A voltage generator for an X-ray machine comprising an X-ray tube with a cathode and an anode is described. The voltage generator comprises a negative voltage multiplier for supplying a polarization voltage to the X-ray tube and a filament transformer which can be connected to the X-ray tube for supplying an energisation voltage to the X-ray tube. The voltage generator is characterized in that the negative voltage multiplier comprises a cavity able to house said filament transformer.