Majella MCVC User manual

MCVC
DIY MANUAL
Version 1.0

MCVC
DIY Manual
©2019 Majella Audio
2
INTRODUCTION
THE MCVC (MIDI to CV Converter)
The MCVC is a four-channel MIDI (Musical
Instrument Digital Interface) to Control
Voltage (CV) converter. The MCVC is a
straightforward interface between the
Eurorack synthesizer system and devices
that communicate using the MIDI -
protocol. The MIDI CV Converter bridges the
gap between MIDI and Eurorack systems,
by converting MIDI messages to control
voltages, corresponding to eurorack signal
standards.
CONTENTS
The MCVC comes in a box and is fully
assembled and tested. Included are a 16-
pin IDC power cable and M3 mounting
screws + rack crash protection washers.
SUPPORT
If you have any further questions or queries
please contact:
[e-mail]
SPECIFICATIONS
Below are the specifications of the MCVC.
!!Dimensions 128,5 x 70,8 (14 HP) x
15mm
!!Doepfer A-100 compatible
!!16pin Power (
Using 5V rail!
)
!!Current usage: +12V 39mA, -12V
.25mA, 5V 30mA.
POWER CONNECTION
This Module is designed to be connected to
a Eurorack system power supply using a 16
pin ribbon cable. The -12V (red lead) should
be directed as shown in the picture below.
WARNING!
The MCVC is designed for Eurorack systems.
The supply should be +-12V and connected
signals should not be outside of the +-12V
range! Do not reverse polarity when
connecting the power, this will damage
your module permanently!
Please treat your Majella Audio products
with care. Majella Audio does not offer
warranty for any damages to the MCVC due
to accidental damages (fluid spills,
scratches, wrong input/output connections
etc.)

MCVC
DIY Manual
©2019 Majella Audio
3
Requirements
The kit contains the PCB with all SMD parts
pre-soldered, panel and all electrical
components to finish the module. You will
need (as a bare minimum): basic soldering
tools and a Digital multimeter to finish this
module.
Required tools:
•!Soldering iron/station 
•!Soldering tin 
•!Wire cutter 
•!Multimeter (minimal 3 decimals)
•!Trim screwdriver (flat)
•!2 mm Allen key (hex key)
•!Nut driver (plier, at own risk)
Bill of materials (BOM)
To start, it is good practice to check if the kit
is complete. We double check the kitbags,
but its never a bad idea to triple check.

MCVC
DIY Manual
©2019 Majella Audio
4
IC socket (1x 8 pin)
Its best to start with the lowest parts on the
top side of the MCVC printed circuit board
(PCB). The yellow marking in figure 1 shows
its placement.
Please note the orientation of the IC
(socket). The notch in shows where Pin 1 of
the socket is placed and should be pointed
upwards as shown in figure 1.
Figure 1: IC Socket placement
(YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
5
Capacitors (12x)
There are 12 capacitors (100nF) that need to
be soldered. The placement is shown in
figure 2 (yellow markings).
Figure 2: 100nF capacitors placement
(YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
6
Trimmer (1x)
Now we solder the trimmer. See figure 3 for
its placement (yellow marking). Mind its
orientation! The small trim screw should be
pointing towards the left as shown in figure
3 (yellow marking).
Figure 3: Trimmer (YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
7
Minijacks (17x) Take care on this one!
We advice to (without soldering) place the
jacks into the PCB (yellow marked, figure 4).
Then place the panel on the jacks. Carefully
turn around the MCVC and lay it down on
supports, as shown below in figure 5:
Figure 5: support
Solder one pin from each connector. Make
sure to press the panel so that each
minijack connector is tight pressed to the
PCB when soldering the pin. Check if all
minijacks fit tight between the panel and
PCB. Then solder the rest of the pins.
Figure 4: 3.5 mm minijacks (YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
8
Switch (1x)
Next up is the switch. It should be placed as
marked yellow in figure 6. Make sure it’s
tight to the PCB. When soldered, toggle the
switch downwards, this will make it easier
to fit the panel on top later on.
Figure 6: Toggle switch (YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
9
Headers (1x 16pin, 1x 6pin)
The 16pin header and the 6pin header
should be placed on the bottom side of the
PCB (the back of the module). This is show
in figure 7 (yellow marking). MIND its
orientation! The Notch is shown in figure 7.
Figure 7: Headers (YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
10
LEDs (4x)
There are 4 LED’s that need to be placed.
The orientation of each LED is very
important!
The anode (+ positive, long leg) is placed to
the left for LED 1 – 3, and placed to the right
for LED 4. This is shown in figure 9. The
anode (+ positive, long leg) is marked with a
red dot in figure 9.
Figure 9: LED orientation (YELLOW)
It helps to use the panel while placing the
LED’s so that they fit the panel nicely.
Figure 8: LED’s (YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
11
MIDI connector (1x)
Now we are going to solder the MIDI
connector as shown in figure 10. Make sure
its straight.
Figure 10: MIDI (DIN) connector
(YELLOW)

MCVC
DIY Manual
©2019 Majella Audio
12
Trimming
Step 1: Use a multimeter and a small flat
screwdriver. Measure at the measurement
point as shown in figure 11. Trim the
potentiometer until a voltage of about
10.6V is set.
Step 2: Connect a Midi keyboard and play A
notes. Measure the output pitch voltage on
channel 1 (See figure 12).
Play note A in different octaves until you
have a note A, which is close to 4V.
Trim it to exactly 4.000V (or as close as you
can get).
Figure 11: 10.6V start point
Figure 12: A4 should be 4V. (Octave can
differ)

MCVC
DIY Manual
©2019 Majella Audio
13
Montage
Now that everything is soldered and the
device is tuned, we can montage the panel.
It is however possible to tune the MCVC
while the panel has been placed.
Place the two spacers/standoffs (yellow
marking on figure 13) and screw the black
3mm screws from the back (PCB). Place the
panel and screw all hex nuts + the 2 silver
3mm screws as show in figure 14.
Figure 14: final montage
Figure 13: standoffs (Yellow)

MCVC
DIY Manual
©2019 Majella Audio
14
Bill of materials (BOM)
Quantity
Value
Device
12
100nF
Capacitors
1
6n137
Optocoupler
1
8 pin
IC socket
4
RED
LED’s
1
DIN
MIDI connector
1
Toggle
Switch
1
6 pin
IDC header
1
16 pin
IDC header
17
Minijacks
Minijack connectors
1
10k
Trimmer
2
Standoff (hex)
montage
2
3mm Screws (Black, hex)
montage
2
3mm Screws (silver, hex)
montage

Special thanks to:
Rob Cottam
MCVC User Manual
version 1.0
23-10-2019
©2019
https://majella-audio.com
[e-mail]
Designed and made in the Netherlands