HAOYI The potentiometer adjusts the volume with a switch for easy control of the volume, making it Perfect for DIY speakers.If it is a metal box, you need to bring out the Bluetooth antenna.The copper DC connector is used to withstand high current and no heat.Capacitor 470uf35V solid capacitors storage and heat dissipation, and stable supply is a prerequisite for good sound quality.Free DC head lead, compatible with the input interface of this product, even if you don't have a DC head adapter or battery, it can be easily wired.5.0 Bluetooth version, the transmission efficiency is higher, the transmission distance is farther.Precautions for use: The switch on the board is the standby switch. After the switch is turned off, the machine is in a low- standby state. To completely turn off the or unplug the DC plug on the machine for a long time.Question and answer:1. How to choose a supply?The supply with the board is critical. The higher the voltage, the higher the current and the better the output . If you only have 12V 1A, you can bring a 3-4 inch speaker. If you are 19V 5A or above, there is no problem with 8-10 inches, and the supply must be highly valued. If the voltage is too low, the sound will be distorted after the sound is amplified. If the current is too small, the speaker will pull the voltage low, work abnormally or the sound quality will deteriorate.It is recommended to use 18V19V24V supply with current above 3A. If you only have 9V12V or 1A 2A supply, it can also be used but the is small. Please pay attention to the maximum volume when using it, which may affect the sound quality.2. How to choose a speaker?Commonly used speakers are generally 8 ohms, can not distinguish between positive and negative, the effect is e same, 4 ohm speakers can also be used.Colour:blackMaterial:plasticSize:55*38*17mmPackage Contents:1 * amplifier board(with DC cable)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.