Features: Enhances auditory sound with the AU12C Preamplifier, featuring advanced amplification technology that delivers clear and rich stereo sound for unparalleled auditory experience. this machine with strong driving, and can easily drive all of high and low resistance headphones and auditory amplifiers! 800mAh battery, which can be used for about 8-10 hours at a time, and can drive auditory equipment such as headphones and auditory amplifiers; Choose one port as need, and cannot connect two devices at the same time; The AU12C boasts versatiled compatibility, effortlessly connecting to smartphones, computers, and tablets, making it perfectly for various scenario. Specifications: Model:AU12C Headphone Amplifier Board The front 3.5 port can drive headphones; Working frequency: 20HZ-20KHZ; Input impedance: 50K；; Output impedance: 600ω Output impedance of earphone port: 16Ω-600Ω Output power of earphone port: 500mwx2 Output voltages of OUT port: 4.9vrms/600Ω Amplification: 12 times (21.6db) Battery capacity: 800mah The light flashes continuously for 4 times to indicate 4 cells of electricity, 3 times to indicate 3 cells of electricity, and so on. The same is true when charging, and it will light up when fully charging SizE：about 9x6x2.50cm/3.54x2.36x0.98in Package Includes: 1PC AU12C Auditory Preamplifier note: The 3.5mm port and the 3pin to adapt to different situation. They cannot be used simultaneously. Just choose one of them. Due to the problem of lighting effects, there is certain tolerances in product, please understand. Please allow 0-1cm error due to the measurement.