The Radial USB-Pro is a 24-bit digital-to-analog audio converter and direct box that is designed to transfer digital audio files to a balanced mic-level signal suitable for a PA system, recorder, or broadcast feed. One merely connects a laptop computer to the USB-Pro using a standard USB type-B cable. The USB-Pro derives its power from the USB connection and will automatically configure itself to most computers without the need for special drivers to be loaded. Audio may be tested using the front panel earphone outlet and adjusting the level to suit. A mono switch can be activated to test for phase issues or to send the output to two separate audio systems. Side access switches enable the user to introduce isolation transformers to eliminate hum and buzz caused by ground loops. This is supplemented with a ground lift switch that lifts pin-1 on the two XLRs. The USB-Pro can be used for audio playback, system testing and for transferring digital audio files to analog for processing.