Some people say he used a Variac on his marshall others say it was a Phase 90 ??
help?

he used a variac...turns down the voltage of your line voltage...but its really dangerous

variac and phase 90 - variac is so you can run the amp full blast with less volume (those old marshalls didn't have master volume so the only way to get gain was to push em and they are way loud) - like the other guy said - it's dangerous - you can electrocute yourself

For heaven's sake, don't use a variac. That was 1978, long before the advent of the millions of load devices commonly available nowadays. Eddie once said he blew fuses in their practice space routinely and also set his amp on fire with the variac!

Check amptone.com for more.

Basically - He ran into his Marshall into a Dummy load then into a seperate power amp into the 4x12's. He used a variac in the beginning to bring the line voltage down to take harshness off the the line out signal and brown out the sound somewhat. The phase 90 was used after the dummy load just before the power amp.

A plexi is dang important. Check Ebay or plexi palace. Marshall Transistional years of 67-68 were magic. No two were exactly alike, I am told by every amp expert I have talked to. But most 67 plexi's had a similiar magic. Warmth of the jtm45 type circuit, still being a relatively clean amp, excellent output tranys, etc. The variac was cool at the time, but it fried tubes like butter. Boutique amp maker and lover of old Marshalls, Mark Stephenson installs a type of variac that was developed by expert Kevin O'Connor(London Power) that essentially has the same effect but at any volume setting, it is easier on tubes and is completely transparent, so I had installed in my plexi. Works AWESOME!!! Another HUGE factor were 2 other things, vintage greenbacks, and his special wound 335 PAF. Well good news, you can still find this magic pup, so I bought it. It is an all around amazing pup from Seymour Duncan's custom shop 160 USD called the EVH. In 78,Ed approach seymour to replcate his favorite TONE monster pup, you can own it , too. Another, overlooked subtle shimmer to his recorded sound besides the script face phase 90 was the the echoplex. THe tape echos added a type of shimmer to the overall sound. Easily found on Ebay. Better yet, buy a fulltone tube tape echo, even the video demo on fulltone demonstrates that shimmery sound. I don't thik Ed ever mentioned it, he hasn't really mentioned a lot of things, downplaying some things- and it his right I think. However, my ears hear a treble boost of some sort on various VH-1 recordings only. I have a bootleg disc of VH demos and various studio tracks or ed doing takes and that is my feeling. I can also hear board compression on solo sections. Last don't forget the end product, is never the ORIGINAL TONE due to mixing, eq, mastering and most fundamentally distortion added from the recording mics. When I chatted to Brian mena, who has met EVH a couple times at NAMM shows, pre open house hours. He has heard the original amp that EVH professes to and while it sounded great, probably records better; Brian said it sounded nothing like VH-1.
good luck
cary

Many Vintage Marshalls will get you close. A lot of it was just his attack and the way he played and a lot of volume.