Several technical indicators to pay attention

Notes on purchasing AV amplifier As the central link of the home system, the AV amplifier is a very important link between the DVD player and the speakers. Its price should account for between 25-30% of the total investment in a home theater. 1. Features Function is one of the first concerns of consumers. When purchasing an AV amplifier, it is necessary to clearly understand what functions the amplifier contains, because the amplifier cannot be ignored except for its function of signal amplification. For example, audio signal input terminals need attention, and general AV amplifiers provide CD, LD, TV, DVD, VCR1, VCR2, and CDR, and some provide settings such as MD and LP. Of course there is an output when there is an input, and the importance of the output terminals cannot be ignored. For example, the number of output terminals such as optical fiber and coaxial. So before you buy, be sure to read the description of the manual clearly, you must know what features you need. And there are some AV amplifiers with radio function, it depends on your needs. Some amplifiers are also equipped with some more special functions. So before buying, it is necessary to understand the AV functions and those commonly used functions. 2. performance The performance of a machine has a lot to do with its quality. So how to know the performance of the AV amplifier you choose? To understand the quality of the products you buy, you must try it yourself. If you are unfamiliar, it is best to bring a friend you know. Try to choose some more famous products, not blindly pursuing so-called imported products, because there are too many fake foreigners on the market. Imports are the same as domestic ones, and you have to choose a well-known brand. And you must actually operate the machine once before buying to understand the performance of the machine. 3． parameter The next thing to note is the parameters of the AV amplifier. The parameters are for reference only. You don't have to be overly blind to think that the higher the value, the better, and the lower the value, the better. Moreover, some brands only provide some misleading peak parameters. For ordinary consumers, it is not surprising that they do not know how to do so. In addition, when purchasing an amplifier, it must be matched with the speaker system. If it is allowed, it is best to pair it with the speaker you are using or the speaker you plan to buy. When purchasing an AV amplifier, you must also clearly understand the power of the amplifier, because this has a lot to do with the environment. The use environment is large, and the amplifier needs to have a certain output power to ensure that sufficient current is provided to drive the speaker to prevent the speaker's driving force from being insufficient. On the other hand, the maximum output power of the amplifier must be matched with the maximum power of the speaker to prevent the speaker from being accidentally burned. 4． Sound quality After meeting the most basic considerations above, the final important link-sound quality. Because what parameters are well spoken and how complete. Amplifiers are ultimately used to restore sound. The sound quality is not good, do we still need it? What we want is not something that emits noise after moving home. So no matter how much preparation you make before purchasing an AV amplifier, it is necessary to audition in person. Many times, the sound of the amplifier has a certain personality, and the sound matched with the speaker may not necessarily be good. So not only should you audition in person, but it is best to connect the amplifier to the speaker system you choose in the field. How to buy an amplifier Buying an amplifier is an important part of assembling an AV system. Excluding TVs or projectors, the price should account for (30-35)% of the total investment in a home theater. When purchasing the power amplifier, it should be matched with other equipment (such as speakers, video players, CD players, etc.), and the cost performance and appearance should also be considered. It must have many functions, good performance, and save money, and the appearance is satisfactory. Here are some issues to pay attention to when purchasing an amplifier. 1.Analysis Manual It is necessary to study the manual carefully, analyze its main performance indicators and related functions, and pay more attention to the three technical indicators of output power, harmonic distortion and frequency response. At present, there are many types of output power, especially the definition of some powers is not clear, and the measurement methods are not uniform. You must pay attention to the conditions under which the output power is measured and not be confused by the surface advertising data. Also note that the larger the power value is, the better it is. It is not necessary to use too much power in ordinary households; the output power is related to frequency response and harmonic distortion. You should choose a wide frequency response, small harmonic distortion, and output power. Also relatively large power amplifier. The marked frequency response and harmonic distortion must also be analyzed. For example, the selling price is relatively low, and the harmonic distortion is claimed to be 0.001%. This distortion is an excellent value and must be false. When selecting an amplifier, it must be matched with the speaker system. On the one hand, it is necessary to consider how many speaker systems are installed in the listening room. The simplest amplifier has only 1-2 channels of power output, and it can be configured with the simplest two-channel stereo system. The more complex amplifiers must be configured with 4-6 channels. For power output, you must set up two front main channel amplifiers, but also match the center channel amplifier and surround channels, and even set the output port to match the subwoofer amplifier. On the other hand, the maximum output power of the amplifier must be matched with the maximum power of the speaker to prevent the speaker from being accidentally burned, and at the same time to prevent the speaker's thrust from being insufficient. The above situations must be considered in advance. 2. Research on electronic circuits When purchasing power amplifiers, try to hire someone who is familiar with electronic circuits as a staff to analyze the advantages and disadvantages of the circuit. Many power amplifier circuits (especially transistor machines) are very particular about them now, and they use high-quality circuits. For example, the input stage adopts a common-emitter-common-type differential circuit. After the emitter constant current source is set in the first stage circuit, the common touch suppression ratio of the whole machine is greatly improved; the voltage amplifier stage also uses a differential amplifier. The impedance matching of the front and back stages is achieved, and the passband of the circuit is widened. The power output stage uses complementary symmetrical circuits. Various measures are used to reduce distortion, widen the passband, increase the output power, and also add necessary protection measures. Speaker protection circuits are often set; on power circuits, ring transformers, double-bridge high-speed rectifier circuits are often used, and large capacitors of tens of thousands of microfarads are set. The selection of these circuit structures and components is conducive to improving the performance indicators of the power amplifier. However, it is not enough to see these, you should look more deeply into each part of the circuit. For example, in terms of power output circuits. In terms of power supply and so on. When choosing an amplifier, don't pay too much attention to its functions, as long as it meets the basic requirements. If an ordinary price power amplifier has all the functions that people care about, it will not be able to work hard on the power output index. It can only do all aspects of the function to a general level, the music effect is not ideal , And easily cause mutual interference between various parts of the circuit. 3. Try it yourself After the above two steps are basically satisfactory, you must audition in person, this link must not be missed. Sometimes the indicators and circuits marked on the manual are better, but the audition effect may not be good. The reason is that many indicators are test results under sine wave conditions, and actual music and singing are very complicated. In addition, the connection and matching of the power amplifier and the speaker is also an important issue. Sometimes the power amplifier and the speaker have their own personalities. After matching together, they can learn from each other's strengths. If the amplifier can be connected to the speaker system of your choice in the field, the field audition will definitely make the buyer feel relieved.