4. Turn the power amplifier channel switch function of the rear sound field to HPF position. 5. Pre-adjust the HPF frequency of the rear sound field power amplifier to about 60-70HZ. 6. Adjust the gain of the rear sound field to the minimum. 7. Turn the channel switch of the subwoofer speaker power amplifier to the LPF position, and preset the frequency point of the LPF to about 60-70; If the subwoofer power amplifier has the function of SonicFilter (some power amplifiers only print the word Filter but have the same meaning), adjust the frequency of the filter to the lowest frequency point; If the subwoofer has a phase adjustment function, it should be preset to the position of 0. 8. Pre-adjust the gain of the subwoofer amplifier to the minimum. 9. Adjust the volume of 9. CD car stereo speaker to its maximum value of 90%-95%. 10. Turn on the power supply of the power amplifier, gradually increase the gain of the power amplifier of the front speaker, turn it to the speaker where the distortion stops, and then adjust the gain of the front sound field back a little until it is just undistorted. At this time, the level coordination between the CD host and the front sound field amplifier is basically just right. How to adjust the volume of car power amplifier Class A power amplifier is also called pure Class A power amplifier: Pure Class A power amplifier is relatively rare in the application of car audio. This is because the efficiency of pure class A power amplifier is very low, usually only 20-30%, but audio enthusiasts talk about its sound performance symptoms. Because the calorific value is amazing, in order to effectively deal with the heat dissipation problem, class A power amplifier must adopt a large radiator. Because of its low efficiency, the power supply must be able to provide enough current. Therefore, the size and weight of Class A machines are larger than those of Class AB machines, and the system is more expensive and more expensive. In most cases, the price of Class A amplifier is twice or more than that of Class B amplifier with the same power. Class A power sound is a waveform signal, so the power amplifier amplifies the sound signal, which is equivalent to increasing the amplitude of the waveform. There is no cross distortion at all, even without negative feedback, its open-loop distortion is still very low, so it is called the most ideal amplifier circuit design for sound. Class A power amplifier is an ideal choice for playing back music. It can provide very smooth sound quality, mellow and warm timbre and transparent treble, which is sought after by many audio enthusiasts. Class B power amplifier: Class B power amplifier, also called linear amplifier, but its working principle is completely different from that of pure Class A power amplifier. When a class B power amplifier is working, the positive and negative channels of the transistor are usually closed, unless there is a signal input, that is, when a positive signal comes, only the positive channel works and the negative channel is closed, so the two channels will never work at the same time, so there is no power loss at all in the part without a signal. However, when the positive and negative channels are on and off, cross distortion often occurs, which makes the sound rough. Especially at low level, so class B power amplifier is not a real high fidelity power amplifier. The average efficiency of Class B power amplifier is about 75%, and the heat generated is lower than that of Class A, allowing the use of a smaller radiator. In practical application, in fact, many early car audio amplifiers are Class B amplifiers because of their high efficiency. Class AB power amplifier: Compared with the first two types of power amplifiers, it is a design that is compatible with the advantages of Class A and Class B power amplifiers. Class AB power amplifier usually has two bias voltages, and a small amount of current passes through the output transistor when there is no signal. When the signal is small, it uses Class A working mode to obtain the best linearity, and when the signal rises to a certain level, it automatically switches to Class B working mode to obtain higher efficiency. Class AB power amplifier of ordinary machine 10W works with Class A at about 5W. Because the power used for listening to music is only a few watts, Class AB power amplifier works with Class A power amplifier most of the time, and it is only changed to Class B when there is transient strong music. This design can obtain excellent sound quality, improve efficiency and reduce heat, which is quite logical. Some Class AB power amplifiers adjust the bias current very high, so that they can work as Class A in a wider power range, making the sound close to pure Class A machines, but the heat generated is also relatively increased. Class D power amplifier: Class D power amplifier, also known as digital power amplifier, is different from the above-mentioned Class A, Class B or Class AB power amplifier. Its working principle is based on switching transistor, which can be completely turned on or off in a very short time. The two transistors will not be turned on at the same time, so little heat is generated. The efficiency of this kind of amplifier is extremely high (about 90%), which can reach 100% under ideal conditions, while the class AB amplifier can only reach 78.5%. On the other hand, the switching mode also increases the distortion of the output signal. Class D amplifier circuit is divided into three stages: input switch stage, power amplifier stage and output filter stage. Pulse width modulation (PWM) mode can be used when class D amplifier works in switch state. The audio input signal can be converted into a high-frequency switching signal by PWM, and the audio signal is compared with a high-frequency triangular wave by a comparator, and the output is low when the inverting terminal voltage is higher than the noninverting terminal voltage; When the inverting terminal voltage is lower than the noninverting terminal voltage, the output is high. Car amplifier may still have friends who are confused about this concept, and it doesn't matter. It is not enough to choose the power amplifier according to the simple parameters given in the manual. It should be based on the whole sound system, and it is necessary to listen to the opinions of other users or professionals, and choose different models and brands of power amplifiers according to different purposes. I hope that the information I shared about how to adjust the volume of car power amplifier can help my friends better understand. @20 19