You’ll need either an LM3915 or LM3916 chip, a couple of bread boards, two audio jacks, ten LEDs, and a few other components. Wire them all together per the schematic, then plug an audio source into the input jack. You can plug your speakers or output device into the output jack, and you’re done. Keep in mind that LM3916s switch negative, so positive to positive wiring from LEDs to the bread board will be necessary. The wiring on [Joe]‘s version is a bit convoluted, but it can be cleaned up on yours if you take the time. Video embedded below.
This VU meter project by [Daniel Naito] is a great piece of Russian electrocouture. It’s made up of 14 Nixie tubes that display seven frequency bands for the two audio channels. He found this similar project, but wanted to keep the cost low by avoiding such exotic ICs. First, the two input channels are amplified and then split using seven bandpass filters covering 60, 150, 400, 1000, 2500, 6000, and 15000Hz. Then, the AC audio is converted to DC. The final stage converts the logarithmic scale to a linear output. Besides the semirare Nixie tubes, the majority of the parts are just cheap opamps and comparators. The post is an excellent read and you can see it in action in the video below.