Home Theater/optical cable
Recently purchased sound bar for tv system [not an expensive one].
I have sound connected using headphone socket and the typical red and white cables. Will using an optical cable [not included in box] give me any improvement in sound.
It may or may not - it depends on how the sound bar and television are signaling and what you're sourcing from. If you're just watching standard TV (which is generally broadcast with stereo audio), unless you have interference issues with the analog cables, it won't do anything for you (optical would prevent many interference issues from happening because it is immune to RF and also means the devices are electrically isolated from one another).
However, if the soundbar supports decoding of multi-channel audio signals (e.g. DTS; this is not an entirely uncommon feature), you may have somewhat improved performance if the soundbar is able to get the mutli-channel signal and apply its own downmixing/processing as opposed to just taking a stereo signal. Additionally, if your soundbar system includes a subwoofer, you will very likely have the true LFE channel (the ".1") as opposed to relying on a fixed crossover (many multi-channel decoders, like those found in DVD players, will actually "drop" the LFE channel when outputting analog stereo, which isn't a problem if you're hooked up to TV speakers (which generally can't reproduce bass anyways), but if your system can support low-end extension, having that data available can lead to somewhat better bass definition (quality)).
Finally, if the soundbar has more advanced DSP processing features (some Yamaha models, for example, fit into this category) they may have more configuration options if the signal is received digitally, although this shouldn't directly relate to overall quality (that is, the speaker component of the soundbar will sound as good as it does no matter what, but having more options when setting it up may let you better tailor it to your liking).
My advice then would be to check the owner's guide regarding the decoding capabilities of the soundbar, and consider your source components - if the manual mentions that it can only decode stereo PCM audio, you probably won't realize any advantages beyond interference rejection (and if you have an issue with interference, you would very likely know about it (it usually manifests as hum or buzz)) , but if the device offers more decoding features via digital input, it might be worth testing out. The advantage here is, optical cables really don't vary - they will either work or they won't work. So getting something that will work shouldn't cost more than a few dollars, and may be worth trying out in general if you're curious about the differences in sound. Here's an example of a well put together model that even includes dust-caps (to protect the ends when it isn't being used):
Generally the super-expensive models you see in hi-fi shops are more the result of retail mark-up than any form of tangible sound quality enhancement - some models may have more robust connectors, but this is usually not a benefit in everyday use (for example, some of the higher-priced Monster Cable models have spring-loaded connectors, which provides fantastic strain relief, but unless you're going to be plugging and unplugging the cable frequently, or it's going to be used somewhere prone to a lot of vibration, motion, etc, it probably will not provide any advantage to you). Be aware that on the other hand, some models do not have a standard style plug, and will come disconnected fairly easily (no influence on sound quality, beyond that they disconnect and therefore no signal is passed). The "correct" end for a TOSlink cable is six-sided, and somewhat squared off, like this:
(the Belkin linked above has this style connector; what we're looking at is the black plastic around the gold pin)
While some models have a circular end, like this:
(notice that instead of a squared-off shroud, it just has a circular shape)
Often the circular cables are touted as allowing the user to see if a signal is present, as a portion of their base will illuminate as well, the downside is that they generally don't stay connected as well.
If you have further questions, feel free to ask.