The quad amplifier 40W circuits has a 4 speaker output with their foreign 4 ohm impedance. This amplifier works with a voltage of + 12VDC so it will be suitable for use in car audio systems.
This amplifier circuit has a level of harmonic distortion as much as 10% at full strength, but when the circuit set at half power (20W), the levels of harmonic distortion generated 2% only.
TDA8571J IC is already integrated and designed for car audio purposes. The input of this amplifier can be connected of MP3 player, radio, and CD player. Because it is based IC, this circuit is very practical and requires only a few passive components to be able to work fully.
In each set of IC-based amplifiers, heat dissipation is quite important to note, therefore, use a heatsink on Fuad 40W amplifier to prevent overheating that can cause damage to the circuit.
The power supply also affects the quality of the audio quality produced. Use a power supply that is already well-regulated.