The invention relates to a partially implantable hearing aid comprising an external audio signal unit (10) to be worn at least in part in a user's ear canal (12), an implantable unit (22, 122) and external means (38) for transmitting power transcutaneously to the implantable unit via an inductive link (36), the external unit comprising audio signal processing means (16) for producing processed audio signals from input audio signals and means (18, 20) for transmitting the processed audio signals via an optical link (44) through the ear drum (46) to an optical receiver (42, 63, 64) of the implantable unit, the implantable unit comprising an actuator (26, 60) for stimulating the user's hearing, a power receiving means (30) and a driver unit (50, 148) for transforming the received audio signals into an input signal to the actuator.
