Features: 100% brand new and high quality Please disconnect the bluetooth-compatible connection when using. Audio input attention: This power amplifier has an energy-saving mute mode, please pay attention to the following use, otherwise it will cause no sound output.Use bluetooth-compatible or RCA INPUT, and the volume input should not be too low, otherwise it will be muted after 1 minute. It is recommended that the volume of the external audio source is not less than 60%. Power-on precautions: Plug the 24V adapter into the power supply, and plug the DC head into the product after the adapter light is on. Do not use other power sources for testing, which will damage the product. If the adapter light does not light, please do not connect it to this product. Damage the machine. Before use, make sure that the switch is OFF and the main volume is not at the maximum position. Connect all the cables, connect the antenna, and connect the power supply. Turn the switch to ON again. At this time, the LED lights up. Start normal use. This product only supports 24V DC power supply, using other power supplies may cause abnormalities.BASS OR Treble can only be fine-tuned .The frequency response at the maximum right twist is the original value. Package Includes: 1 x Bluetooth-compatible Audio Amplifier 1 x High-quality Power Supply 1 x AC Power Cord 1 x User Manual 1 x Bluetooth-compatible Antenna (Notice: The bluetooth-compatible antenna is placed in package slot, please check carefully.) Specifications: Output Power 4R@100W(50W+50W) Terminating Impedance: 4Ohm - 8Ohm THD THD