The board from old car power amplifier is quite nice. It is double layer board with TL494CN for the PWM control unit. It is quite common to find any car amplifier using this kind IC for the switching section. As you can see I only changes the capacitor to a better grade.
Only the power supply unit, the rest of all components has been removed.
Since the new power amplifier only require single rail power supply, then I should re-wire the transformer output wires. I will make it parallel to make it double in ampere.
It is a simple rewire from dual rail CT: 1 , 2+3 , 4 to single rail: 1+3 , 2+4.
I using another dismantled board available on my bin for the AC - DC converter.
You will rarely find the full wave DC power supply in car audio amplifier like this.
The DC out which is about 20 volt will connect to the amplifier board.
You will ask why don't I just connect the voltage input directly to the battery car by using single relay for remote on? Well, first of all, the common ground will be an ground loop issue to the head unit by using direct voltage from the car battery. Second, you will not get the full potential of this class D amplifier by only using 12 volt battery. Specification wise, 24 volt will give you about 30 clean watt per channel.
The modification to the TPA's board is only changing the SMD input capacitor to Siemens MKP capacitor. They are quite big and I have to put them outside the TPA's board. Remove C7 (+INR), C8 (-INR), C16 (+INL), and C20 (-INL). The -IN will go to audio ground.
I using the 10 K ohm potentiometer for the gain control.
Then connect them all together. The ground from TPA's board to the main board should be also connected. Mention the green one is actually a silver Teflon cable for grounding jumper.
It almost finish. New capacitor also added to replace the small one.
It is now done:)
I leave it open just like that. I forget where do I put the rest parts of the case.
This Class D car amp is an evaluation project and until now I haven't test it yet in the real car audio system. But by the result when testing on my desk, it sound very dynamic and open. So much different in sound quality compares when I only using the 12 volt input for this TPA3118 amp.
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I read your article and it was amazing! choosing the right one can make all the difference in your audio experience on the road. That's why I found this Car Amplifier Buying Guide on Technobazz incredibly helpful. It's packed with valuable insights and expert tips to help you make an informed decision.
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