Serie PowerPro/
PowerPro series
Manual del usuario /
User's manual
15
APPENDIX B. Line connections : unbalanced and balanced
There are two basic ways to transport an audio signal:
Unbalanced line: Utilising a two-conductor cable, it transports the signal as the voltage between them. Electro-
magnetic interference can get added to the signal as undesired noise. Connectors that carry unbalanced signals have two pins,
such as RCA (
Phono
) and 1/4” (6.35 mm, often referred to as
jack
) mono. 3-pin connector such as XLR (
Cannon
) may also
carry unbalanced signals if one of the pins is unused.
Balanced line: Utilising a three-conductor cable, one of them acts as a shield against electro-magnetic noise and is
the ground conductor. The other two have the same voltage with respect to the ground conductor but with opposite signs. The
noise that cannot be rejected by the shield affects both signal conductors in the same way. At the device’s input the two
signals get summed with opposite sign, so that noise is cancelled out while the programme signal doubles in level. Most
professional audio devices use balanced inputs and outputs. Connectors that can carry balanced signal have three pins, such
as XLR (
Cannon
) and 1/4” (6.35 mm) stereo.
The graphs that follow show the recommended connection with different types of connectors to balanced processor or
amplifier inputs. The connectors on the left-hand side come from a signal source, and the ones on the right hand side go to the
inputs of the processor or amplifier. Note that on the unbalanced connectors on the left-hand side, two terminals are joined
inside the connector. If hum occurs with balanced to balanced connections, try disconnecting the sleeve (ground) on the input
connector. Note that the illustrations show what should be connected to what, but that pin locations on an actual XLR
connector are different. Also, pin 2 hot is assumed on XLR connectors.
