To provide an audio signal processing unit that processes an audio signal to enhance listening.

A mixer 16 has two input terminals branched from an input terminal IN, one input terminal receives an audio signal from an audio source unit 11 as it is, and the other input terminal receives a signal resulting from the audio signal from the audio source unit 11 in a class C amplifier 12 and a filter 14. The class C amplifier 12 generates an n-harmonic signal from the audio source unit 11. The filter 14 eliminates a signal component in an audible band from the n-harmonic signal generated in the class C amplifier 12. The mixer 16 mixes the audio signal from the audio source unit 11 with a filter signal passing through the filter 14. That is, the listening can be enhanced by adding the harmonic signal resulting from eliminating the audible band component from the n-harmonic signal generated in the class C amplifier 12 with the filter 14 to the audio signal from the audio source unit 11.