The Sonifex Stereo Line Isolation Unit is used to isolate audio signals from inter-area ground hum loops, which could be caused by equipment being powered by different mains power supplies, or different phases on the same supply. This unit is useful where audio is required to be driven over a relatively long length of cable by isolating the signal using transformers, ground loop currents that can be present in non-isolated signals, are eradicated completely. The input and output are connected through a transformer, which has internal jumpers allowing the outputs to be balanced about ground. In addition, there is a loop-through output, so that the stereo isolation unit can be inserted into a line, forming a transformer balanced distribution point.