... used to make it produce powerful and deep bass Analog amplifier, bass and treble clarity, built-in lithium battery, MICRO SD ... playback.Play music,with high-powered loudspeakers,long time playWith line in function,can switch-in Notebook PC,MP3,MP4,Ipnone ... :USB charge:7 hours USB(5V/1A);AC transform charge:4 hours(optional)Storage Capacities:1GB,2GB,4GB,8GBIterface Transport:USB2 ...