Can anyone give me an explanation of gain and drive stages?

[tofisi]

Im verry confused after looking tubes replacement scheme of preamps tube.
-1st,2nd,3rd,4th gain stage?
-1st, 2nd drive stage?

What will happened if I change preamp tube in V3?
Can anyone tell me what this mean?

V1A-- Input Stage
V1B-- 2nd Gain stage CH1/CH3,3rd Gain Stage CH2
V2A-- 2nd Gain Stage CH2
V2B-- n/a
V3A-- 3rd Gain Stage CH1/CH3,4th Gain Stage CH2
V3B-- 4th Gain Stage CH1
V4A-- Reverb Send
V4B-- 2nd Drive stage CH3
V5A-- 1st Drive stage CH3
V5B-- Reverb return
V6A-- 4th Gain stage CH3
V6B-- Effects return stage
V7A&B-- Driver/Phase inverter

 

[eudaimonia02912]

Think of V3 as having a small effect on the texture, gain, and sound of channel 3, and an even smaller effect on channel 2. Throwing a higher gain tube in there will add a little gain to channel 3. Throwing a dull tube in there will smooth out channel 3. Etc.

Changing the V1 tube will have the most dramatic effect on the entire amp, while changing V2 will have a significant effect on channel 2.