How to connect power amplifier and speakers?
The output impedance of the power amplifier and the input impedance of big bluetooth speaker have different meanings. Is it as good as possible or is it better to choose a big bluetooth speaker with a small impedance? And so on. Therefore, understanding the connection between the power amplifier and big bluetooth speaker is a must for a good power amplifier.
1. Power matching According to our general understanding, it is the most reasonable and safest that the power of the power amplifier is equal to that of big bluetooth speaker, but it is not. Due to the definition and test of the output power of the power amplifier, the average rated power of the sine wave is used, and most of big bluetooth speakers work in the state of amplifying the audio signal, that is, the non-sine wave state. Considering that the audio signal is replaced by pink noise, and The peak level of the pink noise signal is 6 times greater than the average value of the sine wave signal, and to ensure that the peak signal is fully amplified (without clipping), that is, the output power of the power amplifier must be 6 times the power of big bluetooth speaker. Of course, this is More extravagant, general big bluetooth speakers will not work in the rated power state. We can choose 2 times, but not less than the power of big bluetooth speaker.
You may ask, why can’t the output of the power amplifier be less than the power of big bluetooth speaker? Isn’t it safer for big bluetooth speaker to have a smaller power amplifier? The conclusion is just the opposite. We know that the rated output power of the power amplifier is the maximum undistorted power (the degree of distortion is constant). When we increase the intensity of the input signal, the output signal of the power amplifier will also increase, but at this time, the degree of distortion increases rapidly. From the working state of the power amplifier tube, it is in a saturated state, and from the analysis of the waveform, it has produced wave-suppression distortion. That is, when the input is a sine wave, the output is a waveform close to a square wave. Further theoretical analysis shows that such a waveform expands according to the Fourier series, and there are a large number of high-frequency harmonics. Therefore, it will have a great impact on the treble head of big bluetooth speaker, and most of them will burn the voice coil.
2. The frequency matches the current power amplifier, and its frequency response can easily reach 20~20K, but most of the general big bluetooth speakers can only reach 80~16K, and seldom can reach 20~20K. Therefore, we work in the system At the same time, it should not and is not necessary to work the frequency response of the power amplifier at 20~20K, but use peripheral equipment to perform low-cut or high-cut to adapt to the frequency bandwidth of big bluetooth speaker and make the sound more pleasant.
3. Impedance matching Power amplifiers and big bluetooth speakers have their own nominal impedance values, as mentioned above. The smaller the impedance of big bluetooth speaker, the greater the output power of the power amplifier, but at this time it has a greater impact on the power amplifier, mainly the output power and stability. The output power of the power amplifier increases, which means that the current flowing through the power amplifier tube increases. At this time, the temperature of the power amplifier tube will rise, and the reliability of the power amplifier tube will decrease; on the other hand, due to the internal resistance and line resistance of the power amplifier The existence of big bluetooth speaker impedance decreases, and the relative line loss increases, which directly leads to the reduction of the power obtained by big bluetooth speaker, resulting in a decrease in efficiency. Therefore, the impedance of the two is required to match. - A big bluetooth speaker with 89 or 40 is more suitable, and it is not appropriate if it is too large or too small. (Especially when multiple big bluetooth speakers are connected in series or in parallel).
4. The connection between the power amplifier and big bluetooth speaker. The so-called connection mainly includes three aspects:
One is the phase problem. Generally, power amplifiers and big bluetooth speakers use red and black binding posts to indicate their polarity (that is, phase). Generally, in the use of a single big bluetooth speaker, we don’t need to consider the phase. In dual-channel (two big bluetooth speakers work) When the distance between the two big bluetooth speakers is more than 6~8 meters, we don’t need to consider the phase, because the correlation between the two big bluetooth speakers is not very great. We only consider the phase problem when multiple big bluetooth speakers are used in combination and stacked together. That is, the phases must be consistent.
The second is what form the power amplifier output takes.
The third is the wire diameter of big bluetooth speaker wire. This problem is very important when big bluetooth speaker wire is relatively long, more than 10 meters, especially when it is 30 to 50 meters. Therefore, it is required to choose a big bluetooth speaker wire with a thick wire diameter and a good material. Cheap, resulting in increased line loss and a decrease in damping coefficient.
