Features 【Usage Design】Power supply circuit adopts full bridge rectifier. 【Eliminate Interference】Effectively eliminate the high frequency interference of AC power grid. 【Conversion Rate】Chip has high conversion rate and strong drive ability. 【Good Performance】Better performance,noise is very small. 【Tips】Can not use 12 V battery or DC directly as power supply. Descriptio n : High quality filter power supply. The four pins of rectifier respectively in parallel connect with decoupling capacitor, which can effectively eliminate the high frequency interference of AC power grid. Two 2200UF25V electrolytic capacitor filter the negative power supply, then stabilize voltage with 7815 and 7915 double DC power supply. Now the clutter interference of power grid is very small and the voltage is quite stable. So the item has better performance.The chip has high conversion rate and strong drive ability. The frequency band is wide and noise is very small. Specifica tions : Working Voltage: AC double 15 V (10 W) Audio Input: RCA sockets Audio Output: 3P terminal Input Voltage: 3P terminal Size: 110 mm x 54 mm x 22 mm Package in cludes : 1 x Pre-amplifier Board DIY Set N ote : 1, The amplifier board can not use 12 V battery or DC directly as power supply. Power supply  should be positive and negative double DC power sources, or special AC 12 V transformer power supply. 2, This item need a power amplifier to drive speaker. 3, Please allow 1-3 mm error due to manual measurement. Thanks for your understanding. 4,  Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard. Package List