General Information About Tube Types - Rivera R100-212A Owner's Manual

Chubster 55, Suprema, R55-112
V6
V1 V2 V3
Location Type
V1 12AX7
V2 12AX7
V3 12AX7
V4 12AX7
V5 12AX7
V6 EL-34
V7 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, V7 Power amp tubes--for best operation, they should always be changed in pairs

General information about tube types

EL-34 is the most common European type of Power Output Tube. There are 4 factories
in the world building this tube; Svetlana in St. Petersburg, Russia, Reflector (Sovtek) in
Russia, JJ/Tesla in Slovenia, and a factory in China. NOS (New old stock) supplies from
various other factories are still available, albeit in short supply. Out of all that are
currently made, we have had the best success with the Svetlana.. The tone of EL-34's
is very different from 6L6GC. We are very critical in our testing of our tubes, and throw
away many that do not make our grade. All of our amps are built with matched tubes,
that are graded as well. When you need to purchase replacement tubes, if you order the
same grade number that are in your amp originally from the factory (provided that no
one has changed the bias set at the factory), you can change out the tubes without
needing the bias to be re-adjusted. If you use tubes not from us or of a different grade
or value, you will need to have the amp rebiased. In terms of 12AX7A types, there are
only 3 factories that we know of building this tube type; JJ/Tesla, Sovtek, and Ruby
Tubes in China. Again, NOS stocks still exist of RCA, G.E., Mullard, Telefunken,
V7
V4 V5
R Series V1.0 p 25