...is there anything I need to do to make sure my audio files are being played without any kind of processing done to the file?...
Since you asked for both Windows and Mac answers, mine is a general Windows answer...
What DAC are you using? If the DAC manufacturer makes an ASIO driver, you should use it, along with an appropriate ASIO plugin with your software player. If no ASIO driver exists from the manufacturer, you can still use the ASIO4ALL driver (free), or the usbaudio.com driver (not free). Both are excellent.
Also select the "No Sounds" scheme in the "Sounds and Multimedia" area of your Control Panel, and give your audio playback software a highest priority setting.