1、Using 6J5 electronic tube and fine-quality NE5532, and BT4.2 version do not support APTX function. 2、The main filter capacitor adopts 470UF/25V, and the coupling capacitor adopts 1UF capacitor. 3、The resistor uses a high precise chip resistor, and first-class printed circuit board quality. 4、The printed circuit board adopts 1.6mm thickness double-sided sheet, 2.0ounce copper thickness, and the whole process of tin-spraying ensures the fine passing performance of the current. 5、The layout of board is reasonable, beautiful, and with small current noise. 6、The input and output interface are made of gold-plated lotus pedestal, which is long lasting and beautiful. 7、Three knobs design improves everything detail, transparency, immediacy, richness, you can get both powerful or sweet sound easily. This amplifier adopts 6J5 electronic tube and fine-quality NE5532, and BT4.2 version do not support APTX function. The main filter capacitor adopts 470UF/25V, and the coupling capacitor adopts 1UF capacitor. The PCB adopts 1.6mm thickness double-sided sheet, 2.0ounce copper thickness, and the whole process of tin-spraying ensures the fine passing performance of the current. Features: Using 6J5 electronic tube and fine-quality NE5532, and BT4.2 version do not support APTX function. The main filter capacitor adopts 470UF/25V, and the coupling capacitor adopts 1UF capacitor. The resistor uses a high precise chip resistor, and first-class printed circuit board quality. The printed circuit board adopts 1.6mm thickness double-sided sheet, 2.0ounce copper thickness, and the whole process of tin-spraying ensures the fine passing performance of the current. The layout of board is reasonable, beautiful, and with small current noise. The input and output interface are made of gold-plated lotus pedestal, which is long lasting and beautiful. Three knobs design improves everything detail, transparency, immediacy, richness, you can get both powerful or sweet sound easily. Specifications: Name: Preamp Material: printed circuit board Color: black, silver (optional) Power supplys: DC12V Item size: 137 * 104 * 41mm / 5.39 * 4.09 * 1.61in Package size: 250 * 200 * 70mm / 9.84 * 7.87 * 2.76in Package weight: 500g / 1.10lb Packing List: 1 * Preamp 1 * Preamp