This machine is equipped with an isolated boost power supply, ensuring the purity of the signal and a wide dynamic range. Since it is an isolated power supply, it can also be used in vehicles without worrying about common ground interference. The signal processing circuit adopts the TI NE5532 operational amplifier, which is of high fidelity (HIFI) with low noise. It has left and right channel balance adjustment, volume control, and three-band equalization adjustment for high, middle and low frequencies. Mute circuit, no impact sound during startup and shutdown. Parameters: Power supply: DC5V Power consumption: 0.5W Input and output interfaces: phono jacks Frequency response: 20HZ - 20KHZ Amplification gain: 12db Equalization adjustment range: ±15db Input impedance: 50KΩ Output impedance: 600Ω Functions of knobs and interfaces: BALANCE: Adjusts the volume balance between the left and right channels. VOLUME: Adjusts the volume level. LOW, MID, HIGH are respectively for adjusting bass, midrange and treble. IN: Stereo audio input. OUT: Stereo audio output. DC5V: Power supply interface, mobile phone charging , computer USB interface, car charging, portable power supply, etc. can be used. Colour:black Material:Metal Due to different batches, the appearance and printed words slightly Package Contents: 1 * Preamplifier 1 * USB to DC Power supply cable 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.