Kimdrox Mini 5V Audio Ampli Digital Amplifier Board Support USB Powered Two Channel Stereo Amp 3W+3W PAM8403 Mini Power Amplifier Board. Dimension:30 x 22 x 16mm (do not including potentiometer handle) Operating voltage: DC 2.5-5.5V Max output: 3Wx2 (5V 4) Efficiency: 90%