USB-Pro™ Using & Applications

The Radial USB-Pro is designed to be plug and play for easy use. The following describes basic set-up procedures and connections. For more details, we invite you to download the user guide by clicking on the icon at left.

Making Connections

Before connecting, make sure all of the audio levels are turned down or system is turned off. This helps prevent clicks and pops from damaging more sensitive equipment when connecting and powering up. Turn on your computer. Once initiated, connect a USB cable from your computer to the USB-Pro. Note that the USB-Pro employs a USB type-B connector (D shape) which is standard for devices that are upstream from the computer (printers, hard drives, sound cards, etc).

Once connected, your computer will automatically recognize the USB-Pro. The generic drivers are compatible with most operating systems including Mac OSX, Windows XP and Windows 7/8/10. The USB-Pro power on LED will illuminate to let you know it is connected. Go to your system settings/control panel and select the Radial USB-Pro in the Audio/Sound settings. Close and save your system preferences, and open the audio playback program of your choice. Select and play an audio file. To check the audio, plug in a set of headphones or ear buds and listen. So set the level control to 7 o'clock (fully-counter-clockwise) and then increase slowly.

Using the headphone output

The USB-Pro is also equipped with a stereo headphone output. This headphone amplifier is controlled by the master output level control, and is designed to be used to check signal before plugging into a PA system. Adjusting the level control on the USB Pro will affect both the XLR and the headphone output. The 3.5mm (1/8") output is designed for both ear buds and standard TRS stereo headphones where tip-left, ring-right and the sleeve is ground.

WARNING: Be careful! The headphone output is set as loud as possible so that it can be monitored in a live concert environment. If you push the level too hard it may distort or cause hearing damage! The USB-Pro is intended for use by professional audio engineers that are aware of the importance of listening at safe levels.

This same audio level control sets the output going to your PA or recording system. Once you have determined that the signal from the computer is OK, reset the level to 7 o'clock. Plug the XLR outputs to your audio system using standard balanced mic cables. Turn on the audio system, bring up the level and then turn up the level on the USB-Pro. To prevent mishap, always test at a low level.

  • 7 o'clock (fully counter-clockwise) - OFF
  • 9 to 10 o'clock - MIC LEVEL (Direct box)
  • 12 o'clock – Instrument Level
  • 5 o'clock (fully clockwise) - LINE LEVEL

Playing with the switches

Other than the volume control, there are four switches on the USB-Pro:

  • Mono Sum – This is used to flatten the stereo signal to mono so that you can test for phase problems or ensure that the full stereo signal is heard on a mono system. It also lets you use the two XLR outputs to feed two separate audio systems simultaneously such as sending an audio file to a PA system and video conferencing system.
  • Ground Lift – This lifts the pin-1 ground on the two XLR outputs to help eliminate hum and buzz caused by ground loops. Computers are particularly troublesome when it comes to noise.
  • Isolation Transformers - There are two hidden set-and-forget switches on the side panel. These are used to insert transformers into the analog signal path to further eliminate noise by isolating the computer from the audio system. One switch isolates the left channel, the other the right. As transformers can limit the bandwidth of the audio signal, they can be bypassed or inserted as required.