A device for fragmenting substances comprises a probe having an elongate probe shaft on the distal end of which a probe head is arranged, said probe head comprising an electro-hydraulic converter with which electrical energy, delivered via the probe shaft from the proximal direction, is converted in shock-like manner into mechanical kinetic energy, said converter comprising a housing which accommodates a liquid chamber and a shock-transmitting element which is designed as a piston and which can be moved in the longitudinal direction of the housing from a proximal end position to a distal end position, the distal end position being defined by an abutment on the housing, which abutment is struck by a counter-abutment arranged on the shock-transmitting element. The abutment and the counter-abutment are designed in such a way that, during its movement from the proximal end position to the distal end position, the counter-abutment comes directly into contact with the abutment, and the shock-transmitting element is moved back again to the proximal end position essentially by the impact on the abutment.