Beginners' Guide to Audio Connections

Compared to the confusing ins and outs of digital video connections, home-theater audio connections are relatively straightforward. Still, there are a few wrinkles you'll need to consider before wading into your local electronics store, credit card in hand.

Digital audio connections: If you want true 5.1, 6.1 or even 7.1 sound from your home theater—that is, five or seven discrete channels of sound, plus a ".1" channel for your subwoofer—you'll need to use the digital audio connections on the back of your receiver (assuming, of course, you have a 5.1-capable receiver). These connectors typically come in two types: optical (a.k.a., Toslink) and coaxial, and you'll find them (typically both, although sometimes only one or the other) on almost every DVD, Blu-ray, and HD DVD player out there, not to mention DVRs, TiVos and the latest gaming consoles.

Optical connectors look like small, squarish holes (often protected by plastic flaps) with a pair of notches on the sides, and if you look at one end of an optical digital audio cable when the other end is connected to your receiver, you'll see a little red light; that's because the digital signal carrying the sound is being transmitted via fiber-optic cable. Kinda cool. Connect your DVD player, DVR or game console to one end of the optical cable (it should snap right in) and plug the other end into your receiver, and you should be in business.

Coaxial connectors are really just your friendly neighborhood RCA plugs; nothing too special here, except when you plug the cable into a coaxial digital audio output, it'll deliver 5.1- to 7.1-channel surround sound to your receiver, same as with optical digital audio cables.

So, is there a difference in sound quality between optical and coaxial digital audio connectors? Depends. According to the experts at Audioholics, optical cable do better in situations where your cable needs to run further than 10 feet, or when the cable is sitting close to other video and power cords (pretty likely) that could cause interference. On the other hand, optical cables are considerably more expensive and delicate than coaxial cables. In my experience, both sound great; maybe dogs can tell the difference, but I sure can't. Usually, your choice between optical and coaxial will be dictated by your components; for example, the Xbox 360 gaming console has an optical—not coaxial—digital audio output.

Now, there's another wrinkle I need to mention: HDMI connections. HDMI is capable of delivering both video and digital audio over a single cable, although not all AV components can handle audio as well as video over HDMI. If your receiver and DVD/Blu-ray/HD DVD player can deliver both audio and video over HDMI, you should be able to skip the optical and coaxial connections altogether.

Analog audio connections: Look behind your receiver, next to the digital audio connectors; you should find a series of analog audio inputs, probably one set for each of your various video inputs. Audio inputs use the same RCA-type jacks as coaxial digital cables, except instead of just one jack per input, you'll find two: one labled "L" for the left channel, the other marked "R" for the right channel. Plug the two jacks in, making sure the cable coming from the "left" channel of your DVD player, DVR or gaming console matches the left channel jack on your receiver, and the same with the right channel. Most analog connections give you only two-channel sound, versus 5.1 or 7.1 channels for digital audio (see below for an exception); however, most modern receivers use Dolby Pro Logic sound processing (or Dolby Pro Logic II or IIx) to turn two-channel sound into simulated four-, 5.1-, 6.1- or 7.1-channel sound. Why use the analog connections if they only deliver two-channel sound? In general, you shouldn't have to unless you're dealing with, say, an old cassette deck, a VCR or a turntable that only puts out two-channel analog audio.

If you happen to have a high-end AV receiver, you may find a cluster of six analog RCA-type audio connections; these are for devices that deliver multichannel analog sound (such as DVD-Audio and SACD players, a pair of high-resolution audio formats that never quite caught on). 

Want to learn the nitty-gritty of AV connections, along with a variety of connection types that I didn't cover? Check out the AV University at Audioholics for an exhaustive series of articles and tutorials.