Need help with a VU meter analog signal
You need to decouple the AC signal and then impose a DC bias onto it.  All you need is a capacitor and two equal resistors:







simulate this circuit &ndash; Schematic created using CircuitLab

The resistors create a "mid point" voltage of half the supply voltage (2.5V), and the input voltage is added to (or subtracted from) that midpoint voltage.

If you want to boost the signal you can pass it through an op-amp in non-inverting mode with a 2.5V DC offset. There's many schematics online for that - google "op-amp non inverting single supply"

Also, to increase sensitivity, you can use 3.3V instead of 5V, set the ADC to use the EXTERNAL voltage reference, and connect the 3.3V power into the Aref pin.