That "Quad" cable is used professionally for microphones and some line level audio, where it provides a tighter coupling between conductors, and thus enhances the common mode rejection in a balanced circuit. In unbalanced audio, the main benefit of having the shield connected at only one end is that any interference that is picked up by the shield is shorted to ground on the sending component, and isn't transferred to the receiving one. The quad construction per se is of questionable benefit in an unbalanced circuit. Two conductor shielded cable, especially that with a foil shield and a "drain" wire, which provides 100% shielding is the most commonly used. In this instance, one of the inner conductors is the signal "hot" and the other conductor and the drain wire is "ground". The shield is connected at only one end.

Coaxial cable is actually fine in almost all situations. Obviously, these interconnects should be routed with care, making sure that they do not run parallel with 120VAC power cords for instance.

[This message has been edited by soundhound (edited April 11, 2003).]