Sorry about the extra jargon.
A sound card is the plug is device that controls the audio features of your tv.
These flat screens are just computers with a lot of inputs and outputs. There are sound cards, video cards and such that make everything work.
I only mentioned optical because while the connection is pretty easy and reliable, depending on the age of the TV, optical may only give you what amounts to stereo.
Another feature Consumer Electronics Control (CEC) works to help bring devices in line with the TV. Control can be done by a single remote.
HDMI Audio Return Channel (ARC) is how you get sound between your tv and your speaker over higher quality HDMI cables. The signal has more channel capacity than stereo and is better sounding.
I suspect your problem may be related to how your TV sends audio to your speaker through the Audio Return Channel.
The HDMI cable actually handshakes with the devices. Make sure CEC is turned on both the speaker and tv. You may need to do a reset or handshake to get the devices talking. That procedure is explained in this string.
Getting the sound over HDMI is better than optical plus you get the added feature of unifying control of your devices.
Hope this helps.
