neutral labs ELMYRA v1.1 User manual

ELMYRA v1.1
by neutral labs

Build Guide
Congratulations on your decision to build the mighty Elmyra. Your life
will change forever due to this experience. If nothing else, you’ll be
in possession of this wonderful machine that you likely did not
possess before. Unless, of course, this is not your first build, in
which case I need to tell you that you are a great person.
First of all, let’s take stock of all the components that go on the
PCB (and 2 that go on the panel).
D are diodes, R are resistors, C are capacitors, U is the integrated
circuit and its DIP8 socket.

Bill of Materials - PCB
Part
Type
Polarity
matters?
Notes
D1, D2
BAT85
yes
Distortion diodes. Can be
substituted by BAT54. You may
try other Schottky diodes as
well, but regular diodes such as
1N4001 won’t have the same edge
to it.
R1, R15
1 MΩ
no
R2, R17
1 kΩ
no
R3, R5, R7,
R9
47 Ω
no
R4, R6, R8,
Rx
4.7 kΩ
no
Rx doesn’t go on the PCB, but on
the panel (see below). You can
substitute it for a lower value
if you like the LED to be
brighter. Do not go below 50 Ω.
R10, R11, R12
220 kΩ
no
You could experiment with
different resistor values in
case you’re using different
types of touch plates. Don’t go
below 100k or above 1M though.
R13, R14, R16
10 kΩ
no
C1, C2, C3
1000 µF
yes
C4, C5, C6
1 µF
yes
C7
3.3 nF
no
C8
4.7 µF
yes
C9
10 µF
yes

C10 (2)
1 µF
yes
There are two C10 on the PCB by
mistake. One should have been
C11, but it’s all good, they
should both be 1 µF. ;)
Cx
0.1 µF
yes
Cx doesn’t go on the PCB, but on
the panel (see below).
JP1
header
no
JP2
header
no
U1
MCP6002
yes
Solder the socket without IC
first.
MCU
Itsybitsy
M0 Express
Solder female headers to the
board. Solder male headers to
the MCU and place it onto the
board.
4-pin header
header
no
This is unused, but you can put
a header there and go from the
USB power into the USB plug on
the microcontroller via this
header if you like. Pins 1+2 are
connected, as are pins 3+4. It’s
not needed though.
black lines
(5)
no
These are jumpers. Use short
lengths of wire across the PCB.
If polarity matters, it means you need to pay attention which way you
solder the components to the PCB or panel. Diodes have a black line on
them which needs to match the black line on the PCB. Electrolytic
capacitors have a short leg that goes on the minus (“-”) side, and
they’re also marked with a printed stripe on this side. The IC has a
dot that must match the notch in the socket. And this in turn should
match the gap on the PCB.
Populate the PCB

Begin by soldering the jumpers, resistors and diodes. For diodes,
polarity matters!
Now solder the IC socket. It helps to solder one pin first and then
ease it in place. Pay attention to polarity. Do not place the IC in
the socket while soldering! Most ICs are severely allergic to heat.
Next solder all capacitors except for the 3 large ones (C1, C2, C3).
Once more, polarity matters, except for C7!
Now solder the headers onto the PCB. Break the long header strip apart
as needed by making a small cut on both sides with a sharp knife and
then snap it along the edge of your workbench. You might use a file to
remove burrs and make everything fit nicely.
Then place C1, C2 and C3 into their place and solder. I need not
remind you to check the polarity, right?
Place the microcontroller into the headers and the IC in its socket.
Do not use excessive pressure. If it won’t go in smoothly, check the

alignment again. Pay attention to IC polarity! Also, you may need to
bend the IC’s legs the tiniest bit to make it fit.
Next step: panel
Now to place all components in their respective holes on the panel.
You’ll need:
Bill of Materials - Panel
Part
Type
Notes
TIME, MIX,
FEEBACK, MOD,
TUNE (x3)
10 kΩ B
You may use higher values, like 22 kΩ
or 25 kΩ, but not higher than that.
Lower than 10 kΩ is not recommended. B
means linear.
FILTER, VOLUME,
SCRATCH
10 kΩ B
You must use this exact value, although
you could use A (logarithmic) if you
prefer a different response curve.
Power LED
3 mm blue
LED
The hole for the socket is 6 mm.
Env LED (x3)
3 mm orange
LED
The holes for the sockets are 6 mm.
Power switch
SPDT
The hole is 6 mm.
ENV switches
(x3)
SPST
The holes are 6 mm. You may use SPDT as
well.
SHAPE switches
(x3)
SPST
The holes are 6 mm. You may use SPDT as
well.
BITE switch
SPST
The hole is 6 mm. You may use SPDT as
well.
Touch pads (x6)
The holes are 5 mm. Make sure to use
plastic washers at least on the front
side, so that the pads do not come into
contact with the gold plating!

