Is there a way you can add 5.1 audio to Auxiliary Inputs?

Auxiliary inputs to a receiver are always stereo. If you have a 5-channel analog signal (from a computer or other multi-channel device), you will need a receiver with a 5.1 analog input. This has 5 separate RCA inputs for left, right, center, sub, and the two surround speakers.

An analog output from a VHS-Hi Fi VCR can be input into the stereo aux inputs of a receiver and decoded to Dolby Surround, but this format is actually only 3 discrete channels, left, right, and surround. It has no separate information for the sub or the center channel, and has a limited bandwidth on the surround channel.