I'll have to think on that or find some info... it's been a number of years since I've run one. But if I remember correctly, I do not think that the big knob on the 192 adds any gain. I might be wrong, but that is what I'm thinking. Wide open = zero gain... anything else is attenuation.
But the little "screw driver" pots might add gain. I'll see if/what info I might have regarding that. The "screw driver" pots are also used for calibration.
Do you have a user's manual?
I carried two of those beasts around in my gear bag for a period of time.. crazy.
Love that box.... it can soak up a super hot signal!