After the microphone and music are amplified, they can be output independently or mixed output. There are three output ports in total, and the mixed output port can directly drive headphones to listen. The 3.5mm interface with bias can be used with electrets and common condenser microphones, and the 6.5mm interface is a dynamic microphone, which can amplify wired and wireless microphones. The 6.5 port of the dynamic microphone is amplified by 75 times, the 3.5 port condenser microphone is amplified by 22 times, and the stereo music input 3.5 port port is amplified by 5 times. The power supply is DC 5-12V, and the rail-to-rail operational amplifier MC33202 is used. Please use a high-quality low-ripple power supply, as the power supply is not good enough to easily produce hum. The power interface is DC5.5x2.1, inside + outside - not include the power supply. The input 3.5mm interface has a built-in bias voltage and can be connected to an electret microphone or a 3.5 interface condenser microphone; (What is an electret microphone? You can search for relevant knowledge on the Internet. This type of microphone is widely used in various electronic products. It is everywhere around us) The output 3.5mm interface can be connected to the microphone interface of other audio equipment or line input interfaces such as AUX and LINE. It cannot be connected to headphones for listening; Amplification gain is adjustable from 0-20db; This machine has a built-in lithium battery, capacity: 150mah. It can be charged using a mobile phone charger. It can be used continuously for more than 10 hours on a single charge. size: about 5.5 x 4 x 2.2cm Material: Metal+Plastic colour: black Package Contents: 3 x amplifier 3 x Charging Cable