Frank, the volume control is a variable resistor which controls the amount of voltage which is let in from the pre-amplifier to be multiplied by the fixed gain factor(again, there are no "gain controls")of the amplifier. If it's set at max it lets essentially all of the voltage through and the overall volume level is controlled by the level controls for the various channels in the pre-amp. So yes, the use of the amplifier volume control is redundant and it should be left wide open.

-----------------------------------

Enjoy the music, not the equipment.