A drive device includes a speed modulation gearbox having a planetary gear mechanism and a casing, a main drive machine which is connected to an input shaft of the speed modulation gearbox, two auxiliary drives, each connected to the planetary gear mechanism via a drive connection. An output shaft of the speed modulation gearbox can be connected to a working machine. The planetary gear mechanism includes a ring gear, a sun gear, a planet carrier and several planet gears. For each auxiliary drive, an additional drive connection with a constant transmission ratio exists between the auxiliary drives and the input shaft or between the auxiliary drives and a driven shaft of the planetary gear mechanism. The additional drive connections can each be engaged or disengaged by a respective switching clutch, wherein the drive connections from the auxiliary drives to the speed modulation gearbox remain engaged in any case.