This machine adopts attenuated tone circuit + NE5532 pre-amplification compensation, and the attenuation is -15db when it is not powered. When power is supplied, the amplifying part of NE5532 works to compensate, the gain is 0db, that is, the input and output signals are equal. Try to use low-ripple high-quality power supply for DC power supply. When the input signal amplitude is less than 1V, 12V power supply is sufficient. When the input signal is 1V, please increase the power supply voltage, the highest power supply voltage is 24V. Style: Tabletop Transducer: Dynamic Microphone Use: colour:Black Material:Metal size:88 x 52 x 38mm Package Contents: 1 x Front Audio Amplifier Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.