M-Audio Fast Track Pro 4x4 Mobile USB Audio/MIDI Interface with Preamps Interface Type: USB, 2 x 1/4-Inch TRS phone (balanced),4 x RCA phono (unbalanced) Analog Outputs, S/PDIF digital I/O with 2-channel PCM System Requirements: Minimum Operating System - Apple Mac OS X 10.3.9, Apple Mac OS X 10.4.2, Microsoft Windows XP SP2 24-bit / 96kHz audio interface with dual mic / instrument preamps 20dB pads for gain staging 1/4-Inch headphone output with level control and A/B source switch