Will your tv sound better with a optical cable?
The answer depends on a number of factors. Firstly, it depends
on what the original audio source is. If the source is an analog
one, connected via RCA or phono connectors, then a digital optical
audio input may be an improvement. In most cases, video equipment
today uses a digital source so the audio will be in a digital form
until it is converted to analog and fed to the RCA connectors.
If an optical link is used, the digital data is preserved until
it reaches the amplifier inside the television where it is
converted to analog. The analog conversion always happens somewhere
before the sound is delivered to the speakers so it is impossible
to keep the sound in a digital form all the way through the signal
chain.
Although digital audio has been hailed as a way of improving
quality, the quality loss in a pair of RCA cables is minimal so
telling the two apart will be difficult or impossible in most
situations.
If an optical link is being considered as an alternative to
HDMI, there is no benefit of any kind. Both carry audio as a
digital signal so there will be no difference in quality. Both will
be converted to analog for amplification and until that time, the
signal data will be identical, regardless of the route it
takes.
Note: Audiophiles will say that digital audio data can be
affected by the type of cable or optical link used or by the cable
used for analog links. These claims have not been proven or
dis-proven. The answer above ignores claims of this type as the
effects are so minimal that most are unable to be measured by any
conventional test equipment.