An investigation into maximizing the dynamic range of a PC sound card based audiometric test system is presented. Two principle sound paths are characterized: a) the analog line input, and, b) internal waveform conversion from digital formats into analog signals. Each signal path's electrical performance and overall dynamic range is measured using audio harmonic distortion analysis and frequency spectrum analysis tools. Recommendations are made for proper combinations of signal amplitude and mixer attenuation settings to maximize overall system dynamic range. This work could be useful for scientists using PC sound card based systems for psycho-acoustic testing purposes or for those using similar systems attempting to test the full range of human hearing.