Fully optimized and upgraded model with added Bluetooth functionality for wireless audio enjoyment. Linear Class A stabilized power supply using imported Xiantong tubes for superior sound quality. TL431 high-precision stabilized reference ensures consistent power supply balance and constant current for operational amplifiers. All- M5 Class A stable voltage pre-stage with "0" noise for a quiet listening experience. Warm sound profile with rich mid to high frequencies and powerful low-frequency response, combining multiple advantages into one feature. After receiving the board, you only need to connect the power and signal cables to use it. The all- M5 Class A stable voltage fever pre stage has truly "0" noise, and the installation is as quiet as the deep sea. The store manager strongly recommends it to you! Use dual AC transformers or positive and negative DC power supply. AC voltage: 12V-0-12V to 15V-0-15V. DC voltage: DC ± 15V to ± 20V. Color: Black Material: PCB Package Contents: 1*M5 Class A preamplifier board Only the above package content, other products are not included. Note: Light reflection 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.