Rivera R100-212A Owner's Manual page 26

Sylvania, Mazda, and Philips. Usually the Chinese sound the brightest and have the
most gain. Recently the Sovtek 12AX7LP has been made available and it is improved
from it's predecessors, yet has less gain and less high end than the Chinese. RCA, G.E.
Philips, Mullard (NOS) are great tubes, but may need to be selected for microphonics.
We are using mostly Sovtek for the 12AX7A's. We use 12AX7WA or WB for V1-V3, and
12AX7LP/LPS for position V4 and V5. Together this creates a tone and gain balance
similar to running Chinese 12AX7's.
R100-212
V1 V2 V3
Location Type
V1 12AX7
V2 12AX7
V3 12AX7
V4 12AX7
V5 12AX7
V6 EL-34
V7 EL-34
V8 EL-34
V9 EL-34
Here's a brief description of what each tube does:
V1 Input buffer and tone control driver for Channel 2, and also the first preamp stage of
Channel 1
V2 Tone control follower for Channel 2 and an additional gain stage for Channel 1
V3 Final stages for both channels before the mixer stage
V4 Reverb follower and the mixer stage, provides gain to the reverb pan
V5 Phase inverter driver tube for the power amp section
V6-V9 Power amp tubes--for best operation, they should always be changed in a group
of four
V6 V7 V8 V9
V4 V5
R Series V1.0 p 26