In a control device for a technical processing plant, a pneumatically driven actuator having an actuator stem is provided together with a valve operated by the actuator, the valve having a valve stem. A valve element is attached to the valve stem. A stem connector connects the two stems to each other for a forced transmission of axial actuating movements and for modifying an axial distance between adjacent ends of the valve stem and the actuator stem to adjust a total axial length of the two stems. The stem connector comprises two half-shells connected to each other, and two positioning devices are provided for a friction-locking coupling of the half-shells to the respective ends. At least one of the positioning devices is designed to modify an axial attachment position of the half-shells along one of the stems.