In order to listen to the CD (VCD) with headphones , I just installed a high-fidelity headphone amplifier with beautiful sound quality for more than 30 yuan. NE5532 is generally used as pre-amplifier, and its performance is very good. Now it is used as a low-power amplifier, what is the effect?
Looking at the circuit schematic diagram, it is almost the same as the general op amp circuit, but the resistance and capacitance of the circuit vary greatly, and the working state is different from the op amp circuit. The experiment proves that NE5532 is a small power amplifier with excellent performance. Beginner enthusiasts may wish to give it a try.
The following points should be noted during the trial production process:
1. If the power filter capacitors C9 and C10 are too small, it will cause self-excitation. When preamplifier for C9, C10 with 100μF enough, but when making the amplifier must be increased to more than 470μF. At the same time, the filter capacitor is directly related to the sound quality.
2. The resistance of R4 ( R9 ) and R5 (R10) in the circuit should be debugged repeatedly. In the pre-amplifier circuit, R4 ( R9 ) is generally 1KΩ , and R5 ( R10 ) is 100KΩ , so that its amplification factor can reach 100 times. But now as the power amplifier, there will be self-excitation, so R4 (R9) is changed to 8.2K , R5 (R10) is reduced to 33K , the amplification factor is only 4 times, the circuit will not self-excitation, and the negative feedback is also appropriate, the sound quality Soft, clear and transparent. If R5 ( R10 ) continues to be reduced to 15K , the negative feedback is too deep, not only the volume becomes lighter, but the tone is dull, the reader can repeatedly debug to achieve perfection.
3 , C2 ( C6 ) is the ground path of the input loop, only 10μF in the pre-amplifier circuit , it appears that the input impedance is too large when the power amplifier is working, the signal is blocked, causing distortion and even self-excitation. Now increase C2 ( C6 ) to 100μF , the sound quality is obviously improved, the sound range becomes wider, the treble is crisp and sweet, the midrange is pure and bright, the bass is deep and rich.
4. The power of this machine can be selected from 3V to 15V . You can use four battery strings to connect in two directions (positive and negative 3V ), the volume is not much different from 12V , but the sound quality is not as good as 12V . It is recommended to use 9V ~ 12V .
In addition, the input terminal is connected to R1 ( R6 ) 51K in series , because the volume is too loud when listening with headphones. If R1 ( R6 ) is removed, a small speaker less than 5 inches can be connected . Before the case, the bedside listening effect is also very good.
——From: Zhejiang Shen Weicheng
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The design goals of the headphone amplifier are: very beautiful sound, low power consumption, small size (3 ...