Hey, I wanted to ask if from my phone with a jack to jack male cable, I can go to a PCB with a amplifier and then in speaker. Because I fear that my output jack is too low to make my speakers loud.
Speaker: 8ohm 10W
Amplfiier: 8 ohm 10W

 

The headphone output can be fed to a line input on an amplifier. You will probably have to turn the volume down on the device with the headphone output because it is too high for the amplifier input. Don’t send it to a mic input on the amp, it is way too high for that.

 

The TPA3136 can be set up as a BTL amplifier where each amplifier feeds each speaker wire.
Then with a 12V power supply the output power will be about 8W with low distortion.
It will be loud if the speaker is large enough, is in in a proper enclosure and they are close to your ears.