The present invention concerns a converter unit comprising an ultrasonic transmission element having a transmission surface for transmitting an ultrasonic vibration to a tool which can be fixed to the transmission surface or to a material which is in contact therewith in the longitudinal direction along a longitudinal axis of the ultrasonic transmission element, and at least one ultrasonic transducer for generating an ultrasonic vibration with a propagation direction which is not oriented along the longitudinal direction, wherein the converter unit has an ultrasonic natural frequency. To provide a converter unit having an ultrasonic transmission element which has a transmission surface for transmitting an ultrasonic vibration to a tool which can be fixed to the transmission surface or to a material which is in contact therewith in the longitudinal direction along a longitudinal axis of the ultrasonic transmission element and at least one ultrasonic transducer for generating an ultrasonic vibration with a propagation direction which is not oriented along the longitudinal direction, wherein the converter unit has an ultrasonic natural frequency with which a high vibration energy can be generated, it is proposed according to the invention that the ultrasonic transducer is arranged in the propagation direction in a region of ±λ/4 about the longitudinal axis of the ultrasonic transmission element, wherein λ is the wavelength of the vibration belonging to the ultrasonic natural frequency.