This riff is played 4 times. The 1st time through a Mullard ECC83 (both triodes in parallel), 2nd through the old stock Telefunken EF86, and third through BOTH preamp tubes. The fourth riff same as 3rd, but with UR12's VVR circuit turned all the way down. The master volume is dimed all the time. The speaker is an inexpensive 12" Eminence ceramic in an open back cabinet. Mic is SM57 about 12" away. Bridge humbucker.

B+ is 308V at the plate of the power tube.

The power tube is an old stock Valvo EL84. Sorry, dunno what I was thinking. I originally typed "EL34". I wish I had some EL34s.