The Rosetta, by default, is calibrated for -16 dBFS. To calibrate the Rosetta, press and hold the SoftLimit button until it begins to flash. Send a +4 analog tone into the analog inputs. The metering in calibration mode now reflects -21 dBFS to -11 dBFS. To calibrate to -12 dBFS, turn the A/D calibration trimpots. As the level increases one LED, which equals one dBFS, the over light will turn on indicating you have achieved the next level up in dBFS. Each LED you light up will cause the over light to come on and as you increase the gain the over LED will go off until the next LED is lit up. When you get to the desired level, stop as soon as the over LED lights up.