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Balanced audio
Balanced audio is a method of interconnecting audio equipment using balanced interfaces. This type of connection is very important in sound recording and production because it allows the use of long cables while reducing susceptibility to external noise caused by electromagnetic interference. The balanced interface guarantees that induced noise appears as common-mode voltages at the receiver which can be rejected by a differential device.
Balanced connections typically use shielded twisted-pair cable and three-conductor connectors. The connectors are usually three-pin XLR or 1⁄4 inch (6.35 mm) TRS phone connectors. When used in this manner, each cable carries one channel, therefore stereo audio (for example) would require two of them.
A common misconception is that balanced audio requires the signal source to deliver equal waveforms of opposite polarity to the two signal conductors of the balanced line. However, many balanced devices actively drive only one side of the line, but do so at an impedance that is equal to the impedance of the non-driven side of the line. This impedance balance permits the balanced line receiver (input stage of the next device) to reject common-mode signals introduced to the two conductors by electromagnetic coupling.
Many microphones operate at low voltage levels and some with high output impedance (hi-Z), which makes long microphone cables especially susceptible to electromagnetic interference. Microphone interconnections are therefore a common application for a balanced interconnection, which allows the receiver to reject most of this induced noise. If the power amplifiers of a public address system are located at any distance from the mixing console, it is also normal to use balanced lines for the signal paths from the mixer to these amplifiers. Many other components, such as graphic equalizers and effects units, have balanced inputs and outputs to allow this. In recording and for short cable runs in general, a compromise is necessary between the noise reduction given by balanced lines and the cost introduced by the extra circuitry they require.
Some devices, usually with a transformer output, provide a balanced output that is "floating" with respect to ground; the impedance to ground from each side of the output is high. More commonly, devices drive one or both sides of the balanced interface with a signal referenced to ground. When one side is not driven, care is taken to assure that the impedance to ground is equal to the impedance of the driven side.
Balanced audio connections use a number of techniques to reduce noise.
A typical balanced cable contains two identical wires, which are twisted together and then wrapped with a third conductor (foil or braid) that acts as a shield. The two wires form a circuit that can carry an audio signal.
The term balanced comes from the method of balancing the impedance of each wire in the circuit; the line and all circuits directly connected to it (such as the driver and receiver) must have identical impedances with respect to some reference point. This means that much of the electromagnetic interference will induce an equal noise voltage in each wire. Since the differential device at the receiving end only responds to the difference in voltage between the two signal lines, noise that is identical on both wires is rejected. This method can be implemented with a differential amplifier. A transformer may also be used instead of an active input stage.
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Balanced audio AI simulator
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Balanced audio
Balanced audio is a method of interconnecting audio equipment using balanced interfaces. This type of connection is very important in sound recording and production because it allows the use of long cables while reducing susceptibility to external noise caused by electromagnetic interference. The balanced interface guarantees that induced noise appears as common-mode voltages at the receiver which can be rejected by a differential device.
Balanced connections typically use shielded twisted-pair cable and three-conductor connectors. The connectors are usually three-pin XLR or 1⁄4 inch (6.35 mm) TRS phone connectors. When used in this manner, each cable carries one channel, therefore stereo audio (for example) would require two of them.
A common misconception is that balanced audio requires the signal source to deliver equal waveforms of opposite polarity to the two signal conductors of the balanced line. However, many balanced devices actively drive only one side of the line, but do so at an impedance that is equal to the impedance of the non-driven side of the line. This impedance balance permits the balanced line receiver (input stage of the next device) to reject common-mode signals introduced to the two conductors by electromagnetic coupling.
Many microphones operate at low voltage levels and some with high output impedance (hi-Z), which makes long microphone cables especially susceptible to electromagnetic interference. Microphone interconnections are therefore a common application for a balanced interconnection, which allows the receiver to reject most of this induced noise. If the power amplifiers of a public address system are located at any distance from the mixing console, it is also normal to use balanced lines for the signal paths from the mixer to these amplifiers. Many other components, such as graphic equalizers and effects units, have balanced inputs and outputs to allow this. In recording and for short cable runs in general, a compromise is necessary between the noise reduction given by balanced lines and the cost introduced by the extra circuitry they require.
Some devices, usually with a transformer output, provide a balanced output that is "floating" with respect to ground; the impedance to ground from each side of the output is high. More commonly, devices drive one or both sides of the balanced interface with a signal referenced to ground. When one side is not driven, care is taken to assure that the impedance to ground is equal to the impedance of the driven side.
Balanced audio connections use a number of techniques to reduce noise.
A typical balanced cable contains two identical wires, which are twisted together and then wrapped with a third conductor (foil or braid) that acts as a shield. The two wires form a circuit that can carry an audio signal.
The term balanced comes from the method of balancing the impedance of each wire in the circuit; the line and all circuits directly connected to it (such as the driver and receiver) must have identical impedances with respect to some reference point. This means that much of the electromagnetic interference will induce an equal noise voltage in each wire. Since the differential device at the receiving end only responds to the difference in voltage between the two signal lines, noise that is identical on both wires is rejected. This method can be implemented with a differential amplifier. A transformer may also be used instead of an active input stage.