Using some LM358 op-amps to do a "precision rectifier" circuit with this little VU meter board I got. Basically gets rid of the voltage drop caused by the diode which rectifies the audio signal into DC (so that it can actually display it without needing to be incredibly loud).
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The great thing about these amps is that they can run on a single unipolar power supply, and they're super cheap. I don't care about noise because it doesn't need to be incredibly precise (and with ten LEDs it's low resolution anyway)