A sonotrode (18) for producing a welded and/or soldered join between a cable (17) and a sheath (17), covering the cable (17), comprising at least one working surface (2). The working surface (2) is curved in a concave manner, at least in sections. An anvil (10) comprises at least one counter surface (11) which is curved in a concave manner, at least in sections. The device for producing the join between a cable (17) and a sheath (17), covering the cable (17), comprises a sonotrode (18) joined to an ultrasound source (8) at least at a joining surface (5), and comprising an anvil (10) arranged opposite the working surface (2) of the sonotrode (18). A method for producing a join between a cable (17) and a sheath (17) covering the cable (17) is also disclosed.