The "Phoenix Connectors" (the modules the wires go into), on this product come in the CLOSED or TIGHTENED position. This is not described in the pre-printed instructions. You first need to unscrew the connection THEN insert the wire. Many people have been trying to insert the wire first and tighten an already fully closed screwdown. When in doing so, the screws then strip the Phoenix connector, rendering the connection useless.
Generic Volume Control Instructions Here
An impedance matching volume control will have sets of "jumpers"
to adjust for the overall system impedance. All the volume controls
must have the same settings. Click image for a larger table.