Car stereo amplifier

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Introduction To 18W Car Stereo Amplifier Project
This car stereo amplifier project is a class AB audio power amplifier using the Hitachi HA13118 module. It not only can be used in car application but also in any portable or home amplifier system. It is easy to construct and has a minimum of external components. The module has a high power output from a low voltage supply using the bridge tied load method, and a high gain of 55dB.
This project will be especially useful in applications where the input signal is a low level, without requiring the use of a separate pre-amplifier. This IC module has a built in surge protection circuit, thermal shut down circuit, ground fault protection circuit and power supply fault protection circuit making it extremely reliable.
The Specifications of this project are:
D.C. Input : 8 - 18V at 1-2 A

Power output : 18W maximum, 4 ohm load, 18V DC supply

S/N ratio : > 70 dB

THD : < 0.2% @ 1W

Freq. Response : ~ 30 Hz to 30 kHz, -3 dB

Input level : < 25 mV, for full output (G > 50dB)

Input Impedance : ~ 30 k ohm

The supply voltage required for this project is 8 -18V DC, at least 1 to 2 Amps. Maximum output power will only be obtained with a power supply of 18V at greater than 2 A, using a 4 ohm speaker. The power supply should be well filtered to reduce mains hum, a regulated supply will reduce noise even further. Extra filtering is unnecessary if operating from a battery supply.

Most of the circuitry is contained within the amplifier module. C10 is the input coupling capacitor and blocks DC from the input. C11 bypasses any RF which may be present at the input. C1 & C2 provide an AC ground for the inverting inputs of the IC. R1/C7 and R2/C8 provide a high frequency load for stability with difficult speakers. C5 and C6 provide "bootstrap" feedback for the IC. C9 and C12 provide power supply filtering.
An externally mounted logarithmic potentiometer of between 10k ohm and 50k ohm, is used depending on the desired input impedance. The impedance should be keep as high as possible for a guitar amp, unless using a separate pre-amp. Make surethat the heat sink is mounted to the module.