– Power off the eurorack case and unscrew the uDCO/DCO from the case
– If you just updated the firmware, make sure the USB cable is disconnected
– Disconnect all patch cables from your uDCO/DCO
– Connect the PULSE output to either headphones or speakers so you can monitor tones during the process
– Set all the sliders to their max/upper position
– Connect your MIDI to CV source to the VOCT input
– Locate the CAL switch on the lowest PCB
– Hold down the CAL switch, power up your Eurorack case, wait 3 seconds and release the CAL switch

– Put down your uDCO/DCO back in the case temporarily (not screwed in), do not touch it anymore
– Now you can play all the C notes that you have available in the range of your MIDI to CV interface, but leave enough time between the C notes, so that the tone sequence (see below) has time to finish
– Order doesn’t matter. Just make sure you only send the C notes (for example 1V, 2V, 3V, …) uDCO/DCO input range is -3V to 7V but you only need to cover the octaves that are available to you from your specific MIDI to CV interface.

– After each new pitch CV is received by the module, the uDCO/DCO will play a tone. This will help you know which voltages you sent to the module.
The pitch will be high (1500hz) for positive voltage (0 to 7V) and low (400hz):

-3V -> 3 pulses at 400hz
-2V -> 2 pulses at 400hz
-1V -> 1 pulse at 400hz
0V -> No pulses!
1V -> 1 pulse at 1500hz
2V -> 2 pulses at 1500hz
3V -> 3 pulses at 1500hz
4V -> 4 pulses at 1500hz
5V -> 5 pulses at 1500hz
6V -> 6 pulses at 1500hz
6V -> 7 pulses at 1500hz

– If you accidentally send C2# or D2 instead of C2 (for example), first send C1 or C3 and and then send C2 again, this will overwrite the mistake made before

– When you are done covering all the C’s your MIDI to CV interface can generate, simply press the CAL switch again. The uDCO/DCO will then start its normal operation mode and you can start checking the different octaves

IMPORTANT TO REMEMBER when checking the tuning/calibration:
– The uDCO/DCO will only be in tuning BETWEEN and INCLUDING the C notes you have just sent. If you sent C5 as the highest C note, trying to set the DCO to G5 will not use the calibration data we just gathered. It could be out of tune. Also please remember you can also reach the extremeties of the DCO frequency range (20hz … 14080hz)

– When calibration is done, keep the FM attenuator down if you want to check the uDCO/DCO tuning, noise on the FM input might be added to the pitch data and offset the DCO frequency

– Try to tune the uDCO/DCO to A440hz using the middle A of your MIDI to CV interface, with the coarse “around” the middle position and use the FINE pot to get exactly 440hz

– Software tuners usually can only cover “guitar” frequency ranges, they won’t be reliable for the highest range of the uDCO/DCO (above around 3khz)

– DCOs can have excellent pitch tracking and stability but this doesn’t play very well with VOCT CV inputs, there could be noise in the eurorack system or a bad cable or a uncalibrated MIDI to CV interface. Those disturbances could cause your uDCO/DCO to drift over the octaves. Even though the recalibration of the module in your specific system should fix that problem, if you need 100% super accurate pitch, use the MIDI input and switch to MIDI only mode using the switch at the back of the module.