A Brief Explanation on Calibration

Our instruments with VCOs (Prophet 5/10, Prophet 6, OB-6, Trigon 6, Take 5, Pro 3) have an internal temperature sensor that is used to write calibration table data for the oscillators and filters across a range of the instrument's operating temperature.

When the calibration is run, the temperature at the sensor is checked, and the resultant calibration data is stored in a table. Whenever the instrument returns to or is at this temperature, the specific calibration table which was written is referenced for tuning purposes. It's also worth noting that the VCO synths have a number of calibration tables that are present per Celsius degree across a range of the instrument’s operating temperature.

As such, if the instrument has not been calibrated across its full range of operating temperatures, it can fall out of tune when it is operating at certain temperatures. You may run the calibration whenever you notice it’s out of tune. However, it shall not be over-calibrated. When the calibration is run at temperatures that are too close to each other, it can potentially create a conflict with the data, which is not helpful for tuning issues.

The oscillators on the Rev2 (also Evolver, Prophet 08, Mopho, and Tetra) are DCOs. Unlike our instruments with VCOs, where there is a table to store calibration data at different temperatures, there is only one calibration data "slot" in the DCO synths. Every time a calibration is run, it overwrites the previous calibration data. Therefore, the calibration shall be run only once after it’s been powered on for 15-20 minutes because that would be the state that the instrument is in most often.

In most cases with the DCO synths, the factory calibration is the only calibration the instrument will ever need in its lifetime. However, if it ever exhibits issues with the voices, you can try running the calibration once at its operating temperature to see if that fixes it.