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This is the simplest amplifier works on the principle of band pass filter and no external power supply is needed.

In previous tutorial I made a TDA2030 stereo based 28w amplifier. which is operated by external power supply. but how to use an amplifier without improper signal strength and frequency. That’s why preamplifiers come into market. Because I did not want more regulators/ wires and power supplies here in this circuit, I am making a preamplifier which runs without any power supply. here one thing may come in your mind, how we can change the signal specifications without powering the circuit. And that is possible due to band pass RC filters.

1) 47k potentiometers
2) 4.7k and 560R resistors
3) 47uf capacitors
4) 471 and 103 ceramic film capacitors
5) Custom PCB from JLCPCB

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