Feature:1. TPA3255 HIFI Chip: ZK AS21 amplifier board adopts two TPA3255 amplifier chips. It supports 1638V wide voltage input, maximum power 220Wx2 plus 350W (PMPO).2. Treble And Bass Controls: Bluetooth amplifier board is designed with high frequency and low frequency knobs for easy control, making the sound more layered and the bass more powerful.3. High Compatibility: DC adapter (plug size 5.5mmx2.1mm) on the market can basically meet the demand. If you don't have a DC plug, you can also connect the positive and negative poles of the cord directly to the power socket of the amplifier board.4. Guard Function: The Bluetooth power amplifier board has various guard mechanisms including short circuit, under voltage, over voltage and clipping guard to ensure its safe operation.5. Other Functions: This sound power amplifier module also supports APP control, you can modify the Bluetooth name, set the Bluetooth password, and turn off the prompt sound.Specification:Item Type: BT Amplifier BoardMaterial: PCB, Aluminum AlloyBT: 5.1Supply Voltage: 16-38VSupport: BT, AUX, USBNumber of Channels: Left and Right Dual ChannelOutput Power: 220W x 2 Plus 350WSpecial Functions: Support APP Control, Modify BT Name, Set BT Password, Turn Off Prompt SoundGuard Mechanism: Over Voltage, Under Voltage, Overheating, Short Circuit, Anti Reverse Connection.Package List:1 x BT Amplifier Board2 x Shell 13 x Screw4 x Stud5 x Knob 1 x Screwdriver