Aion Electronics Blueshift Chorus User manual

1BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
WARNING / DISCLAIMER
PLEASE READ THE FOLLOWING BEFORE PURCHASING OR BUILDING THIS PROJECT!
1. NO DIRECT TECHNICAL SUPPORT: This project has been veried to be working. I have done my best
to provide extremely thorough documentation, including information to help you troubleshoot. But on a
project this size, I have to reiterate that Aion Electronics cannot provide direct technical support for this
project or others. I love helping people bring these circuits to life, but my availability is very limited. If you post
your question on one of the DIY forums and send me a link, I will do my best to chime in. Just know before
purchasing this PCB that there is no implied guarantee of the nal product, because the biggest factor is
outside my control: you! Your experience and your attention to detail are the most important ingredients in
making sure this works. My role is to provide the recipe and some cooking utensils.
2. IT WILL TAKE AWHILE: Be prepared to invest some hours into putting this together. You’ll want to be
doubly careful when populating the board since it’ll be much more di󰀩cult to track down a problem if you were
to make even the most basic of mistakes (for instance, accidentally using a 100k resistor somewhere instead
of a 10k). You can’t be too cautious. I’d recommend measuring each resistor with a multimeter before putting
it into place. Triple-check your wiring. The more time you spend on the initial build, the less time you’ll have to
spend troubleshooting.
3. IT’S COMPLICATED: This is a very complex circuit in a very small enclosure and it takes experience and a
lot of attention to detail in order to pull it o󰀨. Hopefully it goes without saying, but if you’ve never built a guitar
pedal before, this shouldn’t be your rst. If you haven’t successfully built at least ten or fteen, including a
few choruses or delays, you may not be ready for this one yet.
4. YOU’VE GOT TO BUILD IT AS IT WAS INTENDED: I approached the project as though I was designing a
completed product for market. Everything has been designed to be built using methods you’d see in a high-end
pedal (for instance, PCB-mounted switches, a stando󰀨 for mounting stability, and components with specic
sizes and characteristics) and a full bill of materials has been provided so that it is very easy to order all the
parts from Mouser. We all build pedals in our own style, but with this one, if you try to “freestyle” by doing
your own enclosure layout or using parts other than the ones specied, you might back yourself into a corner.
Please do things my way—you’ll end up with a very professional and durable end product and you might even
learn a few things in the process!
5. IT’S NOT CHEAP: Between the PCB, enclosure, hardware, potentiometers, and the on-board components,
expect to spend a minimum of $100 USD and probably closer to $125. Please don’t try to cut corners on the
parts selection by using poor-quality components or by substituting “close enough” components that you have
laying around. You’re putting a lot of time and e󰀨ort into this build, so it’s worth a few extra dollars to use the
right parts. Expect to order from more than one web store to get everything you need.
6. IT NEEDS TO BE BIASED: This pedal will not function properly without biasing the BBDs. It can be done by
ear with passable results, but for optimum sound quality and noise control, it requires an oscilloscope. If you
don’t have one, be prepared to either buy one or to make friends with someone who does own one.
Now that you’ve been properly warned: on to the fun stu󰀨!

2BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Blueshift Chorus
BOSS DC-2 Dimension C
See pg. 8 for a larger image of the PCB layout.
This is a faithful clone of the BOSS DC-2 Dimension C, widely regarded as the best stompbox chorus ever
made as well as being one of the most coveted Boss pedals out there. Originally manufactured from 1985 to
1989, it was a guitar pedal adaptation of the revered Roland SDD-320 Dimension D rack unit.
It’s di󰀨erent from other choruses in that there are actually two clock+BBD pairs, each powered by either the
inverted or non-inverted output of a single LFO. These BBDs then modulate the dry signal so that signal “A”
reaches its maximum delay time when signal “B” reaches its minimum and vice versa. Since the average
remains constant, this e󰀨ect is referred to as motionless because it doesn’t have the signature “warble” or
unsteadiness of a traditional chorus with a single BBD.
Table of contents
Blueshift Project LinkOverview
1. Warning / Disclaimer
2. Intro / Overview
3. Usage instructions;
di󰀨erences from original circuit
4. Parts
5. Parts continued; part notes
6. Part notes; parts spreadsheet
7. Adjustments & calibration
8. Adjustments & calibration, cont.
9. Schematic
10. Enclosure drill template
11. PCB layout close-up
12. Enclosure layout
13. Enclosure wiring, standard bypass
14. Enclosure wiring, mininmalist bypass
15. Bypass methods overview
16. General build instructions
17. Build checklist; disclaimer & licensing

3BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Usage
On one end of the guitar pedal spectrum, you’ve got something like the Fuzz Factory where half of the
components in the circuit are potentiometers and you have far more control over the device than you could
ever want. The DC-2 is the very opposite: it has an obscene number of parts crammed into a small box and
you only get three toggle switches to control it.
Because of this, usage is pretty basic: just plug in a guitar, send the output to either one amp or two, and
ip the toggle switches until you like the sound. In general, the lower presets are more subtle and the higher
presets are more noticeable, but it doesn’t ever get too extreme.
Stereo operation
The DC-2 was designed to accept a mono input and split it into stereo, with one BBD controlling each side of
the stereo signal. However, the unit can also mix the signal back down to mono if you are not running a stereo
conguration.
If you have a cable plugged into output “B”, the signal will be split into stereo between “A” and “B”. If nothing is
plugged into output “B”, the signal will be summed to mono.
Di󰀨erences from the original circuit
The Blueshift is faithful to the original Dimension C circuit, with only the following changes.
Radio buttons
The original unit had what are called “radio” buttons, meaning that when a button is pressed, it pops all of the
others up so that only one can be down at a time. Since these radio buttons are highly customized and outside
the reach of DIYers, I converted them to toggle switches.
The function is the same, but you’ll notice there are only three of these switches while the original unit has
four. This is because the rst button on the DC-2 does not actually connect anything—it only resets the other
buttons. Accordingly, in the Blueshift, if all of the toggles are down (o󰀨) then that is the equivalent of preset 1. If
the rst toggle is up, that’s preset 2, and so on.
The advantage of this setup over the original is that you can combine the modes to produce a total of seven
di󰀨erent settings.
Bypass
The original unit uses the standard BOSS ip-op bypass. The Blueshift has been designed to use a stomp
switch and opto-FET in a conguraton that allows you to choose from two di󰀨erent bypass options. The rst
method mimics the signal path in the original, while the second method only passes the signal through a single
op-amp bu󰀨er before splitting it into e󰀨ect and output.
See page 15 for more information on these bypass methods.

4BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Parts
Resistors
R1 1M
R2 100k
R3 10k
R4 10k
R5 1M
R6 10k
R7 47k
R8 10k
R9 100k
R10 33k
R11 2k2
R12 68k
R13 10k
R14 10k
R15 10k
R16 100k
R17 10k
R18 10k
R19 10k
R20 680k
R21 680k
R22 56k
R23 10k
R24 10k
R25 10k
R26 10k
R27 10k
R28 10k
R29 10k
R30 100R
R31 100R
R32 100k
R33 33k
R34 100k
R35 100k
R36 330k
R37 180k
R38 22k
R39 33k
R40 10k
R41 1k5
R42 8k2
Resistors
R43 6k8
R44 4k7
R45 47k
R46 100k
R47 5k6
R48 47k
R49 4k7
R50 100k
R51 47k
R52 100R
R53 100R
R54 5k6
R55 8k2
R56 1k5
R57 6k8
R58 10k
R59 10k
R60 10k
R61 100k
R62 10k
R63 10k
R64 10k
R65 10k
R66 10k
R67 680k
R68 56k
R69 680k
R70 10k
R71 33k
R72 1k
R73 100k
R74 10k
R75 47k
R76 47k
R77 10k
R78 100k
R79 1k
R80 180K
R81 180K
R82 47k
R83 33k
R84 33k
Resistors
R85 47k
R86 39k
R87 220k
R88 220k
R89 1M
R90 1M
R91 1M
R92 33k
R95 3k9
R97 470k
R98 82k
R99 220k
ICs
IC1 OPA2134 1
IC2 NE570/571 2
IC3 MN3207 3
IC4 MN3102 3
IC5 TL072
IC6 TL072
IC7 TL022
IC8 MN3102 3
IC9 MN3207 3
IC11 NE570/571 2
IC12 OPA2134 1
OPTO H11F1
RG1 78L06
Transistors
Q2 2N5088
Q3 J113
Q4 2N5088
Q5 2N5088
Q6 2N5088
Q7 2N5087
Q8 2N5087
Q9 2N5088
Q10 2N5088

5BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Parts
Capacitors
C1 100uF electro
C2 47n
C3 47uF electro
C4 47n
C5 4n7
C6 1uF lm
C7 1uF lm
C8 100pF MLCC
C9 10uF electro
C10 0.47uF tantalum
C11 22n
C12 100pF MLCC
C13 10uF electro
C14 10uF electro
C15 10uF electro
C16 1n
C17 1uF lm
C18 100pF MLCC
C19 10uF electro
C20 1n8
C21 220pF MLCC
C22 470pF MLCC
C23 220pF MLCC
C24 1n8
C25 470pF MLCC
C26 22n
C27 1uF lm
C28 10uF electro
C29 4u7 bipolar electr.
C30 220n
C31 1uF electro
C32 100pF MLCC
C33 10uF electro
Capacitors
C34 10uF electro
C35 100pF MLCC
C36 47uF electro
C37 10n
C38 10uF electro
C39 1uF lm
C40 100n MLCC
C41 100n MLCC
C42 22n
C43 470pF MLCC
C44 1n8
C45 220pF MLCC
C46 10uF electro
C47 0.47uF tantalum
C48 0.47uF tantalum
C49 1uF lm
C50 47pF MLCC
C51 4n7
C52 4n7
C53 47pF MLCC
C54 1uF lm
C55 3n3
C56 1n2
C57 1n2
C58 3n3
C59 18n
C60 18n
C61 100pF MLCC
C62 18n
C63 1uF lm
C64 1uF lm
C65 1uF electro
Potentiometers
TR1 100k (3362P)
TR2 100k (3362P)
Switches
MODE2 SPDT toggle 4
MODE3 DPDT toggle 4
MODE4 DPDT toggle 4
Diodes
D1 1N4002
D3 1N5225
D4 1N5225
D5 1N914
D6 1N914
D7 1N914
D8 1N914
LED 5mm or 3mm
Jacks
IN 111X
OUT A 111X
OUT B 112BX (TRS)
DC JACK miniature 5
Other hardware
0.625” hex stando󰀨, 6-32 thread (qty 1): This is used to secure the PCB to the enclosure so that stress is not
placed on the solder joints of the toggle switches.
1/4-40 hex nut (qty 6): These are used to space the inside nuts of the toggles to match the stando󰀨.
6-32 x 3/8” pan head screw (qty 2): This is used to secure the PCB and enclosure to the hex stando󰀨.6
Pin headers: These are required, but there are a couple of options. See next page for details.

6BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
1 Dual op-amps: The original DC-2 uses SIL op-amps for layout purposes, all of which are obsolete. Since
IC1 and IC12 are in the signal path, you’ll want to use op-amps that are designed specically for audio. The
OPA2134 is a great choice, but a regular TL072 should do ne as well.
2Compander: The NE570 and NE571 companders (both ICs are cross-compatible) are out of production
in DIP format. They can still be found NOS, the NE570 being much more common, but if you’d rather use
something that is new and in production, the CoolAudio v571 clone is available from Small Bear Electronics.
3Clocks and BBDs: The original DC-2 uses the MN3207/MN3102 combination for the BBDs and clocks.
These are out of production but can still be obtained relatively cheaply. However, you can also opt for one of
two current-production BBD+clock pairs, the CoolAudio v3207/v3102 or the Belling BL3207/BL3102. Both of
these are available at Small Bear Electronics.
4Toggle switches: The toggle switches must have at least a 0.35” (8.89mm) bushing. This is the most
common bushing length, but a few from Mouser’s “Mountain Switch” brand do have a shorter 0.28” (7.1mm)
bushing. This shorter bushing will not allow enough space for the top PCB to clear the jacks.
5DC jack: This project uses a miniature unswitched DC jack like this one from Small Bear Electronics
(available from several other suppliers as well). You can probably t a standard-sized DC jack here—the cutout
on the top PCB is wide enough—but the main issue will be the clearance above the bottom PCB. There’s very
little margin for error, such that even the height of the solder on the pads on the bottom PCB will be a factor.
6Screws: If you have a countersink drill bit, you can countersink the hole on the face of the enclosure and use
a at-head screw on the outside so it’s level with the enclosure. This is purely cosmetic. If you choose to use
the countersink method, you’ll want a 6-32 x 1/4” at head screw for this.
Pin headers
The two PCBs are connected by pin headers: three 3-position headers and one 5-position header. In order to
have enough clearance between the PCBs, the female headers must be at least 0.325” (8.25mm) in height
when mounted to the PCB. Tayda Electronics has them for about 5 cents each, and in my experience they
connected more tightly than the ones from Mouser. Their 5-pin header is here and the 3-pin header is here.
Mouser carries a 5-pin header in the correct height, but not a 3-pin. So if you want to order from Mouser, you’d
be better o󰀨 getting one 16-pin header that snaps apart. Use a razor blade to separate these—if you try to
snap them apart by bending them, the plastic housing will often crack. You’ll need 14 of the 16 sockets.
You’ll also need the male pin headers as well, the type with pins on both ends. Mouser has one here and
Tayda has one here. Tayda is signicantly cheaper and the quality is the same.
MN3007 and MN3101
The Blueshift does not support the MN3007/MN3101 chipset. These ICs require a minimum 9V supply voltage.
Since the DC-2 circuit uses a regulated voltage from the main supply for the BBDs, and regulators typically
require about 2V of headroom to function, 7V is as high as we can reasonably get from a 9V source. The
original Dimension D rack unit ran at a much higher voltage and was able to use the MN3007/MN3101, but it’s
just not possible with the DC-2 circuit as it is. They also use a di󰀨erent pinout.
Mouser parts spreadsheet
Since this is such a complicated build, I created a spreadsheet of parts that can be imported directly to Mouser.
Over 95% of the parts can be obtained from Mouser and their prices are great. I spent a great deal of time
selecting the parts, and the PCB layout is designed around them, especially the boxed lm & electrolytic
capacitors, so by using this spreadsheet to order, you know you are getting the best possible result.

7BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
For international DIYers, Mouser recently upgraded their international shipping options, so it’s very likely that
you will be able to get free shipping with a project this size. Their prices are very competitive as well.
The BOM does assume you have zero parts on your bench, so you may be able to save a few dollars by
comparing the spreadsheet with what you’ve got already and removing what you don’t need, especially things
like the IC sockets. But just know that while it may save a little bit of money to use your own, I guarantee it will
save a lot of potential mistakes to receive them all in labeled bags!
With that said, I have to give the disclaimer that this spreadsheet is being provided only as a convenience.
You are responsible for checking through the parts to make sure they are the ones you want, and Mouser
is responsible for sending you the correct parts. I tried to pick high-availability components from well-known
manufacturers that are stocked in large quantities, but with 70 di󰀨erent parts, it’s likely that one or two of them
will be out of stock at any given time. You will have to nd your own replacements if that happens.
Calibrating
In order to get the highest amount of headroom out of the unit, you’ll need to adjust the trim pots using a signal
generator and an oscilloscope. If you don’t have an oscilloscope, you can get pretty close just adjusting by ear.
Most BBDs do not handle signal symmetrically, so the point of highest headroom is not generally going to be at
the halfway point of the supply voltage like it would be with op-amps. And BBD manufacturing processes were
not very precise, so the circuit must be tuned to the exact BBDs being used.
Whether you do or don’t use an oscilloscope, the rst step is to trim the BBD’s bias voltage to half of the
supply voltage. This sets the starting point for the calibration. The regulated supply for the BBD section
should be around 6.8V, so you’ll want to adjust the trimmers until you read 3.4V on pin 3 of each BBD. This can
be done on just the bottom PCB without the top PCB being attached as long as the unit is powered. It can even
be done before you solder the toggle switches in place.
TR1 adjusts IC9 and TR2 adjusts IC3.
Calibrating without an oscilloscope
While not as accurate as using an oscilloscope, setting the bias voltage by ear will lend good results that
should be enough for most usage. It’s pretty basic: you just want to adjust the two trimmers until you have the
least amount of distortion in the audio signal. However, it’s not very easy to hear, and you certainly won’t be
able to get it tuned with the same level of accuracy if you use an oscilloscope.
So, without an oscilloscope, your best bet is to just set the voltage to the average of di󰀨erent BBDs that have
been tested, then adjust from there if you can hear audible distortion. I came up with a spreadsheet that will be
periodically updated as people send me their voltages.
In my testing (which involved measuring an original DC-2 as well as testing the di󰀨erent brands of BBDs in the
Blueshift), the optimum bias point was always between 3.3V and 3.8V.
Calibrating with an oscilloscope & signal generator
This assumes you know how to operate a signal generator and an oscilloscope and know how to interpret the
readings. If you don’t have one or don’t know how to use one, please use the earlier “Calibrating without an
oscilloscope” section. If you’re planning on building the DC-2 for someone else in any kind of quantity, though,
please do invest in an oscilloscope—you shouldn’t be selling your work if it’s not been professionally calibrated!
Here is how to set the bias using an oscilloscope.
1. If the unit is wired up inside the enclosure, make sure it’s set to “On” using the footswitch. If the unit is not
yet wired up, you’ll need connect pad “N” to ground to turn on the optocoupler. (This is the same for either
bypass method, but the jumpers on the optocoupler need to be set already.)

8BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
2. Set the signal generator to output an 8 kHz sine wave at 2V peak-to-peak. Feed this signal into the pad
marked “A” (circuit input), taking care to connect the signal generator’s ground wire to a common ground.
3. Connect the oscilloscope probe to the pad marked TP1, taking care to connect the ground wire of the
probe to a common ground.
4. Adjust TR1 until the positive and negative halves of the waveforms are symmetrical. They will not be a
pure sine wave like the input, but they should be rounded o󰀨 in about the same shape as each other.
5. Repeat this process with TP2 and TR2.
What type of oscilloscope should you use?
I use and recommend the LabNation SmartScope, a relatively inexpensive (USD $230) software-based
oscilloscope that also includes signal generation functionality. The hardware connects via USB, and you can
use a computer, smartphone or tablet to control it and view the display output. I haven’t used it extensively, but
it has gotten excellent reviews from others and denitely did what I needed it to for this project. There are a few
tutorials and videos available online if you want to see more about it.
What should the waveform look like?
Here is a sample waveform taken from a test point on a real DC-2 unit. This is a screenshot from the
LabNation SmartScope software. The voltage range is set to 1V and the timebase range is set to 50μs. Notice
that the waveforms are symmetrical between top and bottom, but that they are not a perfect sine wave. They
are ever-so-slightly lopsided toward the right side of the wave.

9BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Schematic
+7V
A
B
J I
L K
P
O
M
G H
F
D E
C
N
+9V
3k9
5MM
1N4002
100uF
GND GND
10k
10k
GND
78L06
1N914
GND
100n
+9V
GND
100n
GND
47uF
GND
100R
100R
10uF10uF
GND GND
VA
VB
VR
VC
NE570
NE570
MN3207 MN3102
GND
VC
MN3207 MN3102
GND
VB
10k47n
1M
VR
OPA2134
OPA2134
4n710k
47k
33k
VR
100pF
100k
+9V
10uF
0.47uF
GND GND
1N5225
1N5225
10uF
1n
10uF
GND
100pF
10k10k
GND
1uF
10k
100k
10k10k
10k
VR
470pF 220pF
2N5088
+9V
GND
1n8
GNDGND
TL022
TL022
330k
100k
100k
180k
33k
10n
22k
VA
10k10k
47uF
GNDGND
33k
470k 220k
82k
TL072
TL072
TL072
TL072
47k
47k
47k
5k6 5k6
4k7
GND
100k
GND
VA
100R
10uF
GND
4k7
GND
100k
GND
VA
100R
10uF
GND
2N5087
8k2
1k5
10k
GND
6k8
100pF
GND
1N914
2N5087
8k2
1k5
10k
GND
6k8
100pF
GND
1N914
GND GND
10k
680k
10k10k
10k
470pF 220pF
2N5088
+9V
GND
1n8
GNDGND
22n
680k
GND
56k
10k
680k
10k10k
10k
470pF 220pF
2N5088
+9V
GND
1n8
GNDGND
22n
680k
GND
56k
100k
10uF
+9V
GND
0.47uF
0.47uF
GND
GND
10uF
100pF
100pF
GND
GND
10uF
100kB
VC
GND
2N5088
10k
GND
+9V
10k
100k
100kB
GND
2N5088
10k
GND
+9V
10k
VB
OPA2134 OPA2134
47pF
10k
4n7
47k
33k
100k
1k
GND
VR
47pF
10k
4n7
47k
33k
100k
1k
GND
VR
3n3
3n3
180K
33k47k
39k 220k
1n2
18n18n
180K
33k
47k 220k
1n2
18n
J113
68k 2k2
22n
2N5088
10k
1M
GND
GND
+9V VR
1M
100k
47n
GND
+9V
1N914
1M 1M
VRVR
+9V
GND
VB
GND
VC
4u7
H11F1
220n
GND
A
A A
1uF1uF
1uF 1uF
1uF 1uF
1uF
1uF
1uF
1uF
+9V +9V
+9V
IN
OUT_R
R95
LED
D1
C1
A2
A3 A1
MODE3A
B2
B3 B1
MODE3B
A2
A3 A1
MODE4A
B2
B3 B1
MODE4B
R4
R3
GND
VI
3
2
VO 1
RG1
D8
04C14C
C3
R31
R30
C28 C38
IC2
1
2
3
4
5
6
7
8 9
10
11
12
13
14
15
16
IC11
1
2
3
4
5
6
7
8 9
10
11
12
13
14
15
16
1
2
3
4 5
6
7
8
IC3
1
2
3
45
6
7
8
IC4
1
2
3
4 5
6
7
8
IC9
1
2
3
45
6
7
8
IC8
R6 C4
R5
2 3
1
IC1A
6 5
7
IC1B
C5 R8
R7
R10
C8
R9
C9
C10
D3
D4
C15
C16
C14
C18
R14R15
C7
R25
R16
R26 R27
R28
12C22C
Q5
C20
2 3
1
IC7A
6 5
7
IC7B R36
R35
R34
R37
R33
C37
R38
R59R60
C36
R39
R97 R99
R98
2
3 1
MODE2
2 3
1
IC5A
6 5
7
IC5B
2 3
1
IC6A
IC6B
6 5
7
84 84
R45
R48
R51
R54 R47
R49
R50
R53
C34
R44
R46
R52
C33
Q7
R42
R41
R40
R43
C32
D6
Q8
R55
R56
R58
R57
C35
D7
R66
R67
R65 R64
R70
54C34C
Q10
C44
C42
R69
R22
R19
R20
R18 R17
R24
32C52C
Q4
C24
C26
R21
R68
R32
C19
C48
C47
C46
C61
C12
C13
TR2
1
2
3
Q6
R23
R29
R61
TR1
1
2
3
Q9
R63
R62
OUT_L
2 3
1
IC12A IC12B
6 5
7
C50
R74
C51
R75
R71
R73
R72
C53
R77
C52
R76
R92
R78
R79
C55
C58
R80
R84R82
R86 R87
C56
C62C59
R81
R83
R85 R88
C57
C60
Q3
R12 R11
C11
Q2
R13
R89
OUT_R_RING
R1
R2
C2
D5
R90 R91
C29
OPTO
1
24
6
C30
OPT_IN
OPT_OUT
C49C54
C63 C64
TP2
TP1
C31 C65
C27
C17
C39
C6

10BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Drill Template
Print this page and cut out the drilling template below. Tape it to the enclosure to secure it while drilling. Note
that the holes are shown slightly smaller than they need to be, so drill out the holes as shown and then step up
until they are the correct size for the components. The enclosure layout doesn’t leave much room for error,
so make sure you are very precise in your drilling!
OUT B
2
3
4
OUT A IN
(MONO)

11BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
These are shown 50% bigger than life size. The PCB on the left (the clock + LFO board) measures 2.15” x
2.9”. The PCB on the right (the signal board) measures 2.15” x 3.79”. They are shown here with component
sides facing up, but component sides will face down when installed in the enclosure.
PCB Layout

12BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Enclosure Parts Placement / Layout
This shows the placement of the jacks, switches, and other hardware, looking in from the bottom.
125B
The in/out jacks are Switchcraft 111X for “In” and “Out A” and 112BX for “Out B”. Clones of these can be
found pretty easily and will work ne—but they must be the black box-style enclosed jacks, not the open-frame
type (Switchcraft 11 / 12B) or Neutrik NMJ series.
The DC jack is an unswitched miniature 2.1mm jack like this one from Small Bear Electronics.
Toggle switches are standard Taiway / Mountain Switch toggles (or equivalent) with at least 0.35” bushing.
No other hardware has been tested, so you’re on your own for measuring the t if you use anything else!

13BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Wiring Diagram – Stock Bypass Version
In this wiring diagram, pads C and F are left unconnected. Pads D & E and G & H are jumpered.
Make sure to cross-reference this diagram with the table on page 15. The wires can be pretty hard to follow in
the diagram since it is a small enclosure and there are a lot of layers.
SHIELD
RING
TIP
SHIELD TIP
TIP
+9V
GND
I
J
K
L
N
O
P
M
A B C D E F G H

14BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Wiring Diagram – Minimalist Bypass Version
In this wiring diagram, pads I & J and K & L are jumpered.
Make sure to cross-reference this diagram with the table on page 15. The wires can be pretty hard to follow in
the diagram since it is a small enclosure and there are a lot of layers.
SHIELD
RING
TIP
SHIELD TIP
TIP
+9V
GND
I
J
K
L
N
O
P
M
A B C D E F G H

15BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Setting the bypass method
The bypass method must be set by using jumpers on the optocoupler and following the
corresponding wiring diagram. The diagrams to the left show the jumper positions for each
bypass mode. It’s easiest to set these on the top (non-component) side of the board. The
silkscreen on the PCB shows the jumpers in “Stock” mode.
The stock bypass option mimics the signal path of the original circuit, with the signal passing
through pre-emphasis and de-emphasis lters.
The minimalist bypass option splits the signal immediately after the rst op-amp. The bypass is
still bu󰀨ered for the stereo output, but the signal only passes through that single op-amp bu󰀨er.
Since this is a stereo-splitting e󰀨ect, I’ve intentionally not accounted for true bypass. Passive
signal-splitting can be very problematic unless you know what’s going on in your signal chain.
With that disclaimer, you can probably wire it up as true bypass without too much trouble as long
as you have a 4PDT stomp switch—but you’re on your own if you do! I haven’t tested this and it is
beyond the scope of this documentation.
Since there are a lot of wires in multiple layers inside a small box, the wiring diagrams on pages 13 and 14 can
be a little hard to follow. Use the table below and cross-reference it with the corresponding wiring diagram.
Pad Description Stock Bypass Minimalist Bypass
A Circuit input Input jack tip Input jack tip
B Ground Star ground point Star ground point
C Channel B bu󰀨er send No connection Switch lug 3
D Channel B e󰀨ect send Jumper to pad E Switch lug 1
E Channel B switched output return Jumper to pad D Switch lug 2
F Channel A bu󰀨er send No connection Switch lug 6
GChannel A e󰀨ect send Jumper to pad H Switch lug 4
H Channel A switched output return Jumper to pad G Switch lug 5
I Channel A pre-IC switch return Switch lug 5 Jumper to pad J
J Channel A pre-IC switch send Switch lug 4 Jumper to pad I
K Channel B pre-IC switch return Switch lug 2 Jumper to pad L
L Channel B pre-IC switch send Switch lug 1 Jumper to pad K
M Channel B ring “B” output jack ring B output jack ring
NOptocoupler LED switched ground Switch lug 7 Switch lug 7
O Channel B output “B” output jack tip “B” output jack tip
P Channel A output “A” output jack tip “A” output jack tip
+9V Supply voltage (bottom board) DC jack DC jack
GND Ground (bottom board) Star ground point Star ground point
The stomp switch lugs use the standard numbering system, shown in this diagram:
1
2
3
4
5
6
7
8
9
STOCK
MINIMAL

16BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
General Build Instructions
Build Order
When putting together the PCB, it’s recommended that you do not yet solder any of the enclosure-mounted
control components (switches) to the board. Instead, follow this build order:
1. Attach the audio jacks, DC jack and footswitch to the enclosure.
2. Remove all nuts and washers from the toggle switches. For each of the switches, thread three nuts
rmly onto the shaft as far down as they’ll go. The additional nuts serve as spacers so that the PCB is
mounted at the correct height.
3. Firmly attach each of the toggle switches to the enclosure, taking care that they are aligned and straight.
4. Push the LED1 into the hole in the enclosure with the leads sticking straight up, ensuring that the at side
is oriented according to the silkscreen on the PCB.
5. Attach the hex stando󰀨 to the enclosure using a screw from the outside. If you have a countersink drill
bit, you can countersink the hole from the outside and use the at-head screw so that it’s level with the
enclosure. Otherwise, use a pan-head screw here.
6. Ensure that the bottom (clock) PCB has the female header sockets soldered in place and that they are
at a straight 90° from the PCB. Fit this PCB onto the toggle switches as well as the hex stando󰀨 and the
leads of the LED. Use a 6-32 x 3/8” panhead screw to attach the PCB to the stando󰀨. The PCB should
rest just slightly above the at base of the toggle switches, but below the top of the lugs. If it doesn’t t, or
if you need to bend things more than you think you should, double-check the alignment of the switches.
7. Once you feel good about everything, solder the toggle switches from the top.2 By soldering them in
place inside the enclosure, there is no stress on the solder joints from slight misalignments that do not
t the drilled holes. You can still take it out easily if the build needs to be debugged, but now the PCB is
“custom-t” to that particular enclosure.
8. Wire everything on the bottom PCB according to the wiring diagram.
9. On the top (signal) PCB, it’s easiest if you do not yet solder the male header pins. Instead, attach the
header pins to the female sockets of the lower PCB. Then, put the top PCB in place, tting the header
pins inside the proper holes, and solder them in place. Once again, this helps “custom t” the pins
together so that there is no stress on the solder joints from slight misalignments.
10. Wire everything on the top PCB according to the wiring diagram on the last page.
1For the LED: You can use a bezel if you’d like, but generally it’s easier just to drill the proper size of hole
and push the LED through so it ts snugly. If you solder it directly to the PCB, it’ll stay put even if the hole is
slightly too big. Make absolutely sure the LED is oriented correctly (the at side matches the silk screen) before
soldering, as it’ll be a pain to x later! After it’s soldered, clip o󰀨 the excess length of the leads from the top.
2Note on soldering the toggle switches: It will require a good amount of solder to ll the pads. Try to be as
quick as possible to avoid melting the lugs, and be prepared to feed a lot of solder as soon as the solder starts
to melt. I recommend waiting 20-30 seconds between soldering each lug to give it time to cool down.
Sockets
Since double-sided boards can be very frustrating to desolder, especially components with more than 2
leads, it is recommended to use sockets for all ICs. It may save you a lot of headaches later on. This PCB is
particularly di󰀩cult since the pad, hole and trace sizes are smaller than most other DIY projects.

17BLUESHIFT CHORUS / BOSS DC-2 DIMENSION C
Checklist
I have tried to be as thorough as possible in this documentation, but the upshot is that by providing so much
information, some of the most important details may be missed. Here are the high-level things to make sure of
before turning it on for the rst time:
• I have chosen a bypass method (page 15) and set the jumpers on the optocoupler accordingly.
• I double-checked the orientation of all of the ICs in their sockets.
• I’m using a stereo jack for Output B.
• I’m using female header sockets that are at least 0.325” (8.25mm) in height from the PCB.
• I triple-checked the wiring against both the diagram and the table on page 15.
• I double-checked the orientation of the LED before soldering it in place.
License / Usage
No direct support is o󰀨ered for these PCBs beyond the provided documentation. It is assumed that you
have at least some experience building pedals before starting one of these. Replacements and refunds will not
be o󰀨ered unless it can be shown that the circuit or documentation are in error. I have in good faith tested all of
these circuits. However, I have not necessarily tested every listed modication or variation. These are o󰀨ered
only as suggestions based on the experience and opinions of others.
Projects may be used for commercial endeavors in any quantity unless specically noted. No bulk
pricing or discounting is o󰀨ered. 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, and (2) you cannot
“goop” the circuit, scratch o󰀨 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 e󰀨ects pedal industry needs more transparency, not less!)