neutral labs ELMYRA v1.4 User manual

ELMYRA v1.4
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 Elmyra
build, in which case I need to tell you that you are a great person.
Important!
DO NOT EMPTY ANY OF THE COMPONENT BAGS NOW! The components are grouped
into the bags so that all of them can be identified without having to
look up resistor ring codes. Rather leave everything inside the bags
and take out what you need while soldering.

Panel
First prepare the panel. Place the 4 LED sockets in the positions
shown below and secure each one with the nut on the back.
Now put in the 6 touchpads. You must use the plastic washers under the
touchpads on the top side! On the bottom side, tighten the nut and do
not use any washers. The nut must be in contact with the metal film
below.
Then solder the 4 pin SMD header to the back of the panel so that the
pins point toward the bottom edge. Your kit either has an angled
header (right) or a flat one (middle), they both work the same way.

The easiest way to solder this header is to first melt just a bit of
solder on one of the 4 pads on the board. Then plug the female Dupont
connector of one of the 4-pin cables into the header. This will make
it easy to hold while soldering without burning your fingers. Now
solder one of the legs to the pad you have applied solder to. Remove
the cable and solder the other legs.
Do not put any of the pots or switches in at this time. Put the panel
aside and continue with the PCB.
PCB Bottom Side
Solder the bottom side components as described below the table. Where
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 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. Double check the polarity! If the IC is flipped, you will
see the infamous magic smoke and likely destroy the IC and potentially
your PSU!
(D are diodes, R are resistors, C are capacitors, U are the
potentiometers as well as the IC and its DIP8 socket, S are switches
and LED are, you might have guessed it, LEDs.)
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 them.
R1, R15
1 MΩ
no

R2, R17
1 kΩ
no
R3, R5, R7,
R9
47 Ω
no
R4, R6, R8,
R18
4.7 kΩ
no
You can substitute R18 for a
lower value if you like the
power LED to be brighter. Or for
a higher value if you like it
dimmer. Do not go below 50 Ω.
R10, R11,
R12
220 kΩ
no
You could experiment with
different resistor values for a
different touchpad response.
Don’t go below 100k or above 1M.
R13, R14,
R16, R19
10 kΩ
no
C1, C2, C3
1000 µF
yes
C4, C5, C6,
C10, C11
1 µF
yes
C7
3.3 nF
no
C8
4.7 µF
yes
C9
10 µF
yes
C12
0.1 µF
yes
J1
8-pin male
header
no
Polarity does not matter for the
header itself, but for the
cables plugged into it later on!
U1
MCP6002
yes
Solder the socket without the IC
first. Plug in the IC later.
MCU
Itsybitsy
M0 Express
yes
Solder according to instructions
below. DO NOT SOLDER DIRECTLY TO
BOARD!

Begin by soldering the resistors, diodes and IC socket. It helps to
solder one pin first and ease it in place. Pay attention to polarity.
Next solder the male header and all capacitors except for the 3 large
ones (C1, C2, C3). Once more, polarity matters, except for C7!
Then place C1, C2 and C3 into their place and solder. I need not
remind you to check the polarity, right?

Next, break and solder the male headers to the ItsyBitsy board on the
bottom (unpopulated) side. DO NOT SOLDER THE ITSYBITSY DIRECTLY TO THE
PCB! Then break the long female 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. Beware: You will lose 1 pin for each cut.
A wire cutter also works. You might want to use a file to remove burrs
and make everything fit nicely. Put the headers onto the PCB and push
in the completed ItsyBitsy board to hold the headers in place.

Solder the female header pins on the other side. After soldering,
unplug the ItsyBitsy board again. It should look like this:
The bottom side is done. You can plug the MCP6002 in its socket now
(check polarity!).
PCB Top Side
Now place all the components on the top side of the PCB according to
the table below. Be sure to put the LEDs all the way in at this time.
Pay attention to LED polarity. DO NOT SOLDER ANYTHING YET OR YOU MAY
NOT BE ABLE TO FIT THE PANEL!
Part
Type
Polarity
matters?
Notes
U2 - U11
10 kΩ
linear pot
yes
S1 - S8
SPDT
switch
no
Unscrew the top nut, remove both
washers for now (keep the
knurled washer and discard the
anti-rotation one if it’s
there), screw in the bottom nut
to about 1 mm before the stop.

LED1 - LED3
orange LED
yes
The short leg towards the PCB
top edge (flat side of the
printed circle).
LED4
blue LED
yes
The short leg towards the PCB
bottom edge (flat side of the
printed circle).
Carefully place the panel on top of the PCB and wiggle it into
position. There are 2 ways to do this: Either force the switches to
remain in the (non-existing) middle position, which can take some
convincing. Or put them all in the down position and slightly tap the
switches one by one with a long object (e.g. a screwdriver), until
they’re all in their mounting holes. Press the panel into place. Once
everything is snug, put washers and nuts (hand-tight is enough for
now) on top of only the U2 and U11 pots and flip everything over.
Push the LEDs all the way into their sockets. Be careful not to bend
their legs.
Solder all the top panel components now. The switch holes may be a bit
larger than needed (to accommodate for several types of switches), but
it’s easy to get the switches aligned if you solder only their middle
pins first, then align, then solder the other 2 pins.
Your PCB top side should look like this after soldering. (You don’t
actually have to remove the panel. It was just done for the picture.)

Now put the ItsyBitsy back in place. It’s not a good idea to put on
and tighten all the nuts now. Better wait until everything else is
complete, in case you need to troubleshoot.
Connect Panel and PCB
You can now connect the panel and PCB with the provided 4 pin Dupont
cable. Use the cable that has Dupont connectors on both sides. The one
that has open wires on one end will be needed later to connect the
input and output jacks.
Check the panel and PCB images below and connect as follows:
●panel pin 4 to PCB pin 5
●panel pin 3 to PCB pin 6
●panel pin 2 to PCB pin 7
●panel pin 1 to PCB pin 8
Power and Audio In/Out
Cut the single wire in 2 and solder it to the jacks as shown below.
This is for the ground (GND) connection between the jacks. When
soldering 2 pieces of wire to a single lug, it can help to make the
solder connections in 2 different places on the lug to avoid the first
wire coming loose when soldering the second one.

Now solder the remaining Dupont cable to the 3 solder lugs as
indicated in the picture below.
Make sure there is no
accidental solder connection
between lugs. Also watch for
loose strands of wire,
especially between the 5V and
GND inputs. A short in this
location might damage your
power supply.
Arrange the wire so that a plug
will not touch or even jam it
when plugged in. It helps to
keep the wires reasonably short
for this reason.