Sound conditioning gas

Hehe, it seems that your knowledge of physics is not very good, just kidding.

The first switch to adjust the volume is the current amplifier. By changing the current, the volume of stereo can be adjusted. The greater the current, the greater the energy and the louder the sound.

Let's talk about the audio switch. At the same voltage, the smaller the resistance, the greater the current (I=U/R). That is to say, under the condition of constant voltage, changing the resistance can change the current, thus changing the volume.

So, you can adjust the volume by making a device that can change the size of one of the things.

How to make it: The simplest thing is to find an insulating rod (pen container, chopsticks,,,,) and then find a very thin copper wire (not covered with glue) to wrap the copper wire around the top, which should be tightly wound but not overlapped and fixed. One end is connected to one of the MP3 cables and the other end is ignored. Then, one audio cable is connected to another MP3 cable, and the other audio cable is connected to the metal ring. Put the metal ring on the coil rod and slide the ring to adjust the volume. You can choose better materials when you do it, but your device is more exquisite.

To amplify the volume on the original basis, you have to change the voltage, so you have to make a transformer.

Because your MP3 voltage is generally very low, the current will be so small that you can't feel it. Therefore, it is unrealistic to make a transformer for MP3, which requires a high voltage, and the household voltage is 220V. Therefore, if you want to change the stereo volume on MP3, you must change a stereo that can be connected to an external power supply.

This is my answer to you out of my love for physics knowledge. I hope you can learn more of these basic knowledge to facilitate your life.