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They are arranged in a Log Scale Mode.

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better functional demonstration video in the last step I made this VU meter and video almost 3 years ago you can see that my newer youtube videos are much more refined now : But now I decided to revive the project to honour the Instructables 1000th contest! I've a 12v power supply.

J6 and J7 are used to connect a dual gang potentiometer for audio gain.

LM3914 is basically a combination of 10 comparators.

But with this simple circuit, the reading is proportional to the peak output voltage which is always very low and goes up only when the volume is really too high.

If D3 and D4 are red, the circuit may be used as a simple peak indicator, showing when the input signal exceeds a certain value.

One has to use the diode characteristic exponential function, but equations get complicated and I wasn't able to solve it with just a pencil and a piece of paper.

Even if its accuracy is lower than what is achieved with professional equipment, it's a good logarithmic approximation and is definitely good enough for a Hi-Fi amplifier of a stereo set.

This transducer is used in all mobile phones and laptops.