Diode Clippers in Tube Amps

Dude, don't mess with those diodes till you learn inside and out how tube amps work. I think you're asking for real trouble.

I wouldnt be the one messing with them, obviously! I'm not very good with a soldering iron cos' my hand aint very steady. Its my dad whod be doing the mods, hes an electronix pro. I built a 20 watt valve amp once. But then, unfortunately i didnt play guitar, so i had no use for it.

OK, if you and he feel confident that you know what you're doing. But I will note that lots of electronics pros have little or no training in valve electronics, since the 1960s when they were widely regarded as obsolete. It's something you have to self-educate on these days, older electronics textbooks being the best resources. And lots of folks build amps from kits or schematics without understanding the theory behind them.

I'd get on Google and read every page you can find on modding the Marshall amp you're looking at. A good place to start is Steve Ahola's site: http://blueguitar.org/ He's also a great guy to ask for helpful advice!
:D

Here's Steve's schematic with suggested JCM900 mods:

According to him, you're OK to simply take out the diodes, or lift one end. :D

Hey, thanks! Thats an amazing site!

All that is sooo much great stuff! But i'd still like to know what marshalls also feature clipping diodes for a special "edge" to the sound/to create the overdrive? Ive heard that Slash's signature 2555 has them.

On Steve's site there's a link to a site named "Marshall Heaven." Might find some schematics over there. Or look on: http://schematicheaven.com/