1、The volume is adjustable, turn the adjustment button to the right to increase the volume, turn the adjustment button to the left to decrease the volume. 2、With anti-reverse protection, short-circuit protection and over-temperature protection. 3、With Bluetooth 0 version, the effective transmission distance is 10‑15 meters/38‑49.2 feet. 4、Suitable for various installation conditions, better audio performance, suitable for your home or car music system. 5、Wide range of applications and is suitable for operation by college students, engineers and technicians. 1 x Power Amplifier Module Item Type: Power Amplifier Module Material: PCBPurpose: Suitable for operation by college students, engineers, technicians, etc.Working Voltage: DC 8~24VBluetooth Version: 5.0Transmission Distance: Approx. 10 ~ 15meter / 32.8 ~ 49.2ft (visible without obstruction)Number of Channels: Dual channel (stereo)Output Power (at 1KHz): 2 x 16W at 12V 4Ω2 x 10W at 12V 8Ω2 x 15W at 16V 8Ω2 x 20W at 20V 8Ω2 x 30W at 24V 8Ω (heat sink required)Adapted Speakers (30W~150W): 4Ω (8~12V power supply)8Ω (8~24V power supply)16Ω (8~24V power supply)Module Protection Mechanism: Power supply reverse connection protection, short circuit protection, self-recovery overheating protection.