Here are a few pages re: tube amps that might help you.

• Tube for Dummies – tube terms simplified.
• Bassman 6G6-B Bass channel sweetener – mod for your bass channel
• Carvin Vintage 33 mod – make it more “vintage”.

Also check out AX84.com, a great place for learning how to build amps. AMPAGE.org, is another great place and one of the first on the scene as well as being one of the largest sites! The Aiken Amps Technical pages are a must read for any tube amp owner.