Working voltage: 3-4.5V ( if you need a higher working voltage, please add a current limiting resistor on LED, usually tens of euro to 100 euro).
Circuit principle: Sound-controlled LED melody lamp circuit consists of power supply circuit, microphone amplification circuit, LED luminous indicator circuit, power supply by JP input, C1 filter power supply circuit. MIC converts sound signals into electrical signals, which are coupled by C2 to Q2 amplification. The amplified signals are sent to Q1 base. Q1 drives LED to emit light. The louder the sound, the brighter the LED.