MP-1: What is the purpose of the smaller volume knobs?

[Gotland]

The smaller volume knobs on each side of the main volume -- what do they really do? Anyone knows?
Are they intended for volume balance? Or to moderate high input from a source? Do they extend tube life if turned down? What in the amplifier is affected? Are they in the signal path? Just wondering...

 

[Another Johnson]

Perhaps you’re asking about the gain trim?

The manuals are available on the Atma-Sphere web site.