In the future version, the adjustable resistor wiil cancelled, and the resistor is used instead of the voltage to fix the +- 12V to avoid some people's disorder. 1. Power Supply:DC9-15V 2.PT2399 Reverberation Board With Power Supply Conversion Circuit, Can Convert the Input Single DC into ± Dual Power Supply, Double the Voltage, the Dynamic range is larger, and the singing is not easy to be distorted. 3. In the karaoke pre-amplifier circuit, the power supply voltage is critical. The single 12V power supply board will be distorted and Loudly Broken, so it is still good for Dual Power Supply. 4. This circuit is Cleverly designed, the Wiring is reasonable, and the noise floor is quite low. The actual audition is no less than that of the M65831. 5. With connecting wire, potentiometer mic stand screw. 6.Dual 6.5mm dynamic microphone interface. Volume independent adjustment 7.Board size: 13.5cm*5.2cm Package 1pcs board