Originally Posted by: RazboI've read "about" tubes, the various types, how to make them, and all kinds of stuff. But I still could use some kind of feedback if anyone had some input.

I'd search The Gear Page first. For example I searched it for "setting amp bias jet city", and got this:

http://www.thegearpage.net/board/showthread.php?t=662492

Santana's "signature tone" is the Mesa Boogie Mark 1 with it's "smooth gain". The best qualitative description I've heard is: Marshall drive is harsh on the surface with a warm, thick core. Conversely, Mesa drive is warm on the surface with the harshness in it's core. Anyway, if that's what you are after, why not try a Mesa Boogie?

http://www.mesaboogie.com/Reviews/ToneQuest-LoneStar/ToneQuest-Mark1-LSReview.htm

Possible issues regarding tubes & biasing: Does the amp in question have a fixed or adjustable bias? Do the replacement tubes require different pin wiring on the chasis?

Regarding different pre-amp tubes:
http://music-electronics-forum.com/t8863/

Regarding different power tubes:
http://www.thegearpage.net/board/showthread.php?t=317598

I think the most important thing is to define your goal as precisely as possible, then do experimenting. Hope this helps! Have fun tone chasing.