An audio drive indicator, especially with a Hi-Fi installation, can be a very handy instrument to check whether there is any overload present. This circuit with three indicator LEDs in the form of a traffic light has an extremely flexible design and is suitable for a wide input voltage range.
 
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Audio level meters of all shapes and sizes have previously been published in Elektor. In this case we have conceived of something different from the usual VU meters and LED bars. Such comprehensive meters are somewhat excessive on, for example, a Hi-Fi amplifier. It is usually sufficient to have an indication to show whether and output signal is present, how much headroom there is and whether the amplifier is being overdriven. All this requires only two or three LEDs. In this case the indicator comprises three LEDs in a kind of traffic light design. These indicate the following.