What's the best way to "add" together both channels of stereo sound into mono?

I'm making a VU meter and I don't want to replicate my circuit for both the left and right channels of audio.  I'd like to just "add" together both channels so I can view them on the meter together.

rickharris6 years ago
You should be able to sum them across a resistor.
Joe426 (author)  rickharris6 years ago
Can you elaborate and/or provide a useful link?

A discussion here

A variety of circuits here
orksecurity6 years ago
The best way is probably a simple op-amp mixer. One chip and a few resistors.