An audio host device has a connector having a speaker contact, a microphone contact, and a reference contact. The reference contact is shared by a microphone and a speaker. The reference contact is also directly coupled to a power return plane of the audio host device. A difference amplifier is provided, having a first cold input, a second cold input, and hot input. The first cold input is coupled to an output of the speaker amplifier, while the second cold input is coupled a sense point for the reference contact. The hot input is coupled to the microphone contact. Other embodiments are also described and claimed.