Hum and Buzz in Unbalanced Interconnect Systems

Often sound systems exhibit strange and perplexing behavior such as hum that appears and disappears when power to other equipment, not even part of the audio system, is switched on or off! Traditional methods to eliminate hum often seem more like voo-doo than engineering and, more often than not, are trial and error exercises that end only when someone says "I can live with that". This author has previously written about balanced lines in audio systems, so this paper will be strictly confined to unbalanced systems.