How to connect 5.1 audio to iMac?

Question

Audio

There is an old iMac (late-2009) with a combined 3.5mm audio output. Both headphones (or another device for outputting analog sound) and some kind of digital optics can be connected to it.
Actually, the question is: how to connect a 5.1 speaker system there? That is, how to get 3 standard 3.5mm outputs from this combined audio output?
Thank you!

Answer 1

for HDMI (5.1): you need such an octopus
for 3xRCA: this is a miracle and an adapter