This thread has the potential for some interesting replies. Good topic. I'll start by guessing that most of Van Halen's stuff came from an old Marshall Plexi head. Don't remember the age of the head. I do know that they were recorded with old bottom cabinets loaded with 25 watt Celestion Greenback speakers. Some sort of Variac was also used as was some kind of graphic EQ pedal along with a script MXR Phase 90 phase shifter pedal. I personally think he hit the amp with the EQ maxed out and up for added gain without the variac but this is only my opinion.
I've heard that a lot of George Lynch's tone on the later albums came from a purple Marshall head belonging to God knows who. I read that he offered to buy it from the owner but was denied.
Guitars/Bass - MIM Fender Classic 50s Strat, MIM Fender Standard Strat, Squier Classic Vibe 50s Tele, Gibson Les Paul Studio, Epi '56 Gold Top Les Paul, Martin DSR acoustic, Sigma Martin Auditorium electric/acoustic, Squier Jazz Bass.
Amps/Cabinets/Modelers - Model 2558 50 watt Marshall Silver Anniversary Jubilee combo w/ Celestion Vintage 30s, 4x12 Marshall cabinet w/25 watt Greenback Celestions, Fender Blues Junior w/ a couple of Billm mods, Line 6 POD 2.0, Roland Micro Cube
Pedals/Effects - Cry Baby Classic Wah, Boss TU-2, Boss NS-2, Boss RC-2 Loop Station, Ross Compressor, MXR Micro Amp, Danelectro FAB Echo, Danelectro FAB Chorus, Danelectro Chicken Salad, Marshall Guv'nor Plus, Marshall Echohead, Duhvoodooman's Zonkin' Yellow Screamer, Digitech Digiverb, Digitech Bad Monkey, Dunlop Fuzz Face, Homemade Loop Bypass pedal, Duhvoodooman's Sonic Tonic (Maxon SD-9 clone +), Voodoo Labs Superfuzz