Usage Tips:Stable performance: with better noise performance, excellent output drive capability and relatively high small signal bandwidth, large power supply voltage range. Protection mechanism: overvoltage, undervoltage, overheating, DC detection, short circuit protection hint: When the audio input is enough and the power supply voltage/current is enough, there will be enough output power The higher the power supply voltage, the greater the output power, the smaller the speaker impedance, the greater the output power Please make sure that the power of the adapter power is greater than the actual working power of the amplifier Wide range of uses: suitable for high quality and professional audio equipment, inst ents, control circuits and telephone channel amplifiers. It has the characteristics of small size, high efficiency, high power and small heat. Model: ZK-TB21 Bluetooth Version: 5.0(no shielding, 10m) Input sensitivity: 500mV Audio Input AUX+Bluetooth Channel: 2.1 Chip: TPA3116D2(with AM anti-interference function) Power: DC12-24V 5A Adapter speaker: 20-100W, 4-8ohm Output power: Max.50W(R and L channel), Max.100W(subwoofer) Protection Mechanism overvoltage , undervoltage, overhearing, DC detection, short circuit protection Material: PC+Metal colour: Black Package Contents: 1 x Digital Amplifier Module 1 x Screwdriver 1 x Power Adapter Only the above package content, other products are not included. Note: Light reflection 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.