I spent 45 seconds over at the metroamp forum and found something I have read awhile back. Here is the link and a quote from Dave Friedman on the subject:
http://forum.metroamp.com/viewtopic.php?f=16&t=3521
David Friedman
Very simple. Rudy leiren told me personally. Flange phase echoplex into a marshall with variac to 90 into only one cab. The univox echo or whatever was only patched into the chain for eruption he also used a eq for eruption. Eq was also occasionally used for tone shaping with amps that did not sound as good. This was the core setup. As more vol was needed more amps were added and more cabs but sill only one per amp. There really is nothing more to it. Lots of sustain and feedback from the sheer vol of it all. Now ed was always experimenting and still does to this day so there might have been some mishaps along the way like tubes melting etc. No lying just things not explained the right way out of a lack of technical knowledge.
Well here is what i was told by Rudy Leiren his long time tech. This was just last week. His setup was flanger phaser echoplex amp. His main 100 watt was used on everything. The bias was turned all the way up and the variac was set to 91v. into only 1 cab.
There is a pic of the early days with a 50 watt and a vox. He told me the 50 was a back up to the 100 and the vox was a last ditch back up. He often borrowed amps for his back ups. In fact he told me a story that at a party they were playing ed blew a fuse in his main amp and did not have a backup and had to rum home to get a fuse while the band was playing. After this he always made sure he had a backup. Now Rudy said the eq pedal was used only for certain guitars or sometimes when he used rental gear that sounded bad. Also the univox echo was patched in by hand for eruption only and then was taken out of the chain after. Later there was another cab on Mike side that was driven from another amp they used a splitter to do this. As time went on more cabs where used and so where more amps. The amps would only drive one cab though. Now he did say ed was always trying shit but would always come back to this set up. This info follows everything ed has ever said to me personally. Also when 84 hit he changed his set up to H&H power amps and some different effects etc. He still used a cab off the head though no load resister. The Load resister came for the 5150 tour.