From Wikipedia : The improvisational rock band the Grateful Dead employed 48 McIntosh MC-2300 amps as the main power source for their enormous public-address system, the Wall of Sound. Designed by Owsley "Bear" Stanley and others, this system utilized more than 26,000 watts of continuous power fed into JBL and Electrovoice speakers and was renowned for its natural, low-distortion stereo sound which carried for 600 feet without significant degradation.