How to Boost LM386 Audio Amplifier Output Using TIP147 and TIP142 Transistors?

The discussion addresses improving the output of an LM386 audio amplifier when used with a microphone, focusing on integrating power transistors like TIP147 and TIP142 or Darlington pairs for higher amplification. Key advice includes adding a preamplifier stage to boost the microphone signal before feeding it into the LM386 amplifier, as the mic signal alone is too weak. Suggested components for the preamp include 2N3904 transistors and proper biasing with resistors (e.g., adjusting from 82k to 68k) and coupling capacitors (2.2 µF) to prevent DC distortion. Users reported issues with distortion and overheating of TIP31 transistors when using higher supply voltages or currents, recommending lowering supply voltage to around 15V, adding series resistors (4.7 Ω, 10W), and using heat sinks. Proper biasing and component values (e.g., R9, R10 resistors) are critical for stable operation. The discussion also highlights the difference between mic-level signals (50-60 mV) and line-level signals, emphasizing the need for a preamp for microphone input. Attempts to increase output power to about 25 watts require careful transistor selection and thermal management. Additional suggestions include using a 47k preset resistor for volume control to reduce distortion and ensuring the electret microphone body is grounded. The conversation also touches on troubleshooting intermittent operation related to the 2N3904 transistor and requests for sound-reactive LED circuits compatible with the amplifier setup.
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