Actually, the amps are high sensitivity, not high gain.
The gain is limited by the power supply voltage which doesn't really change no matter which amp....
All the power supplies are under 500 volt...
The term "high gain" is a misnomer.
So let's start by understanding what this really is.
"High gain" amplification has it's origins in tube phonograph amplifiers.
The design was copied and applied to guitar amps.
The first high gain guitar amp was envisioned by Marshall / Dudley Craven.
The design was adapted from the fender bassman....which was boosted up beyond the original.
Later (much later) the same design was copied by Mesa Boogie.
They claimed they invented "high gain," but that is an outright lie.
Yes that can be proven from the schematics !
The design of mesa boogie is just another copy of a marshall and a fender basman....same circuit, same tone stack, same power amp and on and on.