The RB-UL4 is a 1U rack-mount quad stereo unit for interfacing domestic, or semi-pro unbalanced equipment to professional balanced line levels. The eight RCA unbalanced inputs have an impedance of 10k Ohms and are routed to four balanced XLR-3 outputs with an output impedance of <50 Ohms. The output gain can be individually adjusted for left and right channels by using pre-set potentiometers accessible through the rear panel.