In today’s home theater environments, quality audio is paramount. In the old days, you could connect your tape deck or CD player via simple red and white analogue component cables. These are still used today for many sources, but there are better alternatives.
Each RCA cable represents a channel of audio and so the red and white cables represent left and right audio channels. This works fine for simple two channel audio. The problem is that home theater audio has between 6 and 8 channels. In theory, you could still have six separate audio component cables, but this gets complex rapidly. The first DVD player I had included a built in AC-3 decoder and had six separate RCA output channels.
The other solution work, but is not efficient. Imagine if you had multiple AC-3 components like a DVD player, cable box and videogame system. Now you would need 18 cables (6×3) which is very complex and inefficient. A solution to this problem is another technology called an optical digital audio cable or more commonly known as a toslink cable. Here is a picture of a toslink cable courtesy of Monoprice which is a very inexpensive place to purchase these cables.
The other alternative to the Toslink in another cable type called digital Coax. This cable is interesting because it combines the benefits of multi-channel Toslink and with convenience of RCA connections. Basically this connection type includes what looks like a traditional RCA connector and traditional RCA cable. The different is that while you plug in standard RCA cables, the actual signal sent across the cable is digital allow for 6 or 8 channels over one cable. In many respects this is the best of both worlds, by allowing Toslink density without the need for a special cable. Unfortunately, in my experience these types of connections are less common and instead Toslink has become the standard. Note that like Toslink the signal is binary and so a cable will either work or not. I say this because many vendors will try to sell you high priced cables for this. Do not be fooled, they maybe helpful if you are running long distances, but these provide limited value in most environments. In my setup, I am just using an extra RCA cable that I had hanging around and it works perfectly.
What does this mean to me?
The answer is that you should be aware of the important of Toslink or Digital Coax cables and make sure that any receiver you purchase has a full complement of these.