Randall RB 125

[Muggle]

I just bought this really old rb 125, and I have a few questions. I can't find a manual for it, and the letters around the power switch are mostly worn away, the middle position is off, then there is an up and down position. At first I thought they said AC and DC, but they both look like they both used to say "ON"...anyone have an idea of what they could be?

There is no master volume knob, the gain knob changes the volume. I thought gain was a type of distortion like effect, why does it control the volume?

Also, there is a bass/mid/treble EQ and a 6KHz/1.6KHz/390Hz/140Hz/40Hz EQ, along with a bass/mid/treble EQ on my bass(active PUs). Now, I'm a complete novice and I have no idea how I should position these all. Should I leave them all at the middle position?

Thanks in advance!

[Steveaux]

The Power Switch positions are ...

ON
OFF
ON

The Up position is a Ground Lift.