In the sound engineering, the wire must be used. In fact, the selection of wire is also very important. If the wire is poor, such as signal loss and distortion will occur. We all know that the signal transmission between analog and digital equipment in audio equipment system must be interconnected by wire. No matter what system type and format of system equipment is used, the wire materials used are very critical. Sometimes, in a certain link, the AC characteristics of cables, the transmission characteristics of various purposes, and the characteristics of interconnecting plug-ins between cables and equipment with different purposes are ignored. No matter how good the equipment is, without a reasonable combination of audio cables and connectors, the best effect of the equipment cannot be achieved. Therefore, how to correctly select the required wire rods is very important.

1. Digital audio cable

Common digital audio cables can use the same connectors as analog audio cables, such as XLR, RCA, BNC, etc. Of course, using analog cable instead of digital cable can also transmit signals, but it will affect the transmission quality.

The output impedance and cable impedance of analog cables and digital equipment have strict requirements. No matter how long the analog cable is, the impedance at each point of the cable is 600 Ω. When the input and output impedance of the analog equipment is less than 600 Ω during level matching, the sound quality of the analog audio will not be affected. If it is used for digital audio equipment, it is different. Digital audio signal is a pulse data stream with high working frequency. In order to transmit signal accurately, the cable must match the transmitting and receiving equipment, and the impedance from the beginning to the terminal cable must maintain a uniform standard.

If the cable of analog equipment is used to replace the digital cable on the digital equipment, its characteristic impedance does not match. Because the frequency of the digital electrical signal is very high, the skin effect of the current on the wire will be deeper when the characteristic impedance matches, and the deeper the transmission effect is, the better. In case of mismatch, the shallower the skin will be, the worse the transmission effect will be. This is because most of the current in the cable forms reflection, which will generate standing wave and consume signal energy, causing distortion of digital pulse signal waveform. Because the distributed capacitance, distributed inductance and resistance in the cable can directly affect the frequency response in the signal and the rising and falling edge time of the pulse when the cable impedance does not match (that is, when the symbol is "1" or "0", there is a level jump at the beginning and end of each data bit cycle, and the mismatch will affect the complete level jump), error code will occur when interpreting digital signals at the transmission and reception ends, If the rising edge time and falling edge of the pulse are shifted back and forth in time, the jitter time will be long and the audio quality will be degraded, and even noise will be generated to degrade the audio quality.

When recording and producing all kinds of programs, audio cables are required for the combination of audio system equipment. In addition to the digital mixer, there are many digital analog peripheral equipment, such as all kinds of microphones, equalizers, time delay devices, effectors, synthesizers, D/A converters, audio processors, digital recording and playback equipment, monitoring speakers and other equipment. It is often considered that the connection is OK, ignoring the program quality transmission indicators. If the technical indicators of the equipment used are not high, the deficiencies of the cable will not be revealed; If the equipment indicators in the recording room are all classified equipment, the application of impedance matching cable has become an important link that can not be ignored to meet the audio indicators. In order to achieve this result, the transmission cable matching the equipment must be used, and at the same time, the input and output levels of the equipment must be reasonably matched.

2. Analog audio cable

Analog audio cable can be roughly divided into microphone cable, transmission line cable and speaker cable. Audio cable has single core, two core and three core. The core wire is the conductor of audio signal; The outer layer of the conductor is a metal wire with a shielding layer composed of woven mesh and the outer skin of the protective layer, which can shield external electromagnetic interference, and can also be used as a signal ground. The outer layer of the shielding layer is covered with non-conductive plastic or rubber, which acts on the tensile resistance of the inner conductor shielding wire, and also protects the shielding layer from corrosion; The outermost outer layer can protect the inner layers, making the cable durable.

The skin effect is also considered for audio cables. Generally, silver or tin plating on the copper wire surface is used as the conductor because of its low cost, good conductivity and ease of movement.