aion Solstice User manual

SOLSTICE AMP DISTORTION 1
PROJECT NAME
SOLSTICE
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Marshall Shredmaster
A great mid-gain amp-like distortion with a 3-band EQ. Most notably used by Jonny Greenwood of
Radiohead and Kevin Shields of My Bloody Valentine.
Overdrive / Amp-Like Distortion 1.0.0 (2018-12-15)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 2.3” x 0.86” (bypass board).

SOLSTICE AMP DISTORTION 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 Solstice Amp Distortion is a recreation of the Marshall Shredmaster, first released in 1991
alongside the Bluesbreaker and the Guv’nor, which was previously released in 1988 as the Drivemaster.
Despite its name, the Shredmaster is not an ultra-gain metal monster like the Boss Metal Zone. Unlike
the Guv’nor, it does have the ability to scoop the mids, so you can get some sounds out of it that
approach the metal territory—but for the most part, the name is misleading.
The Shredmaster has a lot in common with the Guv’nor / Drivemaster, and in fact the first half of both
circuits are nearly identical. However, the Shredmaster has an additional gain recovery stage, and even
though the three tone knobs appear to be the same on the outside, the tone stack is very different.
The Solstice is faithful to the original, but with one added modification: a switch that lets you go
between different clipping diodes. The original has a pretty low clipping threshold with just one 1N914
diode in each direction, meaning its clipping character is more gainy and compressed. But some different
sounds can be coaxed out of it if you stack two additional diodes (as in the Bluesbreaker) or use LEDs (as
in the Guv’nor) to get a higher threshold.
USAGE
The Solstice has the following controls:
• Treble and Bass form a passive 2-band tonestack similar to the type found on an amp. It’s the same
as the classic “FMV” (Fender/Marshall/Vox) arrangement, but with a 1k resistor in place of the mid
knob, essentially fixing the midrange control at a specific setting.
• Contour pans between a mid scoop on one side and a lowpass (treble cut) filter on the other side. It
serves the function of a midrange control while being a little unique in its tone-shaping properties.
• Gain controls the amount of gain in the op-amp gain stages that is fed into the clipping stage.
• Volume controls the overall output of the effect.
• Clipping (toggle switch) selects the clipping diodes which changes the character of the drive tone.

SOLSTICE AMP DISTORTION 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 3k3 Metal film resistor, 1/4W
R3 9k1 Metal film resistor, 1/4W Nearest common value. The original has two 4.7k resistors in series.
R4 680k Metal film resistor, 1/4W
R5 10k Metal film resistor, 1/4W
R6 6k8 Metal film resistor, 1/4W
R7 1k Metal film resistor, 1/4W
R8 47k Metal film resistor, 1/4W
R9 220k Metal film resistor, 1/4W
R10 100R Metal film resistor, 1/4W
R11 33k Metal film resistor, 1/4W
R12 33k Metal film resistor, 1/4W
R13 100k Metal film resistor, 1/4W
R14 100k Metal film resistor, 1/4W
R15 1M Metal film resistor, 1/4W
R16 47k Metal film resistor, 1/4W
R17 47k Metal film resistor, 1/4W
RPD 2M2 Metal film resistor, 1/4W Input pulldown resistor. Can be as low as 1M.
LEDR 4k7 Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 10n Film capacitor, 7.2 x 2.5mm
C2 100pF MLCC capacitor, NP0/C0G
C3 47n Film capacitor, 7.2 x 2.5mm
C4 68n Film capacitor, 7.2 x 2.5mm The original has 220n and 100n capacitors in series, which makes 68n.
C5 47pF MLCC capacitor, NP0/C0G
C6 100n Film capacitor, 7.2 x 2.5mm
C7 22n Film capacitor, 7.2 x 2.5mm
C8 220n Film capacitor, 7.2 x 2.5mm
C9 22n Film capacitor, 7.2 x 2.5mm
C10 220n Film capacitor, 7.2 x 2.5mm
C11 2n2 Film capacitor, 7.2 x 2.5mm

SOLSTICE AMP DISTORTION 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
C12 100n Film capacitor, 7.2 x 2.5mm
C13 47n Film capacitor, 7.2 x 2.5mm
C14 1n Film capacitor, 7.2 x 2.5mm
C15 220n Film capacitor, 7.2 x 2.5mm
C16 1n Film capacitor, 7.2 x 2.5mm Try 470pf or 330pf here to reduce the steep treble cut. See build notes.
C17 220n Film capacitor, 7.2 x 2.5mm
C18 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C19 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C20 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 3mm LED, 3mm, red diffused
D9 3mm LED, 3mm, red diffused
IC1 TL072 Operational amplifier, DIP8
IC1-S DIP-8 socket IC socket, DIP-8
IC2 TL072 Operational amplifier, DIP8
IC2-S DIP-8 socket IC socket, DIP-8
TREBLE 25kB 16mm right-angle PCB mount pot
BASS 100kA 16mm right-angle PCB mount pot
CONT. 100kB 16mm right-angle PCB mount pot
GAIN 100kB 16mm right-angle PCB mount pot
VOL 100kA 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.

