For a low part count simple VU meter Schmitt Triggers are the way to go. For n LED’s it only uses
1 capacitor optional
1 diode optional
and of course n LED's
Op amps work great but you can only drive four LED’s per 14 pin DIP.
LED drivers cost $6 or more per chip.
The purpose of using a Hex Schmitt Trigger is that it is easy to find and drives six LED’s per 14 pin DIP,
this keeps board space down.
The SN74HC14N Hex Inverting Schmitt Trigger chips I used only cost $0.63 per chip.
Step 1: Building the Circuit
Also I used round LED's (I have not bought the rectangular ones yet, I know they look better
green yellow red of course)
The resistance values are not crucial as long as the one to ground is close to the sum of the others.
(I used two 100k&’s in parallel to get 50k).
You can adjust the ground resistor to get less or move sensitivity. It has A diode detector to smooth blinking of the LED’s from fast paced music, and it is optional. A larger caparitor slows down the response time so greater than 4.7uF is not good to use. (If you cand find one small enough shunt the cap with a few k& or a varible and adjust to you taste.