Determine whether the noise is caused by common ground: 1. Connect the headset to the car MP3 and AUX (3.5mm interface) of the car navigation. If the sound heard from the headset is no noise at this time, you can confirm that the noise of the car equipment is caused by the common ground. 2. Use an audio cable to connect a battery-powered mobile phone or MP3 (note that the mobile phone and MP3 should not be connected to any power source in the car, such as a telephone), and the AUX of the car center console, and play the music of the mobile phone, so there is no noise , It can be confirmed that the previous noise caused by the common ground. 3. Computer, power amplifier, audio, CD: Use passive headphones to plug in the computer to try to hear whether there is noise, use mobile phone to plug in the power amplifier and audio to audition, if there is no noise in the separate audition, it is basically judged that it is caused by common ground. 4. After starting the car, the installed power amplifier has current noise, and some models will also have the situation that the greater the throttle, the louder the current noise, this product can solve this problem. 5. There is current sound between the power amplifier and the speaker or audio, you can install this product between the power amplifier and the speaker. 6. When the notebook computer is connected to the projector and the power amplifier is connected to the power amplifier, there will be noise. You can connect the adapter power supply or use the battery through the notebook. Add a common ground isolator to eliminate noise. Parts selection: Two audio are used. The transformer materials are made of high-quality materials, which have high sensitivity and high reducibility, and the sound is fuller and purer than similar. Circuit design: Stereo dual-channel independent design, very suitable for small spaces and other car interior installation. Main function: Eliminate current sound, common ground isolation audio transformer eliminates current sound caused by AUX common ground, output and output ground wires are isolated by transformer, not common ground. To put it simply, common ground means that the grounding points of two electrical appliances are not at the same point. Due to the difference in grounding resistance, noise is transmitted into the electrical equipment through the ground wire, causing interference. Because the ground points of the two devices are different, common ground noise may be generated. In the car audio, there is a kind of audio interference, like a whistle sound, the frequency of this noise will change with the engine speed. Therefore, this product can only eliminate the noise and current sound caused by the common electricity and common ground products, but cannot eliminate the noise caused by other reasons, so you need to personally confirm the noise source. Colour: green Material: PCB Size: 50 x 40mm Package Contents: 1 x Audio Lsolation Transformer Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.