Populate the panel
Now place all components in their respective holes.
See this diagram (view from the back of the panel):

Connect wires as shown. First solder the blue and red strands of wire
to their pins. You don’t need to run individual wires, just use a
single one for each colour per row and remove the insulation right
where the solder points are.
For the shape and env switches, if you use SPST, make it so that
they’re closed in the up position. If you use SPDT, the same, but
leave the third pin unattached to any wires. (For SPDT, the middle pin
will connect to either top or bottom pin depending on the position.
Use a multimeter to check if you’re unsure.)
The bite switch gets two individual wires to the PCB. They should be
connected if the switch is in the down position. If you use an SPDT
here, leave one pin empty.
The power switch must be an SPDT. Its middle pin connects to the power
(Vcc) on the microcontroller’s USB socket. You can use a short length
of micro-USB cable or make your own:

The wires inside USB cables will generally be colour-coded. You only
need to use the red and black ones as indicated above, but if you’re
experieced, you may want to connect the others as well, so you’ll be
able to update the ItsyBitsy without having to open your case.
The other pins on the power switch connect to ground (off position) or
5V from your USB input (on position). Then solder the supply side of
the wire to the on position pin and the other side to the middle pin
of the power switch as indicated in the diagram above.
The middle pin also connects to the longer leg of the blue power LED
via a 4.7 kΩ resistor (Rx) right behind the panel. Solder it nicely
and keep the legs somewhat short to keep it from moving. (The high
resistance is used to keep the LED dim, just like the orange ones for
the envelopes. A blue LED connected through a more standard 50 Ω
resistor is blinding! Of course you can change it if you want, but
don’t go below 50 Ω).
The pots for time, feedback, mix, mod, and 3x tune are all 10 kΩ
linear (although 22 kΩ will work as well) and they connect to 3.3V
from the PCB (as seen in the diagram) on the right pin and to ground
on the left pin. (All pot legs referred to are as viewed from the
panel side, so left means the left one when looking at the printed
side of the panel, not at the wiring.) The middle pins all get their
individual wire to the headers on the PCB as indicated by the numbers.

The 3 envelope LEDs all connect to ground on the shorter leg and get
their individual wire to the PCB on the longer leg. The resistors for
the LEDs are on the PCB, so no need to solder any to the panel as you
did for the power switch.
For the volume pot you can use 10k linear, although logarithmic is
fine too. Left leg to ground, right leg connected to the middle leg of
the filter pot, middle leg to audio out jack (via PCB if you like,
there is an in and an out available on one of the headers, otherwise
you can of course go directly to the jack). The filter pot is also 10k
linear, but you could use a logarithmic. Solder the 0.1 µF (same as
100 nF) capacitor (Cx) between the leftmost leg and ground, rightmost
leg connected to audio out from the PCB. Be sure to solder the short
leg of the capacitor to ground if it’s an electrolytic, not the long
one!
The scratch pot is 10 kΩ linear. Solder the rightmost leg to the
middle leg with a short length of wire. Solder a cable there and
another one to the leftmost leg (not to ground!). These go to the PCB
as seen in the diagram above.
The top touch pads are all connected among each other and also to 3.3V
from the PCB. The bottom pads have individual wires to the PCB as seen
in the diagram.
For the touch pads, make sure to use the washers on front and back of
the panel, but front is really important as they must not get into
contact with the gold plating. Wind a bit of wire (once only) for each
pad around the threaded part on the back of the pad, so you pinch it
between the nut and the washer when tightening the nut. Use these to
connect to other pads (top) and also to the respective header pins on
the PCB.
You can collect all wires from the front plate with zip ties and
solder or crimp them to connectors that plug into the headers on the
PCB.

Connect panel and PCB
Now connect the wires from the panel to the header plugs as shown
below. (e.g. JP1/05 goes to the MIX pot and JP2/07 goes to your audio
out jack).
For header JP1:
●01 ENV LED 1
●02 SHAPE 2
●03 ENV LED 2
●04 ENV LED 3
●05 MIX
●06 SHAPE 1
●07 TUNE 3
●08 TUNE 2
●09 FEEDBACK
●10 TIME
●11 GROUND (to panel)
●12 SHAPE 3
●13 ENV 3
●14 ENV 2
●15 ENV 1
●16 unused
For header JP2:
●01 TUNE 1
●02 MOD
●03 TOUCH 1
●04 TOUCH 2
●05 TOUCH 3
●06 ground (to jack)
●07 audio out (to jack)
●08 audio in (from volume
pot on panel)
●09 unused
●10 from BITE switch
●11 to BITE switch and
SCRATCH pot left leg
●12 from BITE pot
middle/right leg
●13 unused
●14 3.3V
●15 unused
●16 to FILTER on panel
Now connect the PCB to the panel. Pay attention to the orientation of
JP1 and JP2. JP1 pin 1 is on the left when seen from above and JP2 pin
1 is on the right!
Power in