Steps:

1. Some parts we need in this project.

2. The main steps to make the circuit.

3. Connect it to speaker and cellphone then test it.

Product list:

D718 transistor  https://www.utsource.net/sch/D718

1000uf 25v capacitor  https://www.utsource.net/sch/1000uf%2025v%20capacitor

4700uf 25v capacitor  https://www.utsource.net/sch/4700uf%2025v%20capacitor

680ohm resistor   https://www.utsource.net/sch/680ohm

474pf 100v

500k volume

More details, pls check the video on Youtube: