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Synthesizers and Samplers
MODEL D
Authentic Analog Synthesizer with 3 VCOs,
Ladder Filter, LFO and Eurorack Format
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
1. Small insulated trimpot screwdriver
2. Small Phillips screwdriver
3. A flat 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
985-40000-01103 Rev.A
2021-02-03
Confidential, for internal use only. Not to be reproduced.
page 1 of 23
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Summary of Contents for Behringer D A-440
- Page 1 Synthesizers and Samplers MODEL D Authentic Analog Synthesizer with 3 VCOs, Ladder Filter, LFO and Eurorack Format 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.
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Page 2: Calibration Procedure
MODEL D 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. -
Page 3: Preliminary Procedure
Synthesizers and Samplers MODEL D Preliminary Procedure Follow all steps in the order in which they are presented. The diagram below shows the typical connections for this procedure. MOTŌR49 MIDI Keyboard/Controller Laptop or desktop computer running a MIDI Utility to send SysEx messages (for PITCH CV calibration) USB A MIDI OUT... - Page 4 Synthesizers and Samplers MODEL D 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.
- Page 5 Synthesizers and Samplers MODEL D Carefully undo the 8 screws on the top panel as shown. There is no need to undo any other screws. Take care not to pull on these cables 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.
- Page 6 Synthesizers and Samplers MODEL D 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.
- Page 7 Synthesizers and Samplers MODEL D Highest C6 Octave Adjustment Highest A5 Lowest A2 OSC3 Scale Adjustment OSC3 Range Adjustment OSC2 Scale Adjustment OSC2 Range Adjustment OSC1 Scale Adjustment OSC1 Range Adjustment 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.
- Page 8 Synthesizers and Samplers MODEL D Putting the MODEL D into Pitch CV Calibration Mode 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.) Run MIDI OX on your computer, and go to OPTIONS/MIDI DEVICES.
- Page 9 Synthesizers and Samplers MODEL D Select "Pass SysEx" at the bottom of the Options pull down menu. (It might already be ticked, which is fine.) In the VIEW Menu, select SysEx.. page 9 of 23 page 9 of 23...
- Page 10 Synthesizers and Samplers MODEL D 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. page 10 of 23 page 10 of 23...
- Page 11 Synthesizers and Samplers MODEL D The SysEx message will be sent to the MODEL D, and it will then be in its PITCH Calibration mode. If you wanted, you can use the SAVE AS command in the Command Window drop down menu to save the SysEx message as a file on your computer for later use.
- Page 12 Synthesizers and Samplers MODEL D Pitch CV Calibration continued Follow the procedure on the previous page to put the MODEL D into PITCH Calibration mode using SysEx. Make sure that the preliminary procedures shown in section 5.1 have been followed, and the MODEL D front panel controls and switches are set as directed.
- Page 13 Synthesizers and Samplers MODEL D Connect the positive probe of your Voltmeter to TP2. D3 E3 F3 D4 E4 E4 Start High Calibration. Target voltage is 6.500 Vdc D4 Start Zero Calibration. Target voltage is 0.000 Vdc C4 Start Low Calibration. Target voltage is -2.500 Vdc C#4 Exit Calibration Mode F3 Increment, Coarse Press to increment or decrement...
- Page 14 Synthesizers and Samplers MODEL D Zero Calibration Adjustment Press D4 on the external keyboard to set the Zero calibration value. 0.000 VDC. Measure the output voltage. It should read If required, the output voltage can be adjusted to this value by pressing the following keys. The Pitch/CV output adjustment resolution is about 2 mV C3 = decrement coarse D3 = decrement fine...
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Page 15: Oscillator Calibration
Synthesizers and Samplers MODEL D Exiting the PITCH CV Calibration Procedure When you are finished, you must press C#4 to exit the Calibration Mode and return the MODEL D to normal operation. If you want to do the other calibrations for the oscillators and octave range, follow the procedures shown on the next pages. - Page 16 Synthesizers and Samplers MODEL D The diagram below shows the keyboard notes that are used in the calibrations. Only A2 and A5 are used in the Oscillator calibration, and C6 is used in the Octave calibration. Alternatively, notes may be played using a DAW with a MIDI interface connected to the MIDI IN on the MODEL D. C6 Octave Calibration Oscillator Calibration A2 Low Value...
- Page 17 Synthesizers and Samplers MODEL D Repeat steps 5 and 6 above until both notes are correct in the display. This may need to be repeated several times to get right. Turn OFF the OSC1 switch. OSC 2 Scale and Range Calibration On the PCB, locate the OSC2 RANGE and OSC2 SCALE pots.
- Page 18 Synthesizers and Samplers MODEL D On your external keyboard, press and hold the A2 key and adjust the OSC3 SCALE trimpot on the PCB while observing the tuner display. Repeat steps 17 and 18 above until both notes are correct in the display. This may need to be repeated several times to get right.
- Page 19 Synthesizers and Samplers MODEL D Turn OFF the A-440 switch. Make sure the OSC1 switch is left ON for the next calibration. OSC 2 Scale and Range Calibration On the PCB, locate the OSC2 RANGE and OSC2 SCALE pots. As set up in the previous procedure, the A-440 test tone should be off, and the OSC1 switch should be set on. Turn on the OSC2 switch.
- Page 20 Synthesizers and Samplers MODEL D On your external keyboard, press and hold the A5 key. Listen carefully to the combination of OSC1 and OSC3, and adjust the OSC3 RANGE trimpot on the PCB for zero beats between them. On your external keyboard, press and hold the A2 key. Listen carefully to the combination of OSC1 and OSC3, and adjust the OSC3 SCALE trimpot on the PCB for zero beats between them.
- Page 21 Synthesizers and Samplers MODEL D On the PCB, locate the OSC SW pot Highest C6 Octave Adjustment Highest A5 Lowest A2 OSC3 Scale Adjustment OSC3 Range Adjustment OSC2 Scale Adjustment OSC2 Range Adjustment OSC1 Scale Adjustment OSC1 Range Adjustment Turn all the Octave RANGE knobs to the 2' position in the OSCILLATOR BANK section. RANGE page 21 of 23 page 21 of 23...
- Page 22 Synthesizers and Samplers MODEL D Turn on the front panel OSC2 VOLUME switch in the MIXER section. (OSC1 is already on, OSC1 and 2 Volumes are up). OSC1 ON OSC1 Max OSC2 Max OSC2 ON On your external keyboard, press and hold the C6 key. You should hear both OSC1 and OSC2. Adjust the headphone volume or main volume as required.
- Page 23 Technical specifications, appearances and other information are subject to change without notice. All trademarks are the property of their respective owners. Midas, Klark Teknik, Lab Gruppen, Lake, Tannoy, Turbosound, TC Electronic, TC Helicon, Behringer, Bugera, Oberheim, Auratone and Coolaudio are trademarks or registered trademarks of Music Tribe Global OSC1 Range Adjustment Brands Ltd.