I don't really like tube screamers, but I bought one cheap, It sounded terrible so I bought a new chip to replace the old "bad" chip. When I opened it up it was a "legendary" JRC4558D. No disputing in matters of taste. But here's some information, mostly recycled from GEO.

I'm not suggesting that vandalizing effects pedals is a good thing. They might be worth somthing someday.