A cochlear implant hearing aid system is disclosed. The system comprises an external unit configured to receive acoustic sound and process the acoustic sound into a coded audio signal, and an implantable unit configured to receive the coded audio signal. Further, the external unit comprises a power supply unit connected via a first path to a switching unit, wherein the switching unit is connected via a second path to ground and is connected at an output thereof to a first coil. Furthermore, the switching unit is configured to operate as a switching element configured to switch between switching states, wherein the switching states include a first state for applying and a second state for not applying a current to the first coil. The coded audio signal is supplied to the switching unit as a control signal, and the first coil is inductively linked to a second coil arranged in the implantable unit. The system further comprises a measuring unit connected to at least one of the first and second paths and configured to measure a dissipative current occurring in relation to the switching states of the switching unit. Based on the at least one measured dissipative current, a resonance frequency of the inductive link between the first and second coils is adapted.