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Stereo Spectrograph


Most stereo systems have some kind of music level indicator, The indicator may be as sim pie as a set of LEDs, ordinary low-voltage lamps or V-U (volume-unit) meters. These were later replaced by bar-graph type LED indicators. Though attractive, they provide only one-dimensional ‘movement’ of LEDs with the music. Now this system has also become very common.

Presented here is a spectacular system to replace the outdated music level indicators. This system is capable of providing a smart, two-dimensional ‘dancing’ effect on a square matrix of 100 LEDs.


In this system, out of 100 LEDs arranged in a square matrix, only one LED glows at a time and it keeps dancing within the so-formed LED array along with the music being played or the stereo system. The movement or dancing of the LED depends basically on the ‘stereo’ effect of the music Hence, the system may be called s stereo spectrograph.

This system ’s working depends not only on the type of music being played but also on the ‘stereo’ effects of the music. Greater the stereo effect, hater the movement of the dancing LED. As you know, a stereo signal is recorded or played on two independent channels which arc purposely isolated from each other. Therefore, at every instance the signal strengths of the right and left channels are different from each other. As shown in the schematic block diagram (Fig. 1).

The audio signals from the left channel are made to force the glowing LED to move along the vertical columns and the signals from the right channel provide the movement of the LED along the horizontal rows. Hence, we see ‘movement’ of the glowing LED in a two-dimensional square area where t he vertical and horizontal movements are isolated from each other* just like audio signals in both the channels.

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