Working principle of power amplifier

In fact, the working principle of power amplifier is very simple, which is to amplify various sound signals played by sound sources and promote the sound emitted by speakers. From a technical point of view, the power amplifier is like a current modulator, which converts alternating current into direct current, and then it is controlled by the sound signal played by the sound source, and transmits different currents to the speaker according to different frequencies, so that the speaker can emit sounds with the same size and frequency. 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. According to the current demand of audio consumption, power amplifiers in civil audio have been basically divided into two categories, namely pure music amplifiers and home theater AV amplifiers. 1, Pure Music Amplifier The design of pure music amplifier emphasizes the lowest signal distortion, faithfully shows the scene, details, performance and recording skills of music, and meets people's requirements for the best appreciation of music. This is what people often call HI-FI. In the design and production, the requirements of pure music power amplifier are extremely strict. The quality of pure music power amplifier is not entirely determined by its technical indicators. We can't just look at how high the power is, how wide the frequency response is, and how low the distortion is. We should pay special attention to its design and production process and the clarity of music. For example, the courage machine with low technical index is better than many transistor power amplifiers. 2.AV power amplifier generally includes power amplification part and signal processing part. Its power amplifier is no different from the traditional power amplifier in principle, except that several channels are added, that is, several power amplifiers are combined; The signal control and processing part involves the functions of signal audio and video selection, signal decoding processing, signal sound field processing, radio reception and monitoring. Generally, a high-quality AV power amplifier should first have good sound field restoration in the signal processing of film and television programs, high channel isolation, and not too exaggerated atmosphere rendering; Secondly, in the sound quality performance of the power amplifier, especially the sound quality of the main channel, it is required to be as close as possible to a good pure music power amplifier. Classification of power amplifiers Power amplifiers are generally divided into preamplifiers, postamplifiers and combiners. A combiner is a machine that combines preamplifiers and postamplifiers into one. The front stage is used to amplify the signal and adjust the volume. The latter stage is to amplify the signal of the previous stage to drive the speaker. The front desk is also divided into active and passive. The active front stage uses the power supply to amplify the signal, and the passive front stage only has the function of adjusting the volume. To tell the truth, there are not many successful passive front stages at present, because the internal resistance of sound source and rear stage is very different. Only use the volume switch to connect the sound source and the rear stage, and the difference of internal resistance will completely lose the dynamics, details and frequency response! In addition to adjusting the volume, the active front stage can also be used as a buffer to widen the initial part and reduce the internal resistance between the sound source and the rear stage. The rear stage amplifies the signal of the front stage to the loudspeaker, and the rear stage must be strong enough to push the loudspeaker. The so-called enough strength does not mean that the greater the strength, the more powerful it is. Must be able to support the whole band's big scene without losing its details.