1.Aluminum high density heat-sink with easy installation design. 2.Low noise operational amplifier-based audio tone adjusting circuit 3.Straight-through front amplifier circuit, external analog audio input and Bluetooth can use at the same time.The external analog signal directly enters the front without passing through the Bluetooth chip Grade amplification, good sound quality. 4.Adjustable Gain and Crossover frequency bass Sallen-Key filter design. 5.The solid inductor output LC filter filters out high frequency switching noise interference brought by switching high frequency interferences. Adjustable Treble and mid-bass level of left and right channels. Virtual Surround function based on pure analog circuits. Adjusting surround knob to middle to disable this function. Input DC Voltage: 8-26V DC, 3A or more Input analog signal level: 1V rms. Output Power:L+R 50Wx2 4ohm 24VDC +Subwoofer 100W 2ohm 24 VDC Subwoofer Crossover Frequency: Adjustable: 40Hz - 160Hz-3dB Bluetooth Connection Type: BT v2.1 EDR (Classic Bluetooth for audio) A2DP SBC 44.1kHz 16bits + AVRCP and BLE v4.2 HID (Bluetooth Low Energy, not for audio) Internal Antenna,IPEX Gen1 External Antenna Supported MP3 Supported Files Types: MP3,AAC, WAV. DAC Digital to Analog Converter: 2ch 44.1kHz 16bits. Support speaker impedance:4ohm-8ohm,Bass channel 2ohm-8ohm Color: As Shown Material: Electronic Component Package Contents: 1 x Bluetooth digital amplifier board