My computer audio has been broken for almost a year. Every time I watch a movie, I use headphones. Every time I use my ears, it hurts. It’s very uncomfortable. So I want to use a small power amplifier myself. I went to the electronic market a few days ago. Found LM386, very cheap, so simply use a 386 to do a mono amplifier first, there is time to add another channel. Here to write the power amplifier design to the basic process of debugging write, commemorate this process.
1. Design We are listening to the layman, not very sensitive to the 20~20K range. Therefore, the amplitude-frequency characteristics do not need to be considered too much, but the sound that you have to use must be large, so the general output power of LM386 is definitely Not enough to pull (it seems that the ultimate power is about 1W, depending on the chip information), so it is a waste of adding a LM386 to make a BTL circuit, double the design. The circuit is designed like this, the principle is very simple, it is not said
2. Commissioning
a. The capacitance of the two 104 is originally used to block the straight, but it seems that the audio coming out of the computer motherboard and the sound card does not have a DC component, and the sound is distorted when the input level is relatively high at 104. (It is estimated to be a low frequency. Filtering sounds more pronounced when the input level is high. So remove the two 104 capacitors.
b. Power up at this time (I use 12V), pick up my MP3, um! Not bad, but the noise is more powerful, adjust the size of R1, when R1 is adjusted to the maximum The noise is gone, and the smallest time is gone. (This is not nonsense, the minimum input is gone.
The audio cable connected to the amplifier is unplugged, and there may be two capacitors on the audio cable. When the input resistor R1 is relatively small, and the LM386 self-excited to generate noise, it is impossible to zoom in. Therefore, it is decided. R1 is directly adjusted to 50K, the volume will let MP3 transfer.
c. It seems that everything is ok, get it on the computer, just pick it up, um sounds big, good!! Just thought it was going to be done, a song in the computer was finished, it should be quiet but I heard the speaker. Hey, this noise is strange. I thought it was a problem with R1. I simply removed R1 (anyway, LM386 didn't get energy from the previous stage), the noise still exists, and it is suspected that it is high frequency noise on the motherboard. At the input end and a capacitor of 102 - does not work. This capacitor does not dare to be big, it has to affect the high-frequency characteristics. It is suspected that the power is too big for C1, so it is on the power supply. 100uF capacitor, still not.......
d. At this time, grab the solder joint of my amplifier input with your hand, well! No noise, think carefully, it turns out that the line I took out from the computer is a channel and a ground, now These two are suspended and connected to the power amplifier. There is no common ground on both sides. The situation on the computer motherboard is complicated. All the sounds are awkward. So I used a capacitor of 104 to put the computer ground and the power amplifier together. Solved! The effect is very good, so the map is set like this:
3. Suggestions I recommend the LM386-N1 as the standard.
a. Power supply, unless you guarantee that your power supply is standard 12V, or you will use 9V. After all, the limit voltage is at 15V.
b. Two LM386 must be from the same batch, so the symmetry is better. If you use different manufacturers' 386 to do BTL, then wait for the buzz.
c. The gain of LM386 can actually be adjusted by adding a capacitor between the 1 and 8 feet. If the gain of the 386 is not the highest, the gain of the 386 is the biggest. So if you use the BTL circuit, you don’t need to adjust the magnification.
d. The output power of the LM386-N1 is not large, so the input range should not be too embarrassing. Although the sound is turned on at the maximum on my computer, it is still hot, so it is still appropriate (specific parameters) I have not tested it either.)
e. If the sound is relatively large, it is recommended to use more than 330uF for C1.
Calculate the price: LM386 one piece a total of two pieces, electrolytic capacitor 3 hair, ceramic capacitor 5 points, get a small piece of universal board is also less than 2, a total of 4 dollars, if you want to hear the bass Cool, spend some blood to buy a magnetic ring with a rubber band, it will be about 8 blocks. A mono amplifier is 12 blocks, the stereo is 24 blocks. The effect is absolutely not bad. But the main purpose is to play by yourself, you say Now? Give a full picture, use the mobile phone to shoot at night, the effect is not very good.....
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