subject: Know The Difference Between Balanced And Unbalanced Cables [print this page] An unbalanced cable has two wiresAn unbalanced cable has two wires. The live wire lies along the center of the cable. It is surrounded by insulation. Around the outside of this insulated live wire, there is another wire. This outer wire is braided and acts as the earth wire. Further insulation is placed around the earth wire. Unbalanced cables typically have either phono or 1/4 inch jack plugs. The live wire transmits the audio signal while the earth wire protects it from electrical interference from the environment.
Balanced cables have three wires, separate live and return wires, and an earth wire. The live and return wires carry the audio signal, while being shielded by the earth wire. Balanced cables usually have XLR, 1/4 inch jack or bantam jack plugs.
Unbalanced cables cannot carry phantom power. This power is used by many pieces of equipment to remove the need for a separate power cable. Only balanced cables can transmit the phantom power, because it requires two separate wires. The power and audio signals do not interfere with one another, because they travel in opposite directions along the wires. The live wire for the audio signal is the return wire for the power.
Unbalanced wires are not suitable for carrying weak, quiet microphone signals. In a long unbalanced cable, the earth wire is unable to shield the signal from all interference. Long unbalanced cables can also suffer from loss of high frequency audio signals. All electrical interference is eliminated in a balanced cable, regardless of the length, and the loss of high frequency audio is much lower than that experienced with an unbalanced cable.
The signal from a microphone passes through a transformer that sends it along the live wire of the balanced cable. At the same time, the transformer creates a negative or phase inverted copy of the audio signal, which it sends along the return wire. As the two signals pass along the wires, any electrical interference from the surrounding environment affects both signals by the same amount. At the other end, the two signals pass through another transformer. This second transformer reverses the phase of the return audio signal, returning it to its original form. The interference that affected the return signal is, therefore, separated or put out of phase with the return. The live and in-phase return signals are then combined to create a strong signal. The interference from the return wire remains out of phase with the interference from the live wire. This means that when the two signals are combined, the interference signals are canceled out by each other. They disappear, leaving only the audio signal.
