Feature: 1. Adjustable volume: turn to the right to increase the volume, turn to the left to decrease the sound weight. 2. The power amplifier board has anti-reverse protection, short-circuit protection and over-temperature protection. 3. With Bluetooth function, the effective transmission distance is 10-15 meters (without obstacles). 4. The power amplifier module is small in size, stable in performance, and suitable for a variety of installation conditions. 5. The speaker power amplifier module can be used in home or car music systems to improve audio performance. Specification: Item Type: Power Amplifier Board Material: PCB Application: Suitable for operation by college students, engineers, technicians, etc. Working Voltage: DC 5-24V Bluetooth Version: 5.0 Transmission Distance: 15 meters / 49.2ft (visible without obstruction) Number of Channels: Dual Channel (Stereo) Output Power (1KHz): 20W x 2 12V 4Ω 30W x 2 16V 4Ω 30W x 2 21V 8Ω 40W x 2 24V 8Ω Adapted Speakers (40W-200W): 4Ω (5-16V power supply) 8Ω (5-24V power supply) Module Protection Mechanism: Power supply reverse connection protection, short circuit protection, self-recovery overheating protection.. Package List: 1 x Power Amplifier Board Note: 1. When the output power exceeds 20W x 2, a heat sink needs to be installed2. The input voltage must be less than 26V, otherwise it will damage the Bluetooth power amplifier board3. The power supply voltage is relatively low but the output power is relatively large, it may produce "zizi" noise, reduce the volume or increase the power supply voltageto solve the problem