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It is a three-channel LED color-phone based on schematic diagram NE528 – the only change made was the sensitivity potentiometer.
It is a simple ilumino-phonic system equipped with three LEDs of different colors with increased brightness, flashing to the music. Each LED represents separate frequency band (bass, medium and high). The device is suitable for use with any standard signal source (not requiring correction): casette player, CD player, tuner, etc. You can of course use any greater number of systems in a room or apartment.
Main advantages of that device are simple assembly and easy start, small size and possibility to power the color-phone by a cheap and practical plug-in power supply.
How it works:
The principle of operation can be explained by looking on the schematic diagram. Input signal (amplitude from 150mV to 1V) goes through the potentiometer PR1 controlling sensitivity, to linear amplification degree, based on the quadrant of operational amplifier LM324 (US1B). From its output, the the signal is fed to three filters: low-pass (T1), medium-pass (T3, T4) and high-pass (T6). Filter characteristic frequencies are as follows: 300Hz, 1kHz and 4kHz. The signals from their outputs go to the rectifiers (D1, D3, D5) and then to degrees which control the LEDs (US1A, US1C, US1D).
The system is powered by 15...24V. Voltage does not have to be stabilized due to the operation of all the degrees with strong feedback.
Link to original thread (useful attachment) - Iluminofonia LED by HubertFab