Essence STX audio balance and hum

You may have to excuse the noobishness, I change sound cards once every complete orbit of Pluto around the sun.

Got a new rig very recently, and threw the Asus Xonar essence STX into the mix.
Trying to get my audio to work properly however is turning out quite difficult: my speaker system is a 2.1 that connects to a volume/bass control unit, pretty standard co-axial business.

There are two 3.5mm green jacks that would then connect to the computer; both speakers are tied to one, and the 2nd jack is the aux.

Plugging the aux into SPDIF gets me a loud buzzing, until I plug the speakers into either the L or R ports on the sound card, which I then get sound from that corresponding side, but not the other, and no bass. Plugging both into the L and R ports respectively gives me precisely nothing.

I'm also experiencing low level hum, which I believe is not uncommon. I wish I could pretend to know what the numerous Google search results are on about, but I know nothing about sound cards.


What am I doing wrong?

You probably need a Y-splitter cable to convert from the green stereo 3.5mm to two mono RCA plugs, which is how speakers are connected to the STX (L&R)

Aaaaaah yes that sounds good.

A splitter that turns 1 female into 2 male connectors would fill the L and R sockets, while leaving the aux to fill the SPDIF. Assuming I've got that the right way round...

Simple yes thank you

edit:
At first I confused myself, but then I remembered the card did happen to come with a splitter that would allow me to turn the one male jack that my speakers were sandwiched into, into the pair of male heads that would allow me to fill the L and R sockets, while leaving the aux to go hang out in the spdif. Hurrah for a bloody good sound card, and the power of communal assistance!

You shouldn't have to do anything with the other (aux) cable, it's for connecting things like consoles, phones, DAPs, etc.