Samsung le37b551a6w 5.1 suround sound

[sam.q.miller]

Hi, new here.
Im having trouble setting up my Logitech Z506 5.1 surround sound speakers to my Samsung le37b551a6w tv.
Ideally, id like to have 5.1 surround sound when im streaming off my amazon firestick plugged into the back of the tv, and when I dual screen on my pc (to tv).
At the moment I have a optical cable coming out of the tv into a 5.1 audio gear digital sound decoder going to 3 x 3.5mm jacks which go into the FL/FR SL/SR CEN/SW ports on the speakers. Also a HDMI from my laptop to tv.
Is it a case that my TV can only output 2.1? On the specs it says it is Dolby digital plus compatible does this have relevance?
Will i need to get a different decoder with a HDMI in it to run through that to the TV?

Sorry for all the questions and if they're silly!

A very confused student

 

[americanaudiophile]

Check the audio menu of the TV. Try a different setting. Bitstream is usually 5.1
You will need to make sure that the content you are viewing regardless of the source is Dolby Digital. The decoder you got may not default to Dolby ProLogic when receiving a stereo source the way an AV receiver does.
If the TV won't output 5.1 then using HDMI ARC won't help. You would need an HDMI input selector with audio extraction to provide an audio output from your sources that doesn't go through the TV.