4 Channel Amplifier Parts List

D1-D4: 1N4001 (4)
C1,C20: 1000u CAP (2)
C2,C11: 47u CAP (2)
C3,C5,C7,C8,C12,C14,C16,C17,C21,C22: 0.1u CAP (10)
C4,C6,C13,C15: 10u CAP (4)
C9,C10,C18,C19: 2200u CAP (4)
R1,R4,R9,R12: 1M RESISTOR (4)
R2,R6,R10,R14: 100k RESISTOR (4)
R3,R5,R11,R13: 1k RESISTOR (4)
R7,R8,R15,R16: 2R7 RESISTOR (4)
IC1: 7812 (1)
IC2,IC3: LM1877N (2)
SPK1,SPK2,SPK3,SPK4: 8R 2 Watt speakers (4)

4 Channel Amplifier Notes

The overall gain is controlled by the ratio R14/R13 and R6/R5. Used by small Hi-Fi speakers, the volume was too loud for small room so you may reduce R14 and R6 to 33k. The Zobel network formed by R7, C7, R8, C8, R15, C16, R16, C17 prevents instability which can happen with long speaker wires. The input impedance is high, 1M and if very long input cables are present could pick up noise. Screened cable should be used, in my case I used 10k resistors between points A & C, B & C, D & F, E & F. This provides a DC path to ground and higher noise immunity. If instability does occur, then you will notice sound distortion and the LM1877N will become hot to touch.

4 Channel Amplifier circuit source: zen22142.zen.co.uk

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With the integrated audio TDA8571J designed for automotive applications, this 40w amplifier circuit can expand the sound of the car radio or connect a portable MP3 player in it. Internally, the chip has eight operational amplifier set on the bridge, allowing each speaker terminal being energized. Dont connect the negative terminal of the mass of the speaker, because they will produce a short circuit on the output.

As usual in these kinds of development, the heat dissipation is an important factor forproper cooling to ensure stable operation, but poor ventilation can destructive circuit.Although it has an internal thermal overheating protection, is still destructive.

If you want to use it at home (not recommended), you should use a 12V source capable of draining up to 250w at 12v. Remember that filtering is a key source of success in anyaudio installation. Use a large electrolytic capacitor to eliminate riple and, in turn, foreliminate the RF ceramic capacitors.

For input using shielded cable and RCA female plugs. To connect to the car radio is recommended that you put between it and the amplifier a passive equalizer, In addition to controlling the tone voice, also can reduce in signal strength.

In the audio car application should be very careful where you get power because the system requires a large amount of power. Placing it on top of the light rail is possible to damage the vehicleelectrical system or, alternatively, you can blow the fuse. A good alternative is to place itdirectly from the battery of the car and switch the power through the relay coil halogenlamps which connected in parallel to the antenna output power or control of existing equipment.

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As seen in the design, the only active component is an integrated circuit TDA7386, SGS-Thomson. It provides four channels of amplification from a 12v source. The DC input is blocked from 0.1μF capacitor. STBY mute control terminal and may or may not be implemented, is up to you. Output is symmetrical, so there is no speaker terminal is grounded (both amplified).

Cooling:
Heatsink should be enough to keep the chip in the appropriate temperature. You can use a Pentium III with a cooling fan.It is sufficient to connect to Vcc as used 12v like the amplifier.

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