mp3 usb amplifier 1, pure copper transformer 2, toshiba amplifier tube made in Japan 3. with usb We are manufacturer, professional public address system. mp3 usb amplifier Description1. Bass, treble volume control2. Directly record at MP3 format3. Music sources: MP3, FM, SD card 4. 6 channels, each control one channel 5. Connect PC with USB interface, download and updated music freely 6. Play ...