On Audio Wire

In terms of audio cables, in the audio industry, in addition to equipment such as power amplifiers, speakers, sound sources, etc., they are also very particular about signal connection cables. The price of each line is in the high price of one hundred yuan to one thousand yuan or even ten thousand yuan. For words, it is considered a great waste to invest money and energy on the wire in order to improve the sound quality. The improvement of the sound quality by the wire is very small, and it is seriously unbalanced compared with its price. So how much does the signal line affect the sound quality? I'm not an audiophile, so I don't have a fanatical fascination with wires, but I also deny the uselessness of wires. I will discuss my views on audio wires with a pragmatic attitude. Any transmission cable can be equivalent to a distributed system composed of resistance, capacitance and inductance. Due to the presence of capacitance and inductance, the transmission cable has its special frequency characteristics, that is, different delays for signals of different frequencies (also That is, so-called different transmission rates) and different impedances. Obviously, this will cause some distortion of the signal. In addition, the resistance of the cable will also cause loss of the signal, but because the audio signal connection line is usually relatively short, this loss can be ignored. However, the speaker cable cannot be ignored because the cable between the amplifier and the speaker is long and the power transmitted is large. The resistance of the cable will directly affect the output stage of the amplifier (the load impedance becomes larger). Another important parameter of the transmission line is the characteristic impedance. Although the small signal in the audio electronic circuit is connected, the impedance matching is not as particular as the high-frequency circuit or the large-signal circuit, but if the difference is too large, it will affect the timbre of the playback. . The sound sources of the audio amplifier are roughly: radio head, tape head, CD player, record player, etc. The output impedance of these sound sources is different, so the characteristic impedance of the wire should be close to the output impedance of the sound source equipment when mating. We can divide the signal line into strong signal line, weak signal line and standard signal line to discuss separately: 1. Strong signal line refers to the connecting line between the speaker and the power amplifier. Such lines often have no shielding layer. The key is to reduce its resistance, because the output resistance of modern power amplifiers is very low, so the requirements for the speaker cable also increase, such as the use of large cross-sectional area or multiple stranded wire. The wires are available from pure copper to silver wires. A relatively expensive speaker wire is a dedicated wire for oxygen-free copper speakers. Its main characteristics are good conductivity and low resistivity. When it is used, the sound tone does not increase when replaying the sound. less. Because the transmission line has different impedances to signals of different frequencies, this characteristic appears to be blurred in the reproduction of sound. For this reason, people have produced a high-end speaker connection line called an intelligent signal line. The characteristics of this line The signal is divided into two channels according to the frequency level. The outer layer of a certain thickness passes the signal above 5KHZ, and the signal below 5KHZ is transmitted through the inner layer of the line. This greatly improves the frequency characteristics of the transmission line and makes the replay The sound is clear and transparent. However, if your amplifier output power is small or the speaker cable is short, do n’t spend the money on this expensive wire. In this case, the effect is not outstanding. 2. The weak signal line refers to the connection between the microphone and the preamplifier, which is usually a shielded line. 3. The standard level signal line refers to the connection line between the sound source and the power amplifier. Its transmission level is about 1V, and it is also a shielded transmission line. This kind of wire is the most widely used in the audio industry. What is interesting is that wires made of different insulating media and metal materials have a subtle effect on the sound quality. For this reason, manufacturers have produced various types of wires to meet people ’s Different levels of music appreciation. The high-end finished wire is made of nylon braid coated with anti-static layer as the outer layer, lined with metal shielding sleeve and then oxygen-free pure copper as the core wire, and then equipped with a gold-plated plug to prevent the plug from contacting and generating noise. Brands of standard-level signal wires are: American MONSTER STANDRDINTERLINK (monster), AUDIO0UEST (line sage), SUPRA (tortoise), M0NITERPC (magic), SPACE & TIME (time-out space), MISSION (Baisheng), PATRDNICS (Bai Li) and many more. Japan's MAKURAWA (Mellow), DENK0 (Climb), PATRD NICS (Bai Li) and so on. Japan's MAKURAWA (Mellow), DENK0 (Ascend), 0SONIC (Osonic), PC 0 CC (Furukawa), ACROTEC (Japan Mining), HISAGO (Sansha), Lux, Golden Throat, etc., and Europe PHILIPS (Netherlands-Philips), VDH (Netherlands-Wandenhall), IXOS (United Kingdom-Aethos), 0RT0F0N (Denmark-high wind), etc., these lines are nothing more than the use of different production materials and processes To achieve the purpose of changing the frequency characteristics to improve the sound quality of the playback, at best it only plays a role in improving the expressiveness of the music. If you are not a music fan or your power amplifier is too low, you should not spend money to buy these expensive audio cables, because if your amplifier is inherently inadequate for music performance, use ordinary cables and expensive Price wire effect is the same. According to one of my audiophile enthusiasts, if your amplifier price does not exceed 20,000 yuan, the use of expensive cables will not show any effect on improving