aion ASTRA SILICON FUZZ User manual

ASTRA SILICON FUZZ 1
PROJECT NAME
ASTRA
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Astrotone Fuzz
An early silicon fuzz from 1966 that was also sold as the Sam Ash Fuzzz Boxx. One of the first drive
circuits to include a tone control.
Silicon fuzz 1.0.1 (2021-04-27)
BUILD DIFFICULTY
Beginner
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

ASTRA 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 Astra Silicon Fuzz is a clone of the Astrotone Fuzz, also released as the Sam Ash Fuzzz Boxx (yes,
there are three Z’s and two X’s!). It was manufactured by the Universal Amplifier Company in New York
City from 1966-1968.
The Astrotone was one of the first silicon fuzz units, developed in an era when germanium transistors
were still widely used. It’s also one of the first effects pedals to feature a tone knob, although it’s not
particularly effective in this circuit (at least not without some modifications) and later fuzz pedals such
as the 3-knob Tone Bender greatly improved upon the concept.
Analogman released his version of the Astrotone, conveniently also called the Astrotone since the
original trademark had expired. It has the exact same topology, but has several component values
changed out to round out the tone and remove the thinness of the original. It’s not an exact clone, but
it’s still very highly regarded. A parts list for the Analogman version is provided in the documentation
alongside the original version.
The updated version of the Astra includes a toggle switch to select between three different sets of
clipping diodes. Since the circuit uses hard clipping with no volume recovery stage afterward, the
clipping diodes will directly impact the maximum available volume.
USAGE
The Astra has the following controls:
• Attack is an input volume control that reduces the gain before the transistor amplification stage,
acting as a drive control.
• Tone cuts the treble after the clipping stage.
• Level controls the overall output of the effect.
• Clip (toggle switch) selects between three sets of diodes: 1x silicon (stock), 2x silicon, and LEDs.

ASTRA 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 1M Metal film resistor, 1/4W Analogman version uses 1.2M here.
R2 22k Metal film resistor, 1/4W
R3 470k Metal film resistor, 1/4W
R4 1M Metal film resistor, 1/4W Analogman version uses 1.2M here.
R5 1k8 Metal film resistor, 1/4W
R6 1k8 Metal film resistor, 1/4W Analogman version uses 470R here.
R7 100R Metal film resistor, 1/4W Power supply filter resistor (not on original unit)
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 Analogman version uses 470n here.
C2 47n Film capacitor, 7.2 x 2.5mm
C3 47n Film capacitor, 7.2 x 2.5mm
C4 47n Film capacitor, 7.2 x 2.5mm Analogman version uses 470n here.
C5 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C6 100n MLCC capacitor, X7R Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
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
D6 1N914 Fast-switching diode, DO-35
D7 1N914 Fast-switching diode, DO-35
D8 5mm LED, 5mm, red diffused Can also use 3mm LEDs.
D9 5mm LED, 5mm, red diffused Can also use 3mm LEDs.
Q1 2N3904 BJT transistor, NPN, TO-92 Original uses 2N3565. 2N3904 is an exact substitute.
Q2 2N3904 BJT transistor, NPN, TO-92 Original uses 2N3565. 2N3904 is an exact substitute.

ASTRA SILICON FUZZ 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
ATTACK 100kB 16mm right-angle PCB mount pot
TONE 10kB 16mm right-angle PCB mount pot
LEVEL 10kB 16mm right-angle PCB mount pot
CLIP SPDT cntr off Toggle switch, SPDT on-off-on
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.

ASTRA SILICON FUZZ 5
BUILD NOTES
Transistor selection
The original Astrotone used 2N3565 transistors, which varied widely in gain. Some batches were in the
180-220 range. similar to the 2N3904, and others were more like 400-500, similar to the 2N5088. The
lower-gain ones were more prevalent.
The exact gain characteristics of the 2N3565 transistors used in the original Astrotone are not known,
but it doesn’t matter too much. The important thing to know is that there is nothing special about the
original vintage transistors. The 2N3904 will sound exactly the same.
Diode selection
Photos of original Astrotone units show that it used DO-7 glass case diodes, which are usually
associated with germanium. However, the original manual for the Astrotone claims it uses all silicon
semiconductors (which includes diodes)—and in the 1960’s when small-signal silicon diodes were first
coming on the market, there were a lot of them in the DO-7 case, since that was the format used by most
diodes. Therefore, while DO-7 silicon diodes are rare today, this would not be uncommon to see in 1966.
The other evidence in favor of them being silicon is more practical: since they’re hard clippers with no
gain recovery afterward, they would directly impact the max volume level. At ~0.3V forward voltage
(typical for germanium), it would clamp the maximum volume at unity or lower, and the original units
would have a hard time achieving unity gain if they were in fact germanium diodes.
So, on balance, we’d conclude that despite looking like germanium didoes, the Astrotone was an early
adopter of silicon diodes. And allowing that they are in fact silicon, the standard 1N914 would be an
exact replacement.
Analogman mods
The Analogman version of the Astrotone uses 1M2 for R1 and R4, 470R for R6, and 470n for C1 and C4.
The vintage version is very thin-sounding, lacking in bass, and these modifications help to round it out.
Even if you stick with the original vintage circuit, you may find it worthwhile to use Analogman’s tone
control modification, which reduces R6 to 470R. All the tones of the original unit are still present except
at the very extreme end of the range.

SCHEMATIC
ASTRA SILICON FUZZ 6
1N5817
100uF
GND
+9V
100n
VA
10kB
GND
10kB
100kB
GND
47n
2N3565
2N3565
1M
22k
470k 1M
1k8 1k8
47n
47n
GND
GND
GND GND
47n
VA VA
VA
GND
100R
1N914
1N914
1N9141N914
1N914 1N914
GND
IN
OUT
D1
C5
C6
LEVEL
1
2
3
TONE
1
2
3
ATTACK
1
2
3
C1
Q1
Q2
R1
R2
R3 R4
R5 R6
C2 C3
C4
R7
D2 D3
D4D5
D6 D7
D8 D9
CLIP
2
3 1
GND

ASTRA 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: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: 0, y: +0.66
ø9/32”
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
LEVEL
CLIPTONE
ATTACK
FOOTSWITCHLED
x: +0.85, y: +0.66
ø1/4”

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

ASTRA 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
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.

ASTRA 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
1.0.1 (2021-04-27)
Removed RPD from parts list which was included by mistake. The schematic and Mouser spreadsheet
were correct.
1.0.0 (2021-03-19)
Initial release.