This is a BT audio amplifier module with high and bass independent adjustment, BT + AUX audio input, dual-channel stereo output, with overheating, overcurrent, short-circuit protections mechanism. The higher the supplys voltage the higher the output power, the smaller the speaker impedance the higher the output power. Features: Adopts low noise preamp, shielded power inductor, large capacity energy storage capacitor and 3116 amplifier chip, can provide stable and quick connection, with wide compatibility. This audio amplifier module has two audio input modes: one is the BT input mode, another is the AUX input mode, BT mode priority. BT mode: no matter in which mode the BT can be connected, as long as the BT connection is successful it is the BT mode, and BT mode supports automatic back to connect. AUX mode: BT no connection when AUX is inserted is AUX mode, it should be noted that when using AUX mode, you need to confirm that the BT connection of this module has been disconnected. Main volumes adjustment function: MAIN-VOLUME knob is to adjust the main volumes, right rotation of the main volumes increases, left rotation of the main volumes decreases. The main volumes has an effect on the volumes of both the left and right channels and the subwoofer. Bass adjustment: R&L CHANNEL-BASS knob is to control the bass, right-hand rotation bass enhancement, left-hand rotation bass attenuation. When the knob is in the rightmost position, the bass is not enhanced nor attenuated. Treble adjustment: R&L CHANNEL-TREBLE knob is to control the treble, right turn treble enhancement, left turn treble decay. When the knob is in the middle position, the treble is not enhanced and not attenuated. Subwoofer volumes adjustment: SUBWOOFER-VOLUME knob is to control the volumes of the subwoofer. The volumes becomes louder with right rotation and smaller with left rotation. Subwoofer cut-off frequency adjustment: SUBWOOFER-FREQ knob is to control the subwoofer cut-off frequency. The frequency of right rotation increases and the frequency of left rotation decreases. Frequency adjustment ranges of 20Hz-200Hz. Multiple protections: over-voltage, under-voltage, overheating, direct current detection, short-circuit protections, safer to use. Specifications: Name: 50W*2 BT Audio Amplifier Module BT version: 5.0 (unobstructed, 10 meters) Input sensitivity: 500mV Input mode: AUX+BT Number of channels: 2.1 Power amplifier chip: TPA3116D2 (with AM interference suppression function) Adaptable power supplys: DC12-24V/5A or more (the higher the voltage, thehigher the output power) Applicable speakers: 20-100W, 4-8 Ohm Output power: left and right channels less than 50W; subwoofer less than 100W Protections mechanism: over-voltage, under-voltage, overheating, direct current detection, short-circuit protections Item size: 118 * 100 * 22mm / 4.65 * 3.94 * 0.87in Item weight: 195g / 6.88ounce Package size: 150 * 140 * 50mm / 5.91 * 5.51 * 1.97in Package weight: 256g / 9.03ounce Packing List: 1 * BT Audio Amplifier Module 1 * Screwdriver