1. Power supply: You can directly use MICRO-USB Android cable 5V for direct power supply, or you can also connect 5V power supply or 3.7V lithium battery (as shown ). Note that 5V and 3.7V power supply interfaces are different. The 5V voltage is connected to 5V and GND, and 3.7V lithium battery is connected to VBAT and GND. The maximum operating current is 5V2A. It is recommended to use a regulated 5V2A power supply for better sound quality. 2. Support USB sound card, free drive (plug and play). Connect module to computer with a USB cable, and computer can through module amplifier output. Audio output: output left and right stereo audio signals, which can be connected to two 2-8 ohm, 3-5W speakers, and 4 Euro 5W speakers. 3. This product has its own dual 5W power amplifier circuit, and must not be connected to another amplifier! The outputs of two amplifiers may not be connected in parallel or negative poles may be connected together, otherwise power amplifier chip may be damaged. 4. This product M38 is a low-power Bluetooth design solution, supports Bluetooth 4.2 transmission, 2-channel stereo lossless playback, and module can be connected to Bluetooth to quickly realize Bluetooth wireless transmission, which is very convenient. 5. In an open environment, the Bluetooth connection distance can reach 20 meters. Widely used in a of Bluetooth audio reception, a of audio DIY modification. Function Bluetooth V4.2 version, support Bluetooth automatic connection technology, support WAV/WMA/FLAC/APE/MP3 lossless decoding, stereo dual channel output. After module is powered on, the mobile phone searches for Bluetooth name -M38, and can after connecting Bluetooth. Module blue indicator light: When Bluetooth is not connected, the indicator light flashes quickly; When Bluetooth connection is on, the indicator light is always on; When Bluetooth is playing, the indicator light flashes slowly. -M38 Pin 5V----------Power positive 5V GND-------Power negative VBAT------Lithium battery anode 3.7-4.2V L-/L+ -------------Left channel output R-/R+ -------------Right channel output Colour: black Material: PC+metal Size: 45 x 20mm Package Contents: 3 x M38 Wireless Bluetooth MP3 Audio Receiver Board (For different production batches, the characters on product appearance may be different from pictures) Only above package content, other products are not included. Note: Light and different displays may cause color of item in picture a little different from real thing. The measurement allowed error is +/- 1-3cm.