Your voltage and relay vibration is probably because your tiny 9V battery is severely overloaded. It is made to operate a low current smoke alarm for 1 year.

I meant to use a 9V battery but now I use a 3S 18650 cell battery, which means it is 12.6V when fully charged. When I measured the output voltage yesterday, it was 11.77V (before going through the diode, so that is why it was 11.42V above), not too low, right? When I used the voltage of the battery before going through the relay to power the whole circuit, it still worked.

 

Yes, the relay. I will check it again, but yesterday, I measured the output of the relay when I plug the jack and when without and it looked correct.

The schematic in post #67 is drawn correctly and the relay should only be activated when power is applied to J1. Looking at the numbers 1,2 and 3 marking the contacts it would appear #2 and #3 are reversed from the description of the problem.
Need to verify the contact designations are correct.
#1 = NC
#2 = NO
#3 = COM ???

 

It's ok now. It's my fault for determining the pins. Thank you guys so much!!

 

Hello sghioto and Audioguru again
I've finished the PCB layout and wiring. Here are pictures of the PCB and the schematic. I hope you guys can advise me to make sure after manufacturing, this circuit can work. If you need more information please tell me. Thank you so much!

 

Initial viewing looks OK. Appears to have plenty of ground plane.
How was the board designed?

 

How was the board designed?

Can you make it clear what you mean by saying this? I don't get it.

Appears to have plenty of ground plane.

As you said before I have to make sure the audio input signal ground to separate from the power ground, so that mean the polygon pour with net GND wasn't good, right?

 

Can you make it clear what you mean by saying this? I don't get it.

Meaning did you design the board manually or used software.
I'm no expert but I think the way it's laid out is OK.

 

Meaning did you design the board manually or used software.
I'm no expert but I think the way it's laid out is OK.

I did it manually. But how about the GND plane, can you tell me more about it?

 

Audio amplifiers are measured with a signal generator with a continuous sinewave feeding the amplifier input and an oscilloscope across the speaker to show the peak-to-peak signal across the speaker.
A VOM cannot measure normal audio frequencies and cannot measure peak voltages of music or voices.
A current meter increases the load resistance that reduces the voltage and current at the load.

Hello, if I use an oscilloscope to measure the voltage of the speaker, I will put a 1000Hz signal to the input. Then I put the two probes of the oscilloscope to the two polarity of the speaker. So then the voltage I get is what, peak-to-peak right? If not, what is it? Thank you!

 

View attachment 308598
Well, I just finished the schematic of the circuit. Is there anything should I change to make it better? Hope to get you guys advice.
I will attach the datasheet of the IC and module I use here:
DFPlayer: DFPlayer Mini Mp3 Player - DFRobot Wiki
AMS1117: AMS1117.PDF

A small but important style detail - GROUND symbols should NEVER be oriented anything but down.

 

The loudspeaker transducer itself is only half of the loudspeaker system. The speaker enclosure makes up the other half.
Mount the loudspeaker in a solid wooden box and you will hear a huge difference.

 

The speaker outputs of the TDA7297 amplifier are not grounded but one probe of most oscilloscopes is grounded and will short the TDA7297 and destroy it.

Use the oscilloscope to measure the signal with respect to ground on each speaker wire separately. With a 12V supply the average voltage will be 6VDC and swing up to +10.9V and swing down to 1.1V. Then the output into 8 ohms at 1kHz will be 6W at about 1% distortion. Its distortion will be heard at 3.4W. Corrected the voltage swing.

The rated 15W onto 8 ohms is when the supply is 16.5V and the clipping distortion is horrible at 10%.