EI19 170V Horizontal Audio Transformer Low Frequency Audio Isolation Transformer Product Overview EI19 170V Horizontal Low Frequency Audio Isolation Transformer. This horizontal mount EI19 audio transformer is built for audio signal isolation and impedance matching at 170V rating. It breaks ground loop hum, protects audio circuits and maintains clean sound quality for speaker modules, audio amplifiers, intercom systems and consumer audio devices. It is a drop-in replacement