Digital amplifier has a higher overload capacity than analog amplifier, and it ' cause crossover distortion, transient modulation distortion and you don' have to worry about the loudspeaker internal resistance It supports Bluetooth V4.0 audio input and DC 8V to 25V voltage input Using NE5532 pre-amp, and TDA7492 chip for dual channel of 50W+50W power output Sound quality is very good by using this audio power amplifier module Applicable speaker impedance are 4, 6, 8ohm, great for turning normal speaker into Bluetooth speaker colour:Photo color Material:ABS size:8 x 5 x 2cm Package Contents: 1 x Amplifier Board Only the above package content, other products are not included. Note: Light 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.