Fish, Eric means that you should ground the toner's black lead and connect only the red to the speaker wires, even all four conductors.

I once got the strongest signal in some CAT-5 by connecting the black lead to an aluminum ladder, even better than to a true ground.

The high-gain amp (receiver) works best when there is a large difference between the wire you're tracing and earth, as with radio waves.

Connecting both leads results in a small difference between the wires and ground; remember, the receiver is a single-wire device.

Larry
www.fineelectricco.com