This amplifier use 6J5 electronic tube and high quality NE5532, and BT4.2 version does not support APTX function. The main filter capacitor adopts 470UF / 25V, and the coupling capacitor adopts 1UF. The PCB adopts 1.6mm double-sided sheet metal, 2.0oz copper thickness, and the whole tin spraying process ensures excellent current flow efficiency. Characteristics: The use of 6J5 electronic lamp and high-quality version of NE5532 and BT4.2 does not support APTX function. The main filter capacitor adopts 470UF / 25V, and the coupling capacitor adopts 1UF. The resistor uses a high-precision chip resistor and the highest quality circuit board. The PCB board adopts 1.6mm double-sided sheet, 2.0oz copper thickness, and the whole process of spraying the tin provides excellent current flow performance. The layout of the board is reasonable, beautiful and has little current. The input and output interface are made of gold-plated RCA lotus pedestal, which is durable and beautiful. The three-knob design improves all the details, clarity, directness, richness, tone related to your music, you can easily get both strong and sweet sound. Technical data: Name: Preamplifier Material : printed circuit board Black color Power: DC12V Product size: 137 * 104 * 41mm / 5.39 * 4.09 * 1.61in Package weight: 500g/1.10lb Packing list: 1 * preamplifier