... ,USB,MP3 3.Build-in Battery SE-728MP3 Portable wireless PA amplifierSpecifications:Voltage:AC 220V/110V Built-in Rechargeable Battery:12V ... 1.2AHOutput Power:20W(maximun)T.H.D.:<5%Speaker:6"Input Signal:Wire/wireless Mic, Audio(USB) Frequency Range ... , Lecture, Auction, Sale promotion, tour guide, assembly,speech,etc. Our728 series PA amplifier can let your voice get louder and sounds more ...