High efficiency: 90% A-Class, B-Class Amplifier efficiency as only about 30% Class D Amplifier is now highly respected D-Class Amplifier efficiency is extremely high, not because of the temperature effect on the sound quality but not Add radiator and take up less space Noise reduction circuit in the Amplifier board built Power on / off without noise Application: LCD TV devices, monitors, Laptop, portable Speakers, Portable DVD players, game consoles, Phone / Handsfree Operating voltage: 2.5V to 5.5V Speaker: 4-8ohms, recommended: 4 Ohm Speaker power: 2-8W Package Contents: 4 x Amplifier Board Note: First, turn off and then Aktiv speakers or likely to cause damages to the chip; Because digital Volume control module has a large Volume, so do not be too much to leave the audio signal input signal Cut Limiter. 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. Color: Green Can using the computer USB port 5V power supply or with a mobile phone charger USB interface 5V power supply Can provide 3W (left channel) 3 W (right channel) output power at 4Ω load and 5V supply voltage conditions Module comprises a short-circuit current protection and over temperature protection Size: 21 x 18 x 3.4 mm (L x W x H) Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.