Impedance plays a factor in audio cables, too. Pro audio cabling is usually designed for low impedance, balanced equipment. The audio cables included in most consumer camcorder accessory packs is for high impedance, unbalanced audio gear.
“Most pros use low impedance audio line, 600 ohm or less, and also use balanced lines,” says Sands. “Balanced line is a three wire system. The signal on a balanced line is carried on two wires. The third is a ground and a shield. Balanced line can literally be run thousands of feet with little loss or noise pickup.”
Regular unbalanced line is simply a shielded conductor; balanced cabling uses two conductors and a shield. Balanced audio equipment uses both conductors in a special arrangement to cancel out noise.
The main difference between the two, aside from their connectors, is that only the latter has the ability to transmit your signal long distances without picking up external noise.
“Unbalanced line only has the two wires for the signal and should rarely be run more than 20 or 30 feet,” says Sands. “I see an awful lot of people. like wedding videographers, running 50 feet or more of unbalanced audio cable and getting noise.”
Depending on who you talk to, BNC stands for Bayonet Nut Connector, Bayonet Naval Connector or British Nut Connector. Whatever it stands for, a BNC connection is the standard for pro video equipment.
It’s that funny looking, twist-on connector that you see on a lot of professional grade video equipment. The BNC connector is found on composite video cables.
“It’s one of the few connectors designed for constant impedance,” says Sands.
This means that unlike other connectors, the BNC connector, as well as the cable, is rated at the right impedance for video.
“It’s also a coaxial connection, so it maintains the shielding all the way through,” adds Sands.
Its design allows the insulation and shielding of the coaxial cable to carry through the connector itself. This prevents breaks in shielding and assures a cleaner signal.
Used in hi-band video systems (Hi8 and S-VHS), these connectors are round, multi-wire connectors. In video, the four wire system carries luminance and chroma signals separately, as well as their associated grounds.