lowering a gainstage in a preamp

[jmasciswannabe]

I have been making many guitar effect pedals and am excited to start using them. Unfortunatly I am an owner of the 5150 head (horrid clean channel) I have read here and there that the clean channel can be "cleaned" up by lowering a gainstage in the preamp. I am assuming this should be as simple as changing a resistor, but I don't really understand the schematics I have read on the 5150 and I have never worked with tubes before. Can anyone offer any suggestions on what to look for?

https://schematicheavencom.secure.powweb.com/newamps/peavey_evh5150.pdf

ps I have posted this on the ampage site as well....