There are many devices used in the audio system. Devices come in different interface forms with balanced and unbalanced input and output forms. In order to effectively shield external electromagnetic radiation and interference, shielded cables must be used uniformly and the correct connection method must be adopted.
When the audio signal transmission is balanced, the external interference power supply generates a common mode interference level equal to the ground loop for the two signal lines in the cable. At the input end of the internal amplifier of the device, the common mode voltage on the two signal lines will be replaced by the differential mode voltage and cancel each other, which will not form the interference voltage. Therefore, a balanced connection method should be used whenever possible.
When connected to an unbalanced output device. Instead of a balanced-unbalanced converter, use a single-core shielded cable to connect the ports of the balancing device to the ports of the unbalanced device. The noise induced by the shield is mixed into the audio signal, which increases noise, which is a major way to introduce noise. Therefore, for balanced or unbalanced transmissions, a double-core shielded cable should be used and the shield should be grounded only at the end of the balanced output or input.
When the two ends are unbalanced devices, if the transmission distance is long, it is better to use a balanced, unbalanced converter or audio isolation transformer to convert to balanced transmission.
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