Marshall sqeally

The only amp I've been able to do this effect with is a Marshall Tube amp (JCM800) - using a wah pedal, turn the amp on about 5 with the gain all the way up in the high gain channel-stand with the pickups as close as you can get them to the output transformer( on the right side looking at the amp) The Wah and proximity to the transformer will give a sqealling/whammy-able type sound....Don't thank me, thank Billy Corgan!