the sound quality. In summary, for a set of audio system, the selection of standard level signal wires only has an auxiliary effect on the sound quality. Expensive audio wires can only love the expensive amplifiers. According to the size of the output power to choose the right speaker cable is the most practical. The main points of the thinking draft about the distortion of the audio amplifier. Recently I saw an article on the page 199 of the 2002 e-newsletter volume titled "Talking about the distortion of audio amplifiers and common improvement methods". I think this article is well written. Worth a look for electronics enthusiasts, I will write the main points of this article for your reference. Distortion is the phenomenon that the input signal and the output signal change in amplitude proportional relationship, phase relationship and waveform shape. The distortion of audio power amplifier is divided into two categories: electrical distortion and acoustic distortion. Electrical distortion is caused by the circuit, and acoustic distortion is caused by the speaker of the sound-returning device. The types of electrical distortion are: harmonic distortion, intermodulation distortion, transient distortion. Acoustic distortion is mainly the distortion of the AC interface. According to the nature, there are nonlinear distortion and linear distortion. Linear distortion refers to the change in the amplitude and phase relationship between the frequency components of the signal. Only the amplitude and phase distortion of the waveform appear. The characteristic of this distortion is that no new frequency components are generated. Non-linear distortion refers to the distortion of the signal waveform and the generation of new frequency component distortion. The main points of distortion generated by the audio amplifier are as follows: 1. Harmonic distortion This distortion is caused by nonlinear components in the circuit. After the signal passes through these components, new frequency components (harmonics) are generated. These new frequency components Interfering with the original signal, this distortion is characterized by the inconsistent shape of the input signal waveform and the output signal waveform, that is, the waveform is distorted. The main ways to reduce harmonic distortion are as follows: 1. Apply appropriate amount of negative feedback. 2. Amplifier devices with high characteristic frequency, small noise figure and good linearity are selected. 3. Improve the power reserve of the power supply and improve the filtering performance of the power supply. Second, intermodulation distortion Two or more signals of different frequencies pass through an amplifier or speaker to produce a beat and constitute a new frequency component. This distortion is usually generated by active devices in the circuit (such as transistors and tubes) . The magnitude of the distortion is related to the output power. Since these newly generated frequency components have no similarity to the original signal, less intermodulation distortion is also easily noticeable by the human ear. Methods to reduce intermodulation distortion: 1. Use electronic frequency division to limit the working bandwidth of the amplifier circuit or speaker, thereby reducing the occurrence of beats. 2. Choose a tube or circuit structure with good linearity. 3. Transient distortion Transient distortion is an important indicator of modern acoustics. It reflects the ability of the power amplifier circuit to keep track of transient transition signals, so it is also called transient response. This kind of distortion makes the music lack level or transparency. There are two forms of expression: A. Transient intermodulation distortion. When a pulsed transient signal is input, due to the capacitance in the circuit, the output terminal cannot get the proper output voltage immediately, and the negative feedback circuit cannot get a timely response. The amplifier is in an open-loop state at this moment, making the output momentary Clipping occurs due to overload. This clipping distortion is called transient intermodulation distortion. This distortion is more serious on stone machines. Transient intermodulation distortion is a dynamic indicator of the power amplifier, mainly caused by deep negative feedback inside the power amplifier. It is the culprit that affects the sound quality of stone machines and causes "transistor sound" and "metal sound". The main methods to reduce this distortion are: 1. Choose good devices and adjust the operating point, try to improve the amplifier's open-loop gain and open-loop frequency response. 2. Strengthen the negative feedback of each amplifier stage and cancel the negative feedback of the large loop. B. Distortion caused by low conversion rate. As mentioned above, high-level input pulses cause the amplifier to clip and cause transient intermodulation distortion. Will low-level input pulses cause distortion? This depends on the response time of the amplifier. Because the response time of the amplifier is too long, the change in the output signal of the amplifier cannot keep up with the rapid change in the input signal, which is called the slew rate distortion. It reflects the reaction speed of the amplifier to the signal. This low-distortion amplifier has good resolving power, layering and positioning. 4. Distortion of AC interface Distortion of AC interface is caused by the feedback of the back electromotive force of the speaker (the electric potential generated by cutting the magnetic force lines when the speaker sounds vibrating) to the circuit. The improvement methods are: 1. Reduce the output impedance of the circuit. 2. Choose the right speaker to make the damping coefficient more reasonable. 3. Reduce the internal resistance of the power supply.
Technical area detailed analysis of Doherty power amplifier design load traction principle (top) detailed analysis of Doherty power amplifier design how to improve efficiency (bottom) analysis of voltage follower input and output error analysis Solve the effect of power amplifier on emi

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