If I remember right, 2 channels with PP ON, using 2 condenser mics (CAD model, 8ma each), all VU meters lit up, the power consumption was 3Watts @ 12VDC.... so that's 250mA.
From there, it goes down to 1.5W if PP is OFF and VU meters are also OFF.
So at 9Volts, doing the math will be 3w/9V = 333mA (or 166mA if PP is OFF and VU meters off)
Will try to get actual readings for 9V one of these days.