Item Type: Amplifier Material: Aluminum Alloy Battery: Lithium Ion Battery 502030 (Built In) Battery Capacity: 350mAh Power Supply: DC 5V Interface: 3.5mm Tuning Frequency: 300HZ to 4KHZ Practical Use: Direct Drive Headphones to Listen, Can Be Connected to Cell Phone Recording Product Size: Approx. 108x42x42mm/4.3x1.7x1.7in Package List 1 x Amplifier 1 x Power Cord 1 x Headphone Cable Manual measurement, please allow 1& 8209;2mm error. 1CLEAR SOUND: Headphone amplifier high sensitivity, ALC automatic level control, 1000 times to amplify your voice, so you can hear the faint sound. The sound is clear, crisp, noise free and distortion free. 2WITH FILTER: Sound power amplifier with filter, the listening frequency control between 300HZ to 4KHZ, the environment in the low frequency rumble high frequency noise filtered out, retaining the human ear often hear the frequency components. 3HEADPHONE INTERFACE: Stereo sound amplifier direct drive headphones to listen, can be connected to cell phone recording, the interface is 3.5mm. through the output into their own headphones, HiFi private listening. 4ALUMINUM ALLOY: Stereo speaker amplifier with premium aluminum alloy shell, 108x42x42mm compact size, storage and carrying are very convenient, beautiful appearance, fashionable and powerful. 5APPLICABLE SCENARIOS: Power amplifier ensures lossless signal and strong anti interference performance, very reliable. Suitable for teaching, trainer, singer, coach, shopping mall, presentation, outdoor speech, etc.