Description:  The differential amplifying circuit utilizes the symmetry of the circuit parameters and the negative feedback to effectively stabilize the static operating point, and amplifies the differential mode signal to suppress the common mode signal. It is widely used in the input stage of the direct coupling circuit and the measuring circuit.     Features:  1. Support dual work module;  2. High quality sound quality;  3. Support dual output;  4. Support high temperature protection.     Specification:  1. Product Name: Differential Amplifier Board 2. Working Voltage: DC 6.0V-14.0V.  3. Output Power: 7W/10W/18W.  7W (Class D , 7.4V 4ohm ,THD=10%).  10W (Class D , 9V 4ohm ,THD=10%).  18W (Class D , 12V 4ohm ,THD=10%).  4. Amplifier level: Class D/Class AB.  5. Default Mode: Class D 6. Support Speaker Impedance: 4ohm.  7. Working Temperature range: -20°C~85°C.  8. Working Humidity range: 0%-95%RH.  9. Size: 21*21*3mm.  Set Working Mode:  The default mode is Class D.  User can use CTRL pin to set work mode.  Remove resistor R6 and R7 to change Class D to Class AB.  CTRL pin is used connect to MUTE pin from Bluetooth module.     Note:  The chip will get heat which will cause the over-temperature protection function to be activated when input voltage is higher than 12V and working in Class AB mode.     Using Steps:  1.Make sure work mode;  2. Connect the suitable speakers;  3. Connect right input voltage at input terminal;  4. Input audio signal;  5. Test and use.     Note: 1. Default Class D.  2. The chip will get heat which will cause the over-temperature protection function to be activated when input voltage is higher than 12V and working in Class AB mode.  3. Please use suitable speaker.  4. Please input audio signal.  Application:  1. DIY speaker;  2. Voice intelligent control;  3. Bluetooth signal conversion.     Package included:  1 x Differential Amplifier Board