radial engineering proav2 stereo direct box radial engineering proav2 stereo direct box. the radial proav2 is a passive direct box specifically developed with the audio-video integrator in mind. it has full two-channel stereo functionality. to eliminate the need for various adaptor, a "swiss army" array of connections are provided, including 1/4" for instruments, rca and 1/8" connectors for consumer electronics and computers, and a +4db xlr input for professional systems. front panel connectors can also be used as thru-puts to allow multiple patch points. custom wound transformers are employed, which are able to withstand exceptionally hot levels while maintaining linearity from 20hz to 18.5khz. the resulting smooth bessel curve is warm and natural, making the proav2 passive di box particularly adept at handling digital sources that can sound harsh. transformer isolation adds the benefit of eliminating ground loops that cause audio hum and buzz and video hum bars or snow.