SOLSTICE AMP DISTORTION 5
BUILD NOTES
Clipping switch
The clipping switch allows you select between different sets of diodes.
The downward position of the toggle switch is the stock Shredmaster clipping arrangement, which has
one silicon diode in each direction. The upward position of the toggle is two diodes in each direction, a
higher clipping threshold with a more open sound. The center position leaves only the LEDs for a more
dynamic and transparent tone.
If you look at the schematic, you’ll see that the LEDs, D8 and D9, are always connected. However, in
either the up or down switch positions, the lower-threshold diodes are connected and so the LEDs have
no effect—there’s no signal remaining for them to clip.
Feel free to experiment, For example, you could jumper D7 for asymmetrical clipping. Or, you could omit
the two clipping LEDs for a diode-lift mode in the center position.
Treble cut capacitor
Many people feel that the biggest flaw with the stock Shredmaster is the steep treble cut introduced
near the end. C16 is a 1nF capacitor that forms a low-pass filter right before the volume control and is
solely responsible for this cut. The common consensus is that the circuit will perform much better if this
capacitor is dropped down to 330pF or 470pF to allow more treble through this stage.
Schematic notes
If you search online for Shredmaster schematics, you could pull up five of them and each one would
probably be slightly different. Early traces of the pedal were all over the map, and there was especially a
lot of confusion surrounding the portion near C4 and R3 where the effect was grounded in bypass mode.
The two capacitors and two resistors in series should be simplified down in a true-bypass setup, but it
was often not done correctly.
The correct schematic is the one in this post from FSB. From here you can see why the different values
were circulating around. The series value of C15 and C6 (using the PhnomPenh2004 schematic’s
numbering), 220n in series with 100n, is 68n. So some schematics correctly show the capacitor as 68n,
while others show it as 220n, dropping the second capacitor entirely. Some DIY Shredmaster projects
maintain both capacitors, but this is really not necessary at all—especially since 68n is a standard value
and easy to find.
Some schematics show 4.1k for R7 and R8 (again, using the PhnomPenh2004 schematic numbering)
for 8.2k total. It’s possible that some variants used this value. However, the unit shown in the photos is
definitely 4.7k. Two of these in series is 9.4k total, with 9.1k being the nearest common value. 10k is also
fine if that’s all you have—it basically just reduces the minimum gain setting by a tiny amount.
Another common discrepancy is R1, the 47k resistor in the second-to-last op-amp stage (R8 in this
project). Some schematics show this as 39k. It’s possible that some versions of the pedal used 39k there,
but based on the photos in the FSB thread, it’s definitely 47k in that unit.

SCHEMATIC
SOLSTICE AMP DISTORTION 6
GND
2M2
1N5817
100uF
GND
+9V
100n
VA
3k3
9k1
680k
10k
1M
47k
47k
10n
TL072P
100pF
47n
GND
100kB
TL072P
68n
47pF
100n
100kA
47uF
GND GND
1M
220n
GND
22n
6k8
220n
22n
25kB100kA
1k
TL072P
TL072P
220n
47k
220k
2n2
100R
100n
33k 33k
100kB
47n
1n
220n 100k
100k
1n
GND
GND
VB
VB
VB
VB
VB
VB
VB
VB
VB
VA
VA
VB
RPD
D1
C18
IN
OUT
C20
R2
R3
R4
R5
R1
R16
R17
C1
IC1A
2
3
1
C2
C3
GAIN
1
2
3
IC1B
6
5
7
84
C4 C5
C6
1
2
3
VOLUME
C19
R15
C17
D2 D3
C7
R6
C8
C9
TREBLE
1
2
3
BASS
1
2
3
R7
IC2A
2
3
1
IC2B
6
5
7
84
C10
R8
R9
C11
R10
C12
R11 R12
1
2
3
CONTOUR
C13
C14
C15 R13
R14
C16
D4 D5
CLIP
2
3 1
D6D7
D8
D9
GND

SOLSTICE AMP DISTORTION 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 requires the use of closed-frame jacks like the Switchcraft 111X. Open-frame jacks will
not fit in layouts with 5 or more knobs due to the placement of the DC jack.
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: +1.71
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
TREBLEBASSCONTOUR
GAINCLIPVOLUME
FOOTSWITCHLED
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN

SOLSTICE AMP DISTORTION 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

SOLSTICE AMP DISTORTION 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.

SOLSTICE AMP DISTORTION 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 (2018-12-15)
Initial release.