A method for operating of a metal detection system may comprise a balanced coil system with a transmitter coil that is connected to a transmitter unit, which generates transmitter signals having a transmitter frequency that is selected from a group of at least two transmitter frequencies, and with a first and a second receiver coil that provide output signals to a signal input of at least one amplifier unit included in a receiver unit, wherein the output signals compensate each other so that the system is in balance. A system adapted to operate according to an exemplary method is also provided. In an exemplary embodiment, a control unit generates a control signal according to the transmitter frequency of the transmitter unit and that is provided to the control input of at least one controllable impedance unit, which is coupled to the signal input of the at least one amplifier unit, wherein the control signal is adapted to control the impedance value of the at least one controllable impedance unit in such a way that the impedance value is increased or lowered when the transmitter frequency is increased or lowered.