A novel phantom-powered inline preamplifier is configured to provide selective processing of a sound source signal by intelligently determining the need for a low or high impedance matching and transformer coupling, based on high fidelity requirements of a particular sound source signal. For example, the phantom-powered inline preamplifier can intelligently detect a microphone-originating sound source signal and automatically route the microphone-originating sound source signal to a low impedance matching circuit pathway that leads to a phantom-powered output terminal for an optimal hi-fidelity processing specific to the microphone-originating sound source signal. Likewise, the phantom-powered inline preamplifier can intelligently detect a musical instrument-originating sound source signal and automatically route the musical instrument-originating sound source signal to a high impedance matching circuit pathway and optionally couple to an instrument transformer, which leads to the phantom-powered output terminal for an optimal hi-fidelity processing specific to the musical instrument-originating sound source signal.