How does an audio receiver 5.1 surround sound processor separate the channels of analog audio stereo signals?

Question

I was listening to Vinyl and realized I forgot to switch my receiver from 5.1 to Stereo and was amazed at how the receiver separated the 5 channels and made records from 40+ years ago sound like they were recorded in 5.1 with such spacial sound. Some instruments/vocals were only playing from the rear speakers and was curious how it was able to do that since it was an analog signal.

In: Technology

Answer 1

Read About Dolby Pro Logic II for one example. It can blend channels together to ‘unfold’ a stereo signal into surround sound with center and rear channels.