The Pro Co Sound UBAC Cable is used to take an unbalanced stereo line level from the RCA connections on your hi-fi system and properly convert it to a balanced Lo-Z microphone XLR male output. This is done by the MMT-1 Hi-to-Lo Z matching transformer, which converts the mono unbalanced line level signal down to a clean balanced XLR output, usable by any Lo-Z input on any audio mixing console.
The MMT-1 is a miniature 150 ohm/15K ohm open channel frame audio transformer.