Features: * Brand new and high quality * Made of high quality materials, durable * Experience enhanced audio fidelity and restore real sounds * Product performance is stable and can be upgraded for various types of bile ducts * Preamplifier frequency response 5HZ-500KHZ, as long as your ears can hear the frequency can also be heard through the preamplifier * The preamplifier has a three-level adjustable toggle switch that you can freely adjust according to your preferences and audio settings. * Wide range of applications, supports any low-level signal input. Specification: Power supply: DC12-16V Current: ≥1A 1. This line uses DC boost line power supply DC12V, which can be boosted to more than 120V for power supply; single-channel DC12V1A (DC12V1A), the current is not limited, the voltage does not exceed 16V pre-amplification; the voltage is amplified 5 times, the amplification is a bit large, and distortion is heard Can moderately reduce the volume 2. Preamp working status: full-frequency output, there is no frequency missing in full-frequency output. If you hear higher or lower frequencies, please check the preamp sensitivity of your device: the highest effective 3V without distortion! 3. The electronic tube preamplifier is in a Class A amplification state (that is, the preamplifier is always in amplification state). It is recommended to use shielded wires for signal lines, otherwise interference sound and other phenomena may occur! Instructions for use: 1. With switch positioner: Turn the knob clockwise and a "beep" sound will be heard, which is the minimum volume. Continue to turn the knob clockwise to increase the volume! 2. Lamp filament: The lamp should be inserted all the way. When you turn on the computer, you will see that the lamp filament is bright red. Note that the backlight is also red. You need a filament lamp machine to operate it. 3. Audio output input: The side close to the power connector is the output. The output should be connected to a power amplifier or active speaker, and input to the sound source: such as a mobile phone, CD, computer, TV, MP3, etc. Subwoofer level signal input 4. DC input, using DC3.5/5.5*2.1 socket 5. The left and right channel inputs are audio signal inputs and can be connected to low-level signal inputs. 6. The left and right channel outputs are audio signal outputs, which can be connected to the audio signal input of a power amplifier or active speaker. 7. Before the amplification function is available, if your sound source itself contains noise, the noise contained in the sound source will be amplified, so please use a good sound source for testing. 8. Our products have been strictly tested to ensure that the sound emitted by the machine will not be noisy until there is no problem. If you encounter the above problems, you can use testing methods to eliminate them. Package Included: 1 x preamp Note: 1.The real color of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness. 2.Please allow slight manual measurement deviation for the data.