So... it's fairly clear that his characteristic grindy sound would come out of a cranked valve amp, whether Hiwatt, Marshall or whatever; but when he switched to more hifi-ish gear later (eg Trace Elliots from early 80's on, through to Ashdown Lab Series stuff today ), what did/does he use to get the dirt for his early classic sound?
Personally, I've never found a really convincing way of getting that sound [i]except[/i] via the cranked-up-valve-amp route.
( Oh no, perhaps I shouldn't have said that - let's not have the thread degenerate into a valves-versus-trannies argument... )