Instructions for use Use scenario: 4 people listen at the same time, two playback devices, 4 people can freely control the volume 2 in 4 channel out stereo headphone amplifier is a 2 channel mixer with 4 high-power stereo amplifiers, each channel output level control, each channel can independently control the volume, the minimum volume can be regarded as closed, 3.5MM headphones and Or 6.35MM headset (requires a 3.5MM to 6.35MM adapter). Compact Design6.7 in*2 in*1.26 in, Weight: 7.8 oz Good SoundContains 4 independent stereo high-power 5x amplifiers (14db), which can maintain the highest sound quality even at maximum volume. Adopt NJM4556A low voltage high current dual op amp, ultra low noise op amp for excellent audio performance: same as op amp in large size audio equipment AccessoriesEquipped with 12v 1a power adapter