The 888/24 is factory calibrated so that it's operating level is +4 dBu with 18 dB of headroom nominal at full code, unity gain, making calibration unnecessary for most professional applications. However, you may want to calibrate the inputs and outputs of the 888/24 to the operating level of your mixing console, so that the output meters of the 888/24 match the levels of your console. Additionally, you may want to re-calibrate you interface if you feel that the inputs or outputs of your 888/24 are not recording or playing back at equal levels.Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance.