"The Wall of Sound consisted of eighty-nine 300-watt solid state and three 350-watt vacuum tube amplifiers, driving the speakers with a total of 26,400 watts RMS ... Phil Lesh's bass guitar was piped through a quadraphonic encoder that sent a separate signal from each of the four strings to its own channel and set of speakers." This was in '73-74. Rock and roll indeed 8-) Lee