A control unit for yarn-braking devices in weft feeders for looms, in which the yarn unwinding from the feeder is pressed between a drum and a braking member connected to two linear actuators controlled by position and provided with position sensors. A position control loop receives a position signal from the sensor and compares it with a reference variable in a subtracter for obtaining a position error. A position compensator receives the position error and outputs a reference current entering a current control loop connected to generate a voltage that supplies the actuator. The compensator incorporates a control transfer function that is variable as a function of an elastic constant of a mass-spring equivalent system, where the mass is the mass of the parts in motion between the braking member and the actuators, and the elastic constant matches with the elastic constant of the elastic elements.