Digital audio cable is used to connect audio source components of a home theatre to the receiver or preamplifier. The significance of using digital cable is that it is necessary in order to transmit a surround sound signal. Analogue cable is not designed to support digital surround formats like Dolby Digital. The only difficult part about connecting digital audio cable is choosing from the three types. After that, it's merely a matter of plugging each end into the right jack.
Familiarise yourself with the three types of digital cables. The premium choice on today's market is high-definition multimedia interface cable (HDMI). This cable supports more formats and is also the preferred method of transmitting HD video. The other options are digital coax and optical cable. Both provide quality audio, though some prefer one over the other.
Decide which cable you can use. The most important consideration is what connections you actually have available. Check both the audio source outputs and the home theatre receiver inputs to determine what type of cable to use. Digital coax is usually an orangish-yellow RCA jack. Optical terminals are covered by a small, removable plastic plug and emit light when the plug is removed. HDMI is a long, flat port that should be labelled as HDMI. Before committing to a cable, be sure that both pieces of equipment are designed to accept it.
Consider other factors. HDMI is the most versatile, top-end digital cable. However, it's not included on much older equipment such as DVD players and CD players. Receivers may not have an input available either.
One factor that limits the utility of optical cable is that it operates via light and won't work properly if bent. Optical is also more expensive than coax.
Purchase the cable that you decided on. You can find cables at any reputable electronics store or online retailer.
Connect the cable. To connect, shut off all the electronics, plug one end of the cable into the proper output jack on the audio source and then plug the other end into the input on the receiver.
Hook up video. If you're using HDMI cable, you will also be routing the video through the receiver. In this case, you'll need a second HDMI cable to output the video to your TV. For instance, if you're connecting a Blu-ray player, plug the first HDMI cable into the Blu-ray output and then into the receiver's HDMI input. Then connect a second cable between the receiver's HDMI output and the HD television.
Double check that all connections are secure. To test to make sure that everything is working, turn on the audio source component and the receiver. Switch the receiver to the appropriate input (i.e. "CD player") and try playing the source. You should get clear sound out of all speakers.