUZZ 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
BODY 100kA 16mm right-angle PCB mount pot
GAIN 1kB 16mm right-angle PCB mount pot
TONE 50kB 16mm right-angle PCB mount pot
VOL. 100kA 16mm right-angle PCB mount pot
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.

ZIRCON SILICON FUZZ 5
BUILD NOTES
Setting the bias trimmer
The bias trimmer sets the gain and saturation of Q3, and is interactive with the external gain control.
It’s recommended to set the external Gain control to halfway, and then adjust the Bias trimmer until the
gating (i.e. the complete cutoff of signal, including background noise, when not playing) goes away. In
other words, you won’t hear this gating effect once it’s biased.
However, this is just a starting point and you may be able to get some interesting sounds by playing with
the bias!
Transistor outlines
Two different sets of footprints have been provided for each of the transistors, either standard TO-92 or
vintage TO-18 metal can (e.g. 2N2222A). Each outline is connected together on the PCB, so you can use
either the top or bottom one in each pair, but not both.

SCHEMATIC
ZIRCON SILICON FUZZ 6
GND
2M2
1N5817
100uF
100kA
1kB
GND
50kB
100kA
+9V
100n
VA
10n
10uF
2N5088
150k22k
VA
GND
10k1k
GND
VA
100n
2N5088
10k
VA
2N5088
100R
GND
47k
5kB
GND
4u7
GND
10k
VA
2N5088
10k
GND
VA
100n
10k
10k
2k2
8n2
GND
100n
GND
GND
100R
RPD
D1
C8
BODY
1
2
3
GAIN
1
2
3
TONE
1
2
3
VOLUME
1
2
3
IN
OUT
C9
C1
C2
Q1
R1R2
R3R4
C3
Q2
R5
Q3
R6
R7
BIAS
1
2
3
C4
R8
Q4
R9
C5
R10
R11 R12
C6 C7
R13
GND

ZIRCON SILICON FUZZ 7
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
VOLUME GAIN
TONE BODY
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”

ZIRCON SILICON FUZZ 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

ZIRCON SILICON FUZZ 9
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT

ZIRCON SILICON FUZZ 10
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 (2021-02-19)
Initial release.