Adapter cable
Overview
The term "Adapter cable" is used to describe an interconnect cable with different connectors on each end. This type of cable can be used to either connect two pieces of equipment that both have either balanced or unbalanced connections; or to connect balanced equipment to unbalanced equipment.
Basics
There are two basic types of adapter cables:
- Cables that have connectors for balanced connection on both ends or cables that have connectors for unbalanced connections on both ends. These will be referred to as "Balanced or Unbalanced adapter cables."
- Cable that have connectors for balanced connections on one end and unbalanced connections on the other end. These will be referred to as "Balanced to Unbalanced adapter cables."
Balanced or Unbalanced adapter cables
Balanced adapter cables
"Balanced" adapter cables must be constructed with a cable that has a "twisted-pair" of signal conductors. This means simply that there are two signal conductor wires of equal size and insulation that are twisted along the length of the cable. Twisting the conductors together both helps to insure they retain similar and consistent impedance characteristics and helps reduce the pick-up of interference induced on them by electromagnetic fields. Further isolation from interference is usually provided by an over-all "shield" in the form of a tubular conductor through which the twisted-pair runs. The shield is typically connected to some form of ground that is referenced to signal ground.
The connectors must have three conductors to provide connection for the twisted pair and shield. The two most common type of connector used for analog audio interconnection are the 3-pin XLR and 1/4" T.R.S. "phone" plug. The name "phone" refers to the original use of this type of connector in early telephone "switchboards."
Unbalanced adapter cables
"Unbalanced" adapter cables are usually constructed using "coaxial cable" which means simply that there is one central signal conductor surrounded by a tubular "shield" that serves as both the shield and signal return. The connectors must have two conductors to provide connection for the signal conductor and shield. The two most common type of connector used for analog audio interconnects are the "RCA" or "phono" plug and the 1/4" T.S. phone plug.