Build Your Own Car Stereo

lorant

Build Your Own Car Stereo [Copy link]

The car stereo introduced in this article is relatively simple, and the ICs and related components used are also easy to purchase. It consists of a preamplifier, FM radio, audio amplifier, and power supply.

Figure 1 shows the circuit of the power supply, preamplifier, and FM radio. CON1 is used to connect the output from the FM radio. The FM radio consists of a single-chip FM receiver front end (such as Sony CXA1019S or Philips TEA5591) plus an FM stereo decoding chip (such as TEA1330 or TEA7343). This FM radio board can also be purchased directly from the market or installed by yourself.
LA3161 (IC3) is easily available on the market, and its signal-to-noise ratio is very good. Be careful when soldering LA3161 to the printed circuit board, and try to avoid overheating the soldering iron on the lead corners. Use metal clips to clamp the pins for temporary heat dissipation during soldering.

If you can't buy LA3161, you can use LA3160, M5152L or KA6625S instead, but KA6625S is a 9-pin chip, and the 9th pin can be bent and not connected.
The 12V power supply comes from the car battery, and the battery terminal is directly connected to the CON2 connector. The ripple component in the battery voltage can be filtered out by C14~C16 (each 4700μF), and the filtered 12V is directly sent to the power amplifier part as the power amplifier power supply; the other part is sent out as +5V after the voltage regulator chip 7805 for the preamplifier circuit and FM radio part. To avoid noise and hum caused by ground loops, the resistance between the preamplifier ground and the power amplifier ground should not exceed 3Ω.

Figure 2 is the power amplifier circuit, which uses two LA4440s widely used in the audio field. When configured as dual-channel, the output of each channel is 6W, and the power is increased to 19W when the two outputs are connected as a bridge output.
The recommended power supply voltage for this IC is 13.2V, and the speaker impedance is 4~8Ω when used for bridge connection. In addition to its own heat sink, LA4440 also requires an additional heat sink to prevent IC overheating and thermal collapse. The ripple-free power supply is connected to pin ⑾, and pins ③, ⑥, ⑧ and ⒁ should be grounded to avoid introducing noise. Pins

② and ⑥ are input signal pins. When used in bridge connection, one of the two pins is connected to the signal and the other is grounded. In the figure, pin ② is connected to the signal and pin ⑥ is grounded; pin ⑥ can also be used to connect the signal and pin ② is grounded. IC pins ⑩ and ⑿ drive two high and low-pitched speakers in a bridge connection. Pins ⑩ and ⑿ are also connected to RC circuits to prevent steamboat noise at the output end. Pins ⑤ and ⑦ are grounded through capacitors and RC networks respectively. Pins 9 and ⒀ are bootstrap pins, connected to pins ⑩ and ⑿ respectively through bootstrap capacitors.

The audio signal sent from the preamplifier or FM radio is amplified by the power amplifier and then drives the high and low frequency speakers through the frequency division circuit. The typical voltage gain of LA4440 is 51.5dB. The volume control is done in analog mode by VR1 and VR2 in Figure 1.

The IC chip itself must have sufficient heat protection measures to dissipate the heat released by the chip when it is working, and also leave enough heat to deal with the heat released by the car engine. Figure 3 is a diagram of the printed circuit board circuit and component distribution.
The sound source is the headphone output of a pocket radio or CD player drive. When connected, use a potentiometer as a volume control and then connect it to the preamplifier. Adjust the potentiometer to make the output appropriate. If it is normal, a loud sound can be heard in the speaker. However, the sound may be slightly distorted at this time. If the sound is abnormal or there is no sound at all, you can eliminate it one by one according to the attached table.

After all circuit faults are eliminated, the audio circuit can be adjusted and optimized.

1. Install the entire system together with the tape cassette mechanism, volume control and all required external components into the audio box, and connect the audio playback head to the preamplifier.

2. The power supply of the cassette motor must be provided by a battery. In order to eliminate the reverse electromotive force of the motor coil, a rectifier diode D1 can be reversely connected across both ends of the motor.

3. The antenna of the FM receiver must not be in direct contact with the metal part of the car and should be insulated. Usually a retractable whip antenna is used.

4. The method of connecting the FM receiver kit to the circuit board is as follows: connect the power supply line of the FM radio to the +5V terminal and ground terminal of the 7805 via CON3; connect the audio output of the FM component directly to the power amplifier (via CON1) instead of through the preamplifier.

5. Adjust other circuits first, then adjust the FM receiver component. Usually two adjustments are made: one is to adjust the preset potentiometer placed near the single/dual channel converter chip (TA7343A, KA6225S, TEA1331, KIA6224A, etc.). When the FM stereo indicator LED lights up, the component can provide FM stereo; the second is to adjust the fine-tuning capacitor of the FM radio part to make the received FM station sound the clearest.

Finally, pay attention to the power supply voltage of the FM radio not to exceed 9V.

yangtao0618

zhjzh72_2004

Make your own car stereo...................... zhichi

闫平

Very good, because it is very careful. Not only does it explain the principles clearly, but it also includes an appendix on troubleshooting.

luowei01051145

I still don’t quite understand it yet!