Two balanced XLR analog inputs are located on the back of the A2D2, both using Burr-Brown analog input circuitry. Two input level modes are available: Calibrated and Variable. In Calibrated mode, two recessed, 24-turn pots allow precision adjustments for input levels in fixed installations where immediate adjustment is not necessary. In Variable mode, two additional potentiometers with external knobs are provided for left/right variable-input control — these being much more accessible when the operating engineer needs quick access to the input levels. Both input modes accept incoming signals from -2 dBU to +28 dBU. Factory calibration places 0 dBFs at -18 dBU.