What is it? A high-performance stereo direct box suitable for stage use with laptop computers. Details Designed to convert sound files from a laptop and seamlessly transfer them to a pair of balanced audio outputs to feed a PA or mixing console, the USB-Pro is said to install automatically without the need for a driver, configuring itself for use with all popular operating systems including Mac OSX, Windows XP, Vista and Windows 7. The design includes a built-in headphone amplifier for monitoring plus balanced Lo-Z outputs with switchable isolation. Unlike devices limited by 16-bit/44.1kHz conversion rates, the USB-Pro offers true 24-bit/96kHz performance for greater headroom and improved detail, eliminating the need for additional sound cards or separate converters when transferring files. Connection to the laptop is via USB type-B port with D-A conversion monitored through the built-in headphone amplifier to ensure the signal is being properly downloaded and converted. A Mono-Sum switch may be engaged to check phasing or facilitate signal distribution to two outputs, should this be required. To eliminate the problem of hum or buzz caused by ground loops, the design includes two 'set & forget' side-access switches allowing insertion of isolation transformers into the signal path to block stray DC voltage offsets and augmented by a ground lift switch. And another thing... The USB-Pro uses Radial’s ‘book-end’ design to create protective zones around the switches, connectors and controls together with a no-slip pad on the bottom of the unit to provide both mechanical isolation and electrical insulation.