It has been stated here that the Dead used Mac amps exclusively in the WOS but that is not my recollection. In fact if you look at the video: "Video by Justin Kreutzmann of my photo shoot for McIntosh Labs featuring Bob Weir singing a song and hangin' at home." on the Smugmug site:
Pechner Productions : Music you'll see some Phase Linear 700s. I also remember seeing a number of Crown DC300s used in the wall. My first amp was a Mac integrated and my second was a DC300 so I was paying attention.