It used to be a must-have on any hi-fi, a pair of moving coil meters or LED bar graphs, the VU meter. Your 1980s boombox would have had them, for example. VU, for “Volume Units”, is a m… ...

The simple audio circuit used for the VU is based on the LM3915. You’ll find full plans on the site or you can watch the overview video embedded below.

The IN-28 VU-Meter comes with the LM3915 which has a logarithmic scale of 3 dB, starting from -27 dB to 0 dB in 3 dB steps.