Its just a none powered, zero gain stage, usually for source selection and volume control. basically its a volume pot, switch and in-output connections in a box. Hook it up like a regular preamp source in - amp out.
Passives adds little to the signal ( minimaly a volume so that's the attraction. there is advantages and disadvantages with either passive or active preamps.
Passives adds little to the signal ( minimaly a volume so that's the attraction. there is advantages and disadvantages with either passive or active preamps.