Behringer D A-440 Installation instructions

Synthesizers and Samplers
MODEL D
Authentic Analog Synthesizer with 3 VCOs,
Ladder Filter, LFO and Eurorack Format
985-40000-01103 Rev.A
2021-02-03 page 1 of 23
Condential, for internal use only. Not to be reproduced.
1. Small insulated trimpot screwdriver
2. Small Phillips screwdriver
3. A at sheet of cardboard or other insulator as wide as the MODEL D. (This will help prevent damage to the top panel when it is
inverted and resting on the bottom chassis)
The following equipment is required for the Oscillator adjustment and Octave Range adjustment:
1. An external MIDI keyboard of at least 3 octaves including A2 and C6
2. MIDI cable
3. Pair of headphones or a sound system to monitor the main output
The following equipment is required for the Pitch CV adjustment:
1. Digital DC Voltmeter with a scale that can display accurately to 0.001 V
2. Laptop or desktop computer previously loaded with and running a MIDI utility that can send SysEx commands
to the MODEL D
3. USB type A to USB type B connection cable
User Support Bulletin
Introduction
The unit is carefully calibrated at the factory. The performance may change over time or due to environmental changes,
and the following recalibration procedures will help bring it back to its factory settings. If you do not feel comfortable doing
these calibrations, then we recommend they are done by an experienced audio service technician. This is especially true for
those units that need to be opened to gain access to voltage test points and calibration potentiometers.
CAUTION: Incorrect calibration or damage to the delicate adjustment potentiometers may lead to the unit
becoming inoperable.
Note: Although re-calibration will not invalidate the warranty, any damage caused during re-calibration may invalidate
the warranty.
Equipment required

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MODEL D
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Calibration Procedure
The main printed circuit board (PCB) of the MODEL D has various test points and miniature potentiometers (trimpots) that allow
the various calibration and adjustment procedures to be carried out. This involves lifting up the front panel to allow access to the
bottom side of the PCB.
Three main calibrations can be carried out:
1. The PITCH CV can be calibrated using a computer to send a SysEx command, an external keyboard, and a digital DC voltmeter.
See PITCH CV Calibration.
2. The oscillators can be calibrated using a guitar tuner or the internally-generated A-440 concert pitch, and an external
keyboard. See Oscillator Calibration.
3. The Octave RANGE can be calibrated using an external keyboard. See Octave Range Calibration.
A-440 Reference
The MODEL D A-440 pitch is generated and regulated by the MCU and there is no adjustment required. This set frequency is
used as a reference in the following procedure to calibrate OSC1.
Important Note about Reset
If you have previously adjusted the MIDI IN Transpose or MIDI Note Zero Volts, you MUST reset the MODEL D to its factory
settings before doing the following procedures.
Preparation
Before doing the PITCH CV calibrations, become familiar with, and practice the procedures for sending SysEx
commands to the MODEL D. In this way, you will spend less time with the calibrations.

Synthesizers and Samplers
MODEL D
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Connect the MIDI output of an external keyboard to the MIDI IN connector of the MODEL D.
Connect the external power supply adapter to the rear power input of the MODEL D.
Connect a laptop or desktop computer to the MODEL D USB input. (This is only required if you are doing the
PITCH CV calibration, or doing a Reset.)
Connections
Follow all steps in the order in which they are presented.
The diagram below shows the typical connections for this procedure.
Preliminary Procedure
*Headphones
Power
Adapter
MOTŌR49 MIDI Keyboard/Controller
MIDI OUT
*Active Loudspeaker
*Use Headphones or a Loudspeaker
to listen to the output during
the Oscillator calibration
MIDI IN
Laptop or desktop computer
running a MIDI Utility
to send SysEx messages
(for PITCH CV calibration)
USB B
USB A

