Although this is not technically a 'guitar' tube amp, it is a tube amp that I use for guitar all of the time... and NOTHING sounds as nice as this thing does for clean tones. (I use it as my 'front end' when going into my DAW for my software amp modelers)
It's an MI-11241 mic pre with a mod to patch directly into the grid.
It has a uniquely built (one of a kind, really) output transformer and uses a 12AY7 as a SINGLE triode.
We've been using these in recording studios for years but you can't find them on the open market. They originally came inside of the old 1950's RCA BC2B broadcast consoles and you had to buy a console to get one... then build a power supply and rack housing to use them.
I bought two consoles from Mark Linett just before he did the Beach Boys albums a few years ago.
But seriously, for guitar clean tones, this is as smooth as silk and has a gentle rise that goes all the way up past 30k.
If you want an impules, I can probably make one, but I don't have an AXE FX yet, so no patches from me for now. (I think/hope I'm on the waiting list for a AXE FX II coupon).
I'll share when it's done...
Or if you want to sample one of my units, Cliff, just contact me.
Here is a copy of the schematics:
RCA BC2B Schematics
All the best to you!
Larry