VU (Voltage Unit) meters are often included in analog audio equipments to display a signal level in Visual Units. We are building a mono input VU meter in this project. You can build one pair to use them in stereo mode.
Structure: Input sensitivity is about 1 Volt rms, up to +6dB. You can adjust the input amplitude by using the multiturn 50k linear potentiometer (POT1). Circuit needs symmetric ±12V power supply because of the LM324 opamp. We used metal film resistors (1% Tolerance) so accuracy is sufficiently high. Visual duration can be adjusted by using linear 10k potentiometer (POT2). LEDs should be 5mm x 5mm in size for best fit. But we used standard LEDs and this caused a little shift as you can see from the image. Dot/Bar switch determines the operation mode of LM3915.
PCB is 1:1 scaled. You can print and transfer without making any change.
Here you can see the performance of the VU Meter in bar mode,
10 LED VU Meter in Bar Mode from Circuit Projects on Vimeo.