The ALI20/25 are Audio Line Isolators, designed to isolate audio devices from each other, in most cases they are used to avoid hum, caused by ground loops in audio systems. They offer a complete passive solution for the isolation of a stereo balanced audio signal. It features dual XLR in- and output connectors and a ground lift switch. The in- and output phase are matching. The ALI20/25 are both built with an audio transformer that has a turns ratio of 1:1 and an impedance of 600 Ohm. The difference is the shielding of the transformer. The ALI20 contains a shielded transformer which complies with the requirements of most standard applications, while the ALI25 contains a MU-metal shielded transformer which can be used when regular shielding becomes inadequate. This ensures the best results in even the highest EMI polluted environments.