Aion Electronics PENUMBRA BASS FUZZ User manual

PENUMBRA BASS FUZZ 1
PROJECT NAME
PENUMBRA
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Zvex Woolly Mammoth / Mastotron
A full-frequency silicon fuzz, originally designed for bass but just as suited for guitar. Famously used by
Chris Wolstenholme of Muse.
Bass fuzz 1.0.1 (2019-12-23)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

PENUMBRA BASS 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 Penumbra Bass Fuzz is inspired by the Zvex Woolly Mammoth and Mastotron, taking elements from
each but with some modifications for better usability.
The Woolly Mammoth is a full-frequency fuzz with no low-end cut, making it great for bass, but of
course it works great on guitar as well. It features controls for fuzz level, EQ, pinch (pulse width of the
wave form) and output volume. The Mastotron added a few controls but is otherwise identical.
The Penumbra is a combination of the two, including the Subs (Low) toggle but not the “Relax / Push”
control. This has been replaced by a transformer-based pickup simulator, originally designed by Jack
Orman of AMZ and used by others including Earthquaker Devices in their Erupter pedal.
Like many vintage fuzz circuits, the Woolly Mammoth works best when it’s the first pedal after the
guitar. If its input signal is too low-impedance (i.e. coming from a buffer or an active pedal), it can
drastically change the character of the effect. The pickup simulator will convert any input impedance
into the impedance of a guitar pickup, so the Penumbra will behave as it should no matter where it’s
placed in the chain.
This pickup simulator is on a toggle switch, allowing it to be easily bypassed. This way you can leave it off
if the Mammoth is the first pedal in the chain. When the pickup simulator is turned off, the Penumbra is
sonically identical to the original Woolly Mammoth / Mastotron circuit.
USAGE
The Penumbra has the following controls:
• Fuzz sets the amount of transistor gain and thus the fuzz level of the effect.
• Pinch changes the pulse width of the waveform, from symmetrical square wave on the left, to
asymmetrical on the right. It also affects the amount of gating.
• Tone allows the high-end to be tweaked without sacrificing the bass frequencies.
• Volume is the output volume control.
• Low is a 3-position toggle that changes the output capacitor, which controls the bass EQ.
• Pickup is a pickup simulator that allows the Penumbra to be used anywhere in the effects chain.

PENUMBRA BASS 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
R2 1M Metal film resistor, 1/4W
R3 1M Metal film resistor, 1/4W
R4 1k Metal film resistor, 1/4W
R5 56k Metal film resistor, 1/4W
R6 1k Metal film resistor, 1/4W
R7 2k2 Metal film resistor, 1/4W
R8 22k Metal film resistor, 1/4W
R9 10k Metal film resistor, 1/4W
R10 5k1 Metal film resistor, 1/4W
R11 100R Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W
LEDR 4k7 Metal film resistor, 1/4W
C1 1uF Film capacitor, 7.2 x 3.5mm
C2 1n Film capacitor, 7.2 x 2.5mm
C3 220n Film capacitor, 7.2 x 2.5mm
C4 10n Film capacitor, 7.2 x 2.5mm
C5 100uF Electrolytic capacitor, 6.3mm
C6 100uF Electrolytic capacitor, 6.3mm
C7 10n Film capacitor, 7.2 x 2.5mm
C8 220n Film capacitor, 7.2 x 2.5mm
C9 33n Film capacitor, 7.2 x 2.5mm
C10 68n Film capacitor, 7.2 x 2.5mm
C11 100uF Electrolytic capacitor, 6.3mm
C12 100uF Electrolytic capacitor, 6.3mm
C13 100n MLCC capacitor, X7R
D1 1N5817 Schottky diode, DO-41
Q1 2N5457 JFET, N-channel, TO-92 Any general purpose JFET should be fine here (2N5458, MPF102).
Q2 2N3904 BJT transistor, NPN, TO-92
Q3 2N3904 BJT transistor, NPN, TO-92

PENUMBRA BASS FUZZ 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
XFM1 42TL019 Transformer, audio, 10KCT/600CT Mouser 42TL019-RC
FUZZ 5kC 16mm right-angle PCB mount pot
PINCH 500kB 16mm right-angle PCB mount pot
TONE 10kB 16mm right-angle PCB mount pot
VOL. 10kB 16mm right-angle PCB mount pot
SW1 SPDT cntr off Toggle switch, SPDT on-off-on
SW2 DPDT on-on Toggle switch, DPDT on-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.

PENUMBRA BASS FUZZ 5
BUILD NOTES
Transformer orientation
The 42TM019 transformer is symmetrical, so it can be inadvertently installed backwards, which would
give it the wrong coil resistance for the pickup simulation.
Pin 1 and 6 are marked on the PCB. The side with pin 1 corresponds to the primary coil, which is marked
“P” on the transformer. So in other words, the side marked “P” should be facing toward the SW2 pads.
Bypassing the transformer
With the toggle switch in the “off” position, the transformer is fully out of the circuit. But, if you’re not
able to source the transformer or just don’t want to use it, you can leave it off entirely.
Jumper the two center pads of the toggle switch together (pads 2 and 6) and omit the following parts:
• C1-2
• R1-4
• Q1
• XFM1

SCHEMATIC
PENUMBRA BASS FUZZ 6
GND
2M2
100uF
500kB
5kC
GND
10kB
10kB
+9V
1N5817
2N5457
1uF
1M1M
GND
VA
100R
1M
GND
VA VA
42TL019
1k
1n
GND
220n
2N3904
56k
VA
2N3904
1k
GND
10n
GND
2k2
GND
22k
VA
100uF
GND
100uF
10n
10k
5k1
220n
GND
GND
33n68n
100uF
100n
RPD
C12
PINCH
1
2
3
FUZZ
1
2
3
TONE
1
2
3
VOLUME
1
2
3
IN
OUT
D1
Q1
C1
R1R2
R11
R3
XFM1
1 2 3
456
R4
C2
C3
Q2
R5
Q3
R6
C4
R7 R8
C5
C6
C7
R9
R10
C8
SW1
2
3
1
SW2A
A2
A3
A1
SW2B
B2
B3
B1
C9C10
C11
C13
GND
P
S

PENUMBRA BASS 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: -0.775, y: +1.71 x: +0.775, y: +1.71
ø9/32” ø9/32”
x: -0.775, y: +0.41
ø9/32”
x: 0, y: +0.41
ø1/4”
x: +0.775, y: +0.41
ø9/32”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
FUZZVOLUME
PINCHPICKUP
x: 0, y: +1.06
ø1/4”
LOW
TONE
FOOTSWITCHLED
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN

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

PENUMBRA BASS 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

PENUMBRA BASS 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 (2019-12-23)
Updated drill template - the knobs were spaced too far apart originally.
1.0.0 (2019-08-31)
Initial release.