Glensound GS-ET04 - Quad Channel Audio Transformer IsolationThe Glensound External Transformer (ET) range was designed to help a specific outside broadcast customer who was having no luck in curing hum problems with cheap DI boxes. This customer was providing audio facilities in a venue away from the OB truck and there was sometimes hum being received at the OB truck on his output circuits. The input circuits of a professional audio device should of course be able to handle this situation but as our customer