Generally 0 dB is the reference value for the mixer, but considering usage in many different environments, this unit's channel level indicator goes up to +4 dB. Furthermore, headroom of +17 dB is provided with internal processing, so the sound is not necessarily distorted even when "OVER" lights. However, this unit is equipped with effects that raise the volume, so we recommend adjusting the TRIM control to a level at which red LED does not light.