This is for a friend who is still using one.
There are three switch settings, "0" Low and High
And then two gain knobs without any db information.
I don't know much about the unit, although intuitively I would set the switch to "0"
What should he set the preamp gain knobs for minimal gain, like 10-20db with a Sony M-10?
So far with the Sony at Unity, about 4.5, the knobs seem to work best at about a third of the way up from zero or off.