A partially implantable hearing aid is provided, comprising an external audio signal unit to be worn at least in part in a user's ear canal, an implantable unit and external means for transmitting power transcutaneously to the implantable unit via an inductive link, the external audio signal unit comprising audio signal processing means for producing processed audio signals from input audio signals and means for transmitting the processed audio signals via an optical link through an ear drum to an optical receiver of the implantable unit, the implantable unit comprising an actuator for stimulating the user's hearing, a power receiving means and a driver unit for transforming the received audio signals into an input signal to the actuator.