Specifications: Lithium battery capacity: 1500mAH Amp using time: about 13 hours Bluetooth decoding mode: SBC Bluetooth protocol: A2DP V1.3.1, AVRCP V1.6 ,HFP V1.7, HSP V1.2 Bluetooth distance: 8m Max Amp battery voltage: DC3.7V - 4V Amp internal working voltage: 4V SNR>100Db THD+N 0.0003% Adapted Headphone Impedance: 16-300 Dimension: 96 x 61 x 15mm(L x W x H) Package: 1 x Bluetooth Headphone Amplifier 1 x Type-C Power Cable 1 x Audio Cable 1 x Users Manual - HiFi Headphone Amplifier, It supports most headphones of high impedance 16-300, 3.5mm AUX Input and Output, signal-to-noise ratio> 100Db, THD + N = 0.0003%, fully filter noise, enjoy high-quality audio. - Bluetooth 5.0 receiver, It is designed to deliver studio-quality sound to your ears through wireless Bluetooth 5.0 technology-suitable for your existing wired headphones, earphones and even speakers. - Rechargable Lithium Battery, It adopts a rechargeable lithium battery, which allows it to stay working about 13 hours. Plus, there is a volume control knob for volume adjustment. - Two-stage Gain Switch, It enhances the signal input into the amp circuit for the optimal performance of the headphones. Make it Possibility to output not only louder sound but a sharper and more Real stereo sound without distortion - Broad Compatibility, This amplifier is remarkably compatible with a variety of digital devices, such as MP3, MP4, Mobile Phone, Computer, CD players and personal media player.