Synthesizers and Samplers
MODEL D
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MODEL D Control Settings for Calibration
KNOBS
TUNE 0
GLIDE 0
MOD MIX *
MOD DEPTH 0
LFO RATE 0
SWITCHES
OSC3/FILTER EG *
NOISE/LFO *
SQR/TRNG *
* NO PREFERENCE
KNOBS
OSC1 RANGE 8’
OSC2 RANGE 8’
OSC3 RANGE 8’
OSC1 WAVEFORM SAWTOOTH
OSC2 WAVEFORM SAWTOOTH
OSC3 WAVEFORM SAWTOOTH
OSC2 TUNE 0
OSC3 TUNE 0
SWITCHES
OSCILLATOR MOD OFF
OSC3 CONTROL ON
KNOBS
OSC1 VOLUME 10
OSC2 VOLUME 10
OSC3 VOLUME 10
EXT IN VOLUME 0
NOISE VOLUME 0
OSC1 SELECT ON
OSC2 SELECT OFF
OSC3 SELECT OFF
EXT IN SELECT OFF
NOISE SELECT OFF
SWITCHES
WHITE/PINK *
* NO PREFERENCE
KNOBS
MAIN VOLUME *
PHONES VOLUME *
SWITCHES
MAIN OUT *
A-440 ON
* VOLUME AS NEEDED
KNOBS
CUTOFF FREQ 5
FILTER EMPHASIS 0
AMOUNT CONTOUR 0
FILTER ATTACK 0
FILTER DECAY 0
FILTER SUSTAIN 0
LOUDNESS ATTACK 0
LOUDNESS DECAY SEC
LOUDNESS SUSTAIN 10
SWITCHES
FILTER MODE LO
FLTR MODULATION OFF
KEYBRD CONTROL1 OFF
KEYBRD CONTROL2 OFF
FILTER DECAY OFF
LOUD DECAY OFF
EXTERNAL KEYBOARD
MOD WHEEL DOWN
PITCH WHEEL CENTERED
Turn o the MODEL D power.
Try and do the following steps quickly and carefully to keep any cooling down to a minimum.
Lifting o the top panel
Turn on the MODEL D rear panel power switch and check that its Power LED comes on.
Important: Leave the MODEL D turned on for approximately 30 minutes. This will allow the circuits time to warm up
and the components and performance to stabilise with temperature. Without this warm-up time, the calibrations will
be inaccurate.
Set the MODEL D controls as shown below.
Turn down the MODEL D headphone volume knob, and connect your headphones to the MODEL D headphones
output connector. Alternatively, you can monitor the MODEL D output using the main outputs and a suitable sound
system and speakers.

Synthesizers and Samplers
MODEL D
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Carefully lift the top panel assembly and turn it over so the PCB is facing upwards. Be careful not to pull on the two
cables from the lower side of the main PCB. As your connections to other equipment are still in place, take care not to
pull out any cables or damage them.
Place a piece of cardboard or similar insulator between the controls and the main chassis. This will help prevent
damage to the controls as you lay the top assembly onto the main chassis. To protect the wooden side panels from
being scratched, you can add some protective tape over the top edge of each side panel.
Make sure that the top panel is in a secure position and that it is not liable to be dropped or damaged, or become
disconnected with its internal cables or the MIDI cables or headphone cable.
Double check that the MODEL D controls are still as shown on the previous page, in case they were moved during the
top panel removal.
Because the main PCB is exposed, make sure you are not touching it, and that it is not touching any metal work that
may cause a short-circuit.
Turn on the MODEL D rear panel power switch and check that its Power LED comes on.
Do not turn o the MODEL D or let it cool down, until all the calibrations are completed.
Take care not to
pull on these cables
Carefully undo the 8 screws on the top panel as shown. There is no need to undo any other screws.

Synthesizers and Samplers
MODEL D
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If the A-440 switch is in the ON position, you should hear the tone in your heaphones or main system if you carefully
bring the headphone volume or main volume up.
Now that everything is ready, inspect the bottom surface of the PCB as shown on the next page.
The diagram below shows the Test Points TP1 and TP2 used in the PITCH/CV calibration. Take a look at the PCB and locate these
two test points.
The diagram below shows the adjustment trimpots that are used in the Oscillator and Octave range calibration procedures. Take
a look at your PCB and locate these various trimpots. (The later version of the PCB uses dierent multi-turn trimpots.
DC Voltmeter
DC
Voltmeter
0.001

Synthesizers and Samplers
MODEL D
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OSC3 Scale Adjustment
OSC3 Range Adjustment
Octave Adjustment
OSC1 Scale Adjustment
OSC1 Range Adjustment
OSC2 Range Adjustment
OSC2 Scale Adjustment
Highest A5
Lowest A2
Highest C6
PITCH CV Calibration
The PITCH CV calibration procedure uses a computer MIDI utility to send a SysEx command to the MODEL D to put it into
calibration mode.
Once in calibration mode, a digital DC Voltmeter is used to measure the voltage at a test point while test notes are played using
the external keyboard.
The meter should have a resolution of 3 or more decimal places, for example 0.001 V.

Synthesizers and Samplers
MODEL D
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Run MIDI OX on your computer, and go to OPTIONS/MIDI DEVICES.
Select the MODEL D as the MIDI IN and MIDI OUT.
The following example shows the use of the popular MIDI Utility “MIDI OX” to send a SysEx message from your computer to
the MODEL D to put it into PITCH CV Calibration mode. (This same procedure can be used to send any SysEx message to the
MODEL D.)
Putting the MODEL D into Pitch CV Calibration Mode

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MODEL D
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Select "Pass SysEx" at the bottom of the Options pull down menu. (It might already be ticked, which is ne.)
In the VIEW Menu, select SysEx..

Synthesizers and Samplers
MODEL D
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In the Command Window, enter the SysEx command to be sent to the MODEL D. For PITCH Calibration, the
command is:
F0 00 20 32 00 7F 0E 00 00 00 F7
In the Command Window drop-down menu, select Send SysEx.