Proel DB2A Active 2-Channel D.I. BoxD. I. Boxes (Direct Injection Boxes) are part of the essential set of tools required for any professional live sound situation or any application where the audio devices feature diff erent levels, impedance and connections. Transforming audio signals from unbalanced to balanced, D. I. Boxes reduce the possibility of electrical disturbances on the line especially over long cable runs such as from a musical instrument to the FoH mixing console. The DB