Hi pace, it is a D.I. out. You can go straight to the board for live or recorded sound. The preamp has four 9v's. I guess this helps support the power to it, or just requires less power than a Series 1 or 2 that use a power supply. I don't know if the D.I. out is connected in any way to this, but that's what it does. I hope this answered your and other's question.