A road construction machine, particularly a road finisher or a feeder for a road finisher, with a primary drive unit including at least one combustion engine driving a three-phase generator, and further including at least one connection means for at least one conventional alternating current standard consumer, at least one stabilized voltage supply unit is connected between the connection means and the three-phase generator, wherein the voltage supply unit provides standard mains voltage with a permanently stable frequency at the connection means independent of the speed of the combustion engine driving the three-phase generator.