Abstract: A yarn package is frictionally engaged by a roller and driven at a peripheral speed so as to pay off a filament that is wound on a spindle positively connected to the output shaft of a fixed-speed motor. This output shaft is also connected through a steplessly variable transmission to a roller-drive shaft that rotates the payoff roller and therefore determines the linear velocity of the filament. A pair of detectors are provided for generating respective outputs corresponding to the rotation speeds of the motor output shaft and the roller drive shaft. These two outputs are fed to a divider where they are combined into an actual-value signal that is compared with a set point so as to form a difference signal. A regulator operated by this deviation signal acts on the adjustment element of the steplessly variable transmission to maintain a constant ratio between the angular velocity of the two shafts so that uniform twist is imparted to the filament.