【 Weak current College 】 talking about audio cables-Power By 【 China power house network 】

On the audio cable
Whether it's music production equipment or a sound playback device, audio cable has always been an important part, but quite a lot of people do not pay attention to it. This or short or long lines, the rough, has a small core, and all kinds of joints, play audio data transfer, and if a good music playback devices, does not match a proper audio cable, you will not be able to achieve the best playback effect, sometimes even bear to listen to "miserable." 　　This article describes audio cables and related issues, there is only one purpose — to make the best transmit sound signals. Digital audio cable in General, because many digital audio cables use the same with analog audio connectors (such as cards, Lotus mouth agricultural XLR, RCA), many people with analog cable temporary place of digital cable. 　　Although they can improvise, but you must realize that this is very wrong. Analog cable and digital cable is a completely different analog cable impedance requirements, because the length, in cable points, impedance in 30 to 90 Ohm impedance fluctuation between changes, and will not affect the sound quality of analog audio. And this is for digital audio, digital audio signal frequency is very high (approximately 3MHz) of pulse wave, in order to accurately transmit signals, cable must be sending and receiving equipment match, the entire cable impedance must be consistent. 　　For example, AES/EBU cable must be the other end from one end to show constant 110 Ohm impedance, which is also the AES/EBU cable than appearance almost microphone cable expensive many causes. If you are using analog cable temporarily replace a digital cable? first because the impedance mismatch, the cable will have a standing wave reflection, "pollution" signal, the outline of the pulse wave. Pollution also from cable distribution capacity, it can reduce cable of high-frequency response, impact pulse rise time. 　　Pulse waveform in high and low voltage conversion defined out signal 0 and 1, if you were not the correct impedance and capacitive effects has been polluted, pulse signal, the receiver of the signal interpretation error occurs, a time before and after the offset (called a flutter, Jitter), which reduces the audio quality, even wrong code appears. Making computer music cannot be separated from the rest of the audio cable, they do not have a microphone, synthesizers, sound mixer, za, and other equipment that has a striking appearance, often looks like spread all over the floor. The average user on the device, compare careful careless, connecting cable comparison on the line, not much attention to quality. If all devices are generally lower, cable digital out insufficient also; if Studio equipment is advanced, low-quality cable became the sound of the "bottleneck", we will follow it degraded. 　　Then replace the cable investment is necessary. Analog audio cable analog audio cables can roughly be divided into three categories: microphone cable, guitar/line cable and loudspeaker cables. Typically, the center part of the audio cable is a conductor, is the carrier of the audio signal. Conductor outside covered with non-conductive plastic or rubber, and the outside is made up of a conductor, which on the one hand, the shield is isolated from the external interference, on the other hand, constitute a signal ground wire (loop). The outermost layer of the skin can protect the internal layers so that the cable is durable. Audio cable for general use copper conductor, because it cost low, the electrical conductivity is good, more flexible. 　　However exposed to air oxidation of copper easily and become poor conductor copper oxide, affect current conduction. Analog audio cables use the typical form of several patch, microphone typically use card administrative (XLR), line connections using large three-core (1/4 inch) or Lotus mouth (RCA), speaker cable connector often bare copper wire, sometimes with banana plugs or other plugs. 　　Plug and socket binding, full ductility of gold-plated layer can fill the gap in the connection, keep the good connections. Cable shielding requirements for many types of interference can affect the cable in the audio signal transmission, so the cable needs to have good shielding. Common type of interference from radio signal, the English abbreviation for Radio-Frequency Interference, RFI. Cable if you pick up the radio emission of the signal, after amplification circuit, it may be detecting mixed audio amplification and signal which cause interference. Shielding of cables as an antenna, can easily be ubiquitous radio interference. RFI is a kind of electromagnetic waves, electromagnetic interference sources belong also motor coil, fluorescent lights, neon lights, etc. Other common types of interference is called static (Electrostatic) interference from electrical discharge, electrostatic discharge, etc.
Cable's shield to protect the Center conductor from these types of interference, but screen on some types of electromagnetic waves is invalid, the balance transfer can only be used to offset their way (so that the two conductors, pick up the same interference, through transformer two interference signal in the opposite direction, the aim of achieving mutual cancellation). 　　Shielded wire is mainly used for microphones, guitars, line cable, because these signal source levels are relatively low and needs to be expanded, and in broadening the signal at the same time, mixed into the interference signal will be magnified, with serious consequences. Speaker cable delivery of high level signal interference signal, compared to negligible, there is no need for a shield, but the speaker cable has its own requirements. Such as conductor resistance for microphone cable not very important, but the speaker cables to pass high-current, the impedance is very prominent, in principle, the shorter the crude and better. It is important to note that the speakers are also equipped with a line end second core or Canon plug, with the microphone line, sometimes even look the same. 　　But they are completely different, some cables do not confuse or mistyped. Resistance, capacitance, inductance, resistance, resisting resistance including capacitance, inductance, resistance to Ohm units. A good understanding of resistance, electrical conductivity of various materials, the same material as the diameter and length are different and have different resistance. For example, 500 feet, wire gauge copper resistance is 4 ohms, wire gauge, increase or decrease each of the 3 numbers, resistance to double or halve. 500 ft 13, wire gauge copper resistance 2 ohm, 19 wire gauge 8 Ohms of resistance, and so on. Such a small resistanceThe effect of the change for speakers. Speaker impedance generally within 2 to 8-Europe, if we use a 4-impedance speaker, cable impedance is 4 euro, together they become 8-Europe, and only half of the power delivered to the speaker, the other half totally consumed in cable! many high quality speaker cable with sufficient diameter (12 to 18AWG) and of medium length (less than 100 feet), and count up, even with 18 line, there is still a 1.3 Ohm resistor, lines will have some power loss. In the microphone cable, capacitance ratio resistance more problematic. 　　In the insulation of two metal objects can form a capacitor, the audio cable of the shield and inner conductor just such a relationship, therefore the entire cable to form one large Capacitance to its capacitance blocking the flow of AC current. According to the nature of the capacitance, frequency increase makes the capacitance decrease, however this capacitance and resistance of the cable, will form low-pass filter, cable length, the greater the cut-off frequency point down, attenuation. This is generally recommended that no important reason too long cables. Conductor of another property is inductive reactance. Audio signal wires in circulation produced with a voltage variation of magnetic field, physics is known as the "perceived". 　　This magnetic field on the signal through the problem, it reduced the frequency and smaller, and resistance, capacitance interaction produces complex results. In the line level circuit, due to the current weak magnetic self-induction have also not strong; however large current signal (such as the speaker signal) of the magnetic field is much more powerful. Use high-quality speaker cable can reduce the magnetic self-induction, improve sound quality.