Mesa/Boogie Mark IV Amplifier - Manual (Page 21)

PAGE 17
Description of Tube Functions
V1A= Input Stage
V1B= Tone Recovery Stage
(post tone controls)
V2A= Third Gain Stage (Rhythm Modes)
and Fifth Lead Gain Stage
V2B= FX Return Stage V3A= First Lead High Gain Stage
V3B= Reverb Return
V4A= Second Lead
High Gain Stage
V4B= Reverb Send
V5= Phase Inverter
Power Tube Substitution:
6V6's in Tweed & Simul-Class
in all 4 sockets.
5881's in all 4 or Class A Sockets.
EL-34's in Class A sockets only.