Feature: 1. 3 PORTS: After the microphone and music are amplified by stereo sound preamplifier, they can be output independently or mixed output. There are three output ports in total, and the mixed output port can directly drive headphone to listen 2. INTERFACE SIZE: The 3.5mm interface of preamplifier 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 3. AMPLIFY TIMES: The 6.5mm port of the dynamic microphone is amplified by 75 times, the 3.5mm port condenser microphone is amplified by 22 times, and the stereo music input 3.5mm port port is amplified by 5 times 4. ULTRA LOW NOISE: The all aluminum housing of mic headphone amp completely insulate electrical interference, and the rail to rail OP amp MC33202 guarantee the highest sound quality at all output levels, with ultra low noise operability and excellent sound performance, which is ideal for desktop sound systems. Please use excellent quality low ripple power supply, poor power supply quality is easy to produce hum 5. WIDELY APPLICABLE: Sound mixer with two volume control knobs, which mix multiple channels into one rail and compatible with multiple devices. Suitable for musical instruments, microphones, mobile phones, computers, power amp equipment, speakers, small stage settings, drum sets or submixes, and other sound devices, with DC5‑12V power supply 5.5 x 2.1mm power hole Specification: Item Type: Stereo Sound Preamplifier Material: Aluminum alloy Color: Black Power Interface: DC5-12V, 5.5 x 2.1mm . Package List: 1 x Preamplifier