Balanced and unbalanced transmission of audio signals
Balanced transmission is a very widely used audio signal transmission method. It uses the principle of phase cancellation to minimize other interferences experienced during audio signal transmission. It needs three parallel wires to realize, namely grounding, hot end, cold end. Therefore, the balanced input and output plug-ins must have 3 pins, such as Canon or three-core plug-in (see Figure 1).
(Picture 1) (Picture 2)
The transmission line must of course also be a 2-core, 1-shielded line. Since the hot-end signal line and the cold-end signal line are relatively close in the same shielding layer, other interference signals received during the transmission process are also almost the same. However, the phases of the transmitted hot-end signal and cold-end signal are opposite (as shown in Figure 2), so the hot-end signal and the cold-end signal are subtracted at the input of the next stage of the device, the same interference signal is cancelled, and the transmitted signal No loss due to the opposite phase. Therefore, the balance transmission method is usually used in professional occasions and when the transmission distance is relatively long.
2. Unbalanced signal transmission
Unbalanced transmission has only two terminals, the signal terminal and the ground terminal. It is used in occasions where signal transmission is not demanding and at close range, such as a home audio system. This connection is also commonly used in electronic musical instruments, electric guitars and other equipment.
Three, DI box
DI was originally intended for direct input, and was designed for electric guitar direct input mixers. The balanced input terminal of a general mixer is designed for a dynamic coil microphone of 600 ohm, while the output impedance of an electric guitar is above 100Kohm and is not a balanced output. Therefore, the DI box is used to solve this problem, so the DI box has two functions of impedance matching and unbalanced signal to balanced signal. If an effect device is connected between the electric guitar and the mixer and the transmission distance is not very far, then the output of the effect device can be directly input into the LINEIN of the mixer without connecting the DI box.
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