This is a kit parts. You should solder it by yourself.This circuit belongs to the OTL circuit teaching model, its maximum power is only 1W, driven by two complementary transistors S8550 and S8050.It can be used for exercise welding techniques, understanding the triode complementary OTL output type and how to adjust the static operating point, midpoint voltage, etc.. Features: High sensitivity. Low power. Wide operating voltage range. Low power consumption. DIY design. Parameters : Standby current: Less than 5mA; Soldering difficulty Level: Easy; Working voltage: DC 4V-9V(Recommend 5V); Working current: Less than 100mA; Output power: 1W(max); Output Type: Single power supply OTL; PCB Size: 65*40mm; Working principle: This circuit belongs to the OTL circuit teaching model, its maximum power is only 1W, driven by two complementary transistors S8550 and S8050; The working voltage of this kit is DC4-9V, the recommended voltage is 5V. Instructions: Step 1: Complete the installation in the normal way following installation manual and schematic.(Please request separately). Step 2: Connect DC 4-9V voltage; Step 3: Adjust potentiometers. Step 4: Test and use. Package Included: 1 xPower Amplifier Circuit DIY Kit