Audio isolation transformers are designed to remove hum and buzz created by ground loops. Normal voltage differences in the system grounding points between different pieces of equipment cause small AC power currents to flow in the shield of audio cables. Capacitance between a power transformer’s primary and secondary windings
introduce signals to the circuit ground which will also create small current flows in the cable shield. Either of these problems will create hum in audio signals. A transformer breaks the inter-equipment ground path and greatly increases
the rejection in the input circuits while remaining transparent to the audio signal.
Models are also available with internal video hum eliminator to remove both audio and video interference.