Okay. so yesterday i finally got my modded guitar tube preamp (an ADA MP-1 from the 80's) . the mod pretty much turned its marshall like twangy quality to a darker and creamier type of distortion close to the Mesa Boogie amps. Now the ada is loaded with 2 12AX7A/7025 tubes. I figure tubes are matched according the the type of amplification/signal shaping the preamp gives. so since i pretty much reversed my preamp's tone, new tubes would be in order.

While looking I've stopped on the 12AX7EH

(http://www.thetubestore.com/ehx12ax7.html)

I'm sure there's at least one crazy audiophile here that could point me to a good Tube resource, right?

Your best option would be talking to Bob from Eurotubes. http://www.eurotubes.com/index.htm

Send him an email and tell him what you're looking for and he'll be able to tell you the right kind of tube. I got one for him with my MP1 with the same mod as yours. If I remember correctly it was an ECC83S but it was a long time ago and I might not be remembering well.

yeah, looked at his site and stopped on the ecc83s too. seems to be what i need. though i'm still searching.