Sound Indicator presentation for Science Class

In the era of tube radio, the way to monitor sound signal is owed by Magic-Eye or Neon bulb. Today some may wonder how it was going for the method was too simple to indicate only showing with the light strength. Thus I designed a simple LED Audio Indicator to show how it works in science class.

The circuit is very simple. I used 2 Complimentary TRs, 2SA949 and 2SC2229, for the voltage amplifier and driving the 35 LEDs. Both can work DC150V max. so it's very bright in proportion to the sound input but the power consumption is only 2W or around.

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