These things might be more important than getting a better fox and hound:
*don't bother to connect to the hot lead of a shielded cable. The shielding will work well and will keep your hound from sensing the signal from more than about an inch away
*similarly, the noise rejection characteristics of a twisted pair minimize the signal that the hound can detect if you connect to the two wires of a twisted pair; instead connect to one or both wires of one twisted pair and one or both wires of another twisted pair
*you'll get MUCH better sensing range, with the wand sometimes picking up the signal from several feet away, if you connect one terminal to an electrical ground and the other to the wire you're trying to locate. To do this on site, stick one clip into the ground (GROUND, not neutral) of an extension cord, then pull the cord with you to different measuring locations (yes, the extension cord is plugged into the wall; you don't need power, just ground, so you can do this even before a building's power has been turned on)
*with that last method, if many wires are not connected to anything, they will inductively pick up the signal, so you'll have to carefully listen to the wand. The signal with the most warble AND the least buzz will be the one you want