These are preamps with balanced outputs, but as I understand it, they are meant to match up with the different impedances you see out of magnetic and piezo pickups.
They can run on batteries(2x9volts) or a 12v adapter. I have one adapter.
50$ for a unit with ac/dc adapter
40$ for a unit without ac/dc adapter
I know they called it an interface, but it is not for connecting to a computer. These are analog in/analog out.