Introduction to the basic knowledge of power amplifier

                             Introduction to the basic knowledge of power amplifier

Professional amplifiers need to work continuously for a long time during large-scale events, and they must also be able to withstand the vibration and impact of handling. Therefore, compared with general audio amplifiers, professional amplifiers pay more attention to durability and structural reliability for long-term use in design. Amplifiers have an important impact on the sound quality of sound reinforcement, accounting for about 30% of a complete set of audio equipment. Therefore, in order to give full play to the performance and function of audio equipment, we must pay attention to the quality of the amplifier. Otherwise, a high-quality sound reinforcement system cannot function.

There are three types of power amplifiers: 1. Monolithic power amplifier; 2. Integrated mixer + power amplifier; 3. Integrated speaker + power amplifier.

Monolithic amplifier: This power amplifier is an independent component, which can be combined into a sound system according to one's own plan. Generally, a power amplifier consists of two channels.

Mixer + power amplifier integration: This kind of power amplifier is easy to connect and easy to operate, and is often used in small and medium-sized sound reinforcement systems.

Power amplifier + speaker integration: Because the matching of power amplifier and speaker is considered, it is simple and convenient to use, and it is mostly used for monitor speakers and keyboard speakers.

When the amplifier is connected to the amplifier and the amplifier is connected to the Yangzhi device, the impedance matching between them must be considered (the impedance is in ohms). Impedance matching means that the rated output impedance of the power amplifier should be equal to the rated impedance of the speaker. At this time, the speaker absorbs the most power. If the rated impedance of the speaker is much smaller than the rated output impedance of the power amplifier, it will cause a sharp increase in the operating current, which will damage the speaker and amplifier. When one channel of the power amplifier drives two speakers, the total impedance of the speakers will become smaller, and then the load impedance value of the power amplifier will become smaller, and the power amplifier will be overdriven in a near-short circuit condition. Therefore, when the power amplifier is connected with the speaker, it must be noted that the input impedance value of the speaker must be within the load impedance range of the power amplifier.

Power matching: In principle, the rated output power of the power amplifier should be equal to the rated power of the speaker, but since the power amplifier tube will have serious nonlinear distortion after overload, the rated output power of the amplifier is usually deliberately increased to make it greater than the rated power of the speaker . The correct connection should be: the output power of the power amplifier is 30% larger than the nominal power of the speaker. If the power of the speaker is much smaller than the power of the power amplifier, you should be extra careful when using the power amplifier. The volume should be gradually adjusted from low to high, and it should not be too large, otherwise the speaker will be damaged. In actual work, the output power of the power amplifier is relatively large, which is beneficial to improve the sound quality. In addition, the dynamic range of the sound source is very large, so we must pay great attention to the damage to the speaker caused by the instantaneous overload of the power amplifier.

The average output power refers to the power of continuous operation for a long time. Peak power refers to the maximum power it can withstand in a short period of time, which is much larger than the rated power. The output of the sound reinforcement is determined by the power amplifier. A concert of a certain scale must have a certain power, and the standard is one watt per person. Depending on the type of concert, the size of the venue, the reverberation and the number of speakers, the power will vary. Total power/output power of one power amplifier=Number of required power amplifiers Bridge output: Bridge output is a way to amplify a stereo amplifier into a single channel. It is a circuit form used to obtain large power output, also called BTL mode. The principle of the bridge connection method: use the A channel to amplify the positive half cycle signal, and use the B channel to amplify the negative half cycle signal, so that the output can double the power.

Bridge connection and specific steps: When two channels of a power amplifier work separately, the rated output power of each channel is 400W\4, which is the ordinary stereo connection. When a larger rated power output is required (below 400W), the bridge connection method can be used: 1. Turn the mode switch on the "BRIDGE" position; 2. The signal is input from the A channel; 3. The power is from the "+" of the two channels. " terminal output, the A channel is the output "+", and the B channel is the output "-".

Power amplifier output level display: The display is a trapezoidal group of colored light-emitting diodes, which is used to instantly display the level of the power amplifier. The normal level is green; when the power amplifier is required to transmit a high-pitched continuous signal, the level signal is yellow; when the audio signal peak of the music or the drum is played, the red LED is flashing (sometimes flashing). All of the above are normal phenomena. If the red LED stays on, the amplifier may be overloaded. This situation often occurs when one power amplifier drives multiple speakers. At this time, the system should be reconfigured to eliminate this overload phenomenon.

Amplifier peak display (PEAK): When the PEAK peak diode is flashing, the gain control should be lowered. Power amplifier protection display (PROTECTION): In some misoperations, the built-in protection circuit of the power amplifier will be automatically disconnected, and the protection display will flash. After the erroneous operation is eliminated, the protection display light will go out.