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Power amplifier is commonly known as "amplifier". Its function is to amplify the weak signal from the sound source or preamplifier and push the speaker to make sound. A good set of audio system power amplifier plays an important role. The power amplifier is the most basic equipment in the audio system. Its task is to amplify the weak electrical signal from the signal source (from the mixer in the professional audio system) to drive the speaker to make sound. Power amplifier, referred to as power amplifier, can be said to be the largest family of all kinds of audio equipment. Its main function is to amplify the weak signal input by audio equipment and generate enough current to push the speaker to play back the sound. Considering the differences in power, impedance, distortion, dynamics, application scope and control and adjustment functions, different power amplifiers have different internal signal processing, circuit design and production technology. Power amplifiers can be divided into Class A (also known as Class A), Class B (also known as Class B), Class A and B (also known as Class AB) and Class D (also known as Class D) according to the different conduction modes of power amplifiers. Class A power amplifier refers to an amplifier in which any power output element of the amplifier will not be cut off (i.e., output will stop) during the whole period of the signal (plus or minus two and a half periods of sine wave). Class A amplifier will generate high heat and low efficiency when working, but its inherent advantage is that there is no cross distortion. Single-ended amplifiers all work in Class A mode, and push-pull amplifiers can be Class A, Class B or Class B. Class B power amplifier refers to an amplifier in which the positive and negative two half periods of a sinusoidal signal are amplified and output by two "arms" of a push-pull output stage in turn, and the on time of each "arm" is half a period of the signal. The advantage of class B amplifier is high efficiency, but the disadvantage is that it will produce crossover distortion. Class A and Class B power amplifiers are between Class A and Class B, and the on-time of each "arm" of push-pull amplification is longer than half a period of the signal and less than one period. Class A and Class B amplifiers effectively solve the cross-distortion problem of Class B amplifiers, and their efficiency is higher than that of Class A amplifiers, so they are widely used. Class D power amplifier, also known as digital amplifier, uses extremely high frequency switching circuit to amplify audio signals, which has the advantages of high efficiency and small size. Many class D power amplifiers with power as high as 1000W are as big as VHS video tapes. This kind of amplifier is not suitable for broadband amplifier, but it has many applications in active subwoofer. According to the number of amplifying elements in the output stage of power amplifier, it can be divided into single-ended amplifier and push-pull amplifier. The output stage of a single-ended amplifier consists of an amplifying element (or a plurality of parallel elements) for amplifying positive and negative signals for two and a half periods. Single-ended amplifier can only work in class A.. The output stage of push-pull amplifier has two "arms" (two groups of amplifying elements). When the current of one arm increases, the current of the other arm decreases, and the states of the two arms alternate. For the load, it seems that an "arm" is pushing and an "arm" is pulling, and * * * has completed the current output task. Although Class A amplifiers can use push-pull amplification, it is more common to use push-pull amplification to form Class B or Class B amplifiers. According to the different types of power amplifier tubes in power amplifier, it can be divided into courage machine and stone machine. Courage machine is a power amplifier using electron tubes. Si Tong Machine is a power amplifier using transistors. According to different functions, preamplifier (also called pre-stage), power amplifier (also called post-stage) and combined amplifier can be used. Power amplifier, referred to as power amplifier, is an electronic device used to enhance signal power to drive speakers. Power amplifier without auxiliary functions such as signal source selection and volume control is called post-stage. Preamplifier is the pre-amplification and control part before the power amplifier, which is used to enhance the voltage amplitude of the signal and provide input signal selection, tone adjustment and volume control. Preamplifier is also called pre-stage. An amplifier that installs a preamplifier and a power amplifier in the same box is called a combined amplifier. The common power amplifiers in our family are generally combined. According to different purposes, it can be divided into AV amplifier and Hi-Fi amplifier. AV power amplifier is a power amplifier specially designed for home theater, which generally has more than four channels and surround sound decoding function, and has a display screen. The main purpose of this power amplifier is to really create the sound effect of the movie environment and let the audience experience the cinema effect. High-fidelity power amplifier is a kind of amplifier specially designed to reproduce the true color of music with high fidelity. Generally, dual-channel design is adopted, and there is no display screen. According to the different components used, the power amplifiers include "Bold" [electronic tube amplifier], "Stone" [transistor amplifier] and "IC amplifier" [integrated circuit amplifier]. In recent years, due to the application of new technology and new concepts in the gallbladder machine, the electronic tube, an ancient vacuum device, shines brilliantly, and its beautiful sound makes many fans fall in love. Almost all experienced enthusiasts have one. "IC power amplifier" is rarely seen in HI-FI power amplifier, because its timbre is not as good as two power amplifiers. Power amplifiers can generally be divided into three categories: professional power amplifiers, civil power amplifiers and special power amplifiers. "Professional power amplifier" is generally used for sound reinforcement in conferences, performances, halls, auditoriums, stadiums and museums. The design is based on high output power, perfect protection circuit and good heat dissipation. When the timbre of most "professional power amplifiers" is used for HI-FI playback, the sound is very unpleasant. The detailed classification of "civil power amplifier" includes "HI-FI power amplifier", "AV power amplifier" and "KALAOK power amplifier" which integrates various common functions. "HI-FI power amplifier" is the power amplifier of our enthusiasts, and the output power is generally below 2X 150. The design aims at "beautiful timbre and high fidelity". All kinds of high and new technologies are embodied in this power amplifier. Prices also range from 1,000 yuan to several hundred thousand yuan. High-fidelity power amplifiers can be divided into two types: split power amplifier (which separates the former power amplifier) and combined power amplifier (which combines the former power amplifier and the latter power amplifier into one). Generally speaking, the "splitter" is higher than the "combiner" in terms of signal-to-noise ratio, channel division and other indicators. And it is easy to compare sounds through signal lines. The invention has the advantages of convenient use and relatively low cost. The output power of even-odd combiner is generally designed to be below 2X 100W, and many manufacturers produce high-grade combiner with 2x 100 W or above ... "AV" power amplifier is a runaway dark horse in recent years. With the popularization of large-screen TV and various image carriers, people's demand for "sitting at home and watching movies" is increasing day by day, and multifunctional power amplifiers with various audio and video functions have emerged. "AV" is the initials of English AudioVideo, that is, audio and video. "AV power amplifier" has experienced the process of Dolby surround, Dolby directional logic, AC-3 and DTS since its birth. The difference between AV power amplifier and ordinary power amplifier is that AV power amplifier includes AV selective Dolby directional logic decoder, AC-3, DTS decoder and five-channel power amplifier. And the digital sound field [DSP] circuit, which makes the finishing point, provides different sound field effects for various programs. However, because the AV amplifier has gone through too many complicated processing circuits in the signal circulation of the circuit, the sound purity has been "stained" too much, so the effect is not ideal when it is compatible with HI-FI playback with AV amplifier. This is also the reason why many HI-FI enthusiasts ignore the AV amplifier. "KALAOK power amplifier" is also a kind of power amplifier developed in recent years. The difference between it and general power amplifier is that "KALAOK Power Amplifier" has reverberators, which have developed from BBD analog reverberation to DIGETAL digital reverberation, modulators and microphone amplifiers. In recent years, in order to meet the market demand, some manufacturers have combined various functions such as AV amplifier and KALAOK amplifier into one, which is the so-called "integrated amplifier". This is a hodgepodge amplifier that has everything and can't do anything well, and it is a kind of resistant amplifier.