1. Using 6J5 tube, NE5532 2. The capacitor uses the 470UF/25V, and the coupling capacitor uses the capacitor 1UF. 3. The resistor uses high-precision chip resistor to a good signal-to-noise ratio of the whole machine. 4. PCB adopts 1.6mm thick double-sided sheet, 2.0 oz copper thickness, and tin-spraying process to good passing performance of large and small currents. First-class PCB quality. 5. The input and output are made of gold-plated lotus seat, which is and beautiful! The board layout is reasonable, beautiful, and the current is small. Basic parameters: Power supply: DC12V2A ( needs to be regulated by 12V, not higher than 12V) Machine size: about 129* 100* 35MM (without tube height) Panel function: switch treble adjustment bass adjustment total volume Note: 1. This finished machine is a preamplifier, not an amplifier. It should be used with a post-amplifier or an active speaker. It is not allowed to directly connect passive speakers, speakers and earphones to the power amplifier; if it is not used, the car be burnt if the voltage is unstable. 2. The probability that the normal audio line or power supply is not good enough to cause the noise at the bottom noise is very high. It is recommended to use a good audio cable or power supply. 3. Make sure that there is no problem with your source. The preamplifier itself has a preamplifier function. If itself is noisy, then the preamplifier only amplify its noise. Please use a good source test. 4. Check if the tube is plugged into the base. Please insert the tube and the base. Be sure to insert the tube in case of power failure. Note: Power supply is not included in the package. You need to buy 12V2A power supply by yourself. Material:Aluminum alloy colour:black Package Contents: 1 * 6J5 Tube Preamplifier Only the above package content, other products are not included. Note: Light 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.