A sound processor apparatus included in an auditory prosthesis system and comprising: an earhook interface assembly that includes a plurality of contacts comprising a first contact and a second contact and that is configured to interchangeably connect to a microphone assembly and an electro-acoustic stimulation ("EAS") receiver assembly by way of the plurality of contacts; and a control module communicatively coupled to the plurality of contacts and that is configured to selectively operate in an input mode or in an output mode; wherein, while operating in the input mode, the control module uses the plurality of contacts as input ports to receive one or more audio signals detected by the microphone assembly while the microphone assembly is connected to the earhook interface assembly; and wherein, while operating in the output mode, the control module uses the plurality of contacts as output ports to output one or more EAS signals to the EAS receiver assembly while the EAS receiver assembly is connected to the earhook interface assembly, wherein the control module comprises analog front end circuitry, and, while operating in the input mode, the control module uses the first and second contacts as input ports by: connecting a first signal line included within the microphone assembly to the analog front end circuitry; and connecting a second signal line included within the microphone assembly to ground, wherein the control module comprises an EAS driver, and, while operating in the output mode, the control module uses the first and second contacts as output ports by: connecting a first signal line included within the EAS receiver assembly to a first output of the EAS driver; and connecting a second signal line included within the EAS receiver assembly to a second output of the EAS driver, and wherein the EAS driver outputs the one or more EAS signals to the EAS receiver assembly by way of the first and second outputs in accordance with a differential signaling heuristic. an earhook interface assembly that includes a plurality of contacts comprising a first contact and a second contact and that is configured to interchangeably connect to a microphone assembly and an electro-acoustic stimulation ("EAS") receiver assembly by way of the plurality of contacts; and a control module communicatively coupled to the plurality of contacts and that is configured to selectively operate in an input mode or in an output mode; wherein, while operating in the input mode, the control module uses the plurality of contacts as input ports to receive one or more audio signals detected by the microphone assembly while the microphone assembly is connected to the earhook interface assembly; and wherein, while operating in the output mode, the control module uses the plurality of contacts as output ports to output one or more EAS signals to the EAS receiver assembly while the EAS receiver assembly is connected to the earhook interface assembly, wherein the control module comprises analog front end circuitry, and, while operating in the input mode, the control module uses the first and second contacts as input ports by: connecting a first signal line included within the microphone assembly to the analog front end circuitry; and connecting a second signal line included within the microphone assembly to ground, connecting a first signal line included within the microphone assembly to the analog front end circuitry; and connecting a second signal line included within the microphone assembly to ground, wherein the control module comprises an EAS driver, and, while operating in the output mode, the control module uses the first and second contacts as output ports by: connecting a first signal line included within the EAS receiver assembly to a first output of the EAS driver; and connecting a second signal line included within the EAS receiver assembly to a second output of the EAS driver, connecting a first signal line included within the EAS receiver assembly to a first output of the EAS driver; and connecting a second signal line included within the EAS receiver assembly to a second output of the EAS driver, and wherein the EAS driver outputs the one or more EAS signals to the EAS receiver assembly by way of the first and second outputs in accordance with a differential signaling heuristic.