A parametric equalizer includes an equalizer circuit, a first protection circuit, a second protection circuit, and a first addition circuit. The equalizer circuit is arranged to receive an input signal, and process the input signal to generate an output signal. The first protection circuit is arranged to generate a first protection signal according to the output signal, the input signal, and a first processed signal. The second protection circuit is arranged to generate a second protection signal according to the input signal and a second processed signal. The first addition circuit is coupled to the first protection circuit and the second protection circuit, and is arranged to combine the first protection signal and the second protection signal to generate an equalizer output signal.