Description: 1. Using original 6J5 tube, original NE5532 2. The main filter capacitor uses the original 470UF/25V, and the coupling capacitor uses the imported capacitor 1UF. 3. The resistor uses high-precision chip resistor to ensure 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 ensure good passing performance of large and small currents. First-class PCB quality. 5. The input and output are made of gold-plated RCA lotus seat, which is durable and beautiful! 6. The board layout is reasonable, beautiful, and the current is small. Specification: Power supply: DC12V 1A-2A ( 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 Bluetooth : 5.0 Package Includes: 1x 6J5 Tube Preamplifier Note: 1. This finished machine is a preamplifier, 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, burnt if the voltage is unstable. It doesn't support phonograph connection, it can't work to connect to the phonograph and may also damage our products. 2. The probability that the normal audio 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.