Digital Audio Cables

One of the significant developments with the widespread adoption of the personal computer for home, business, and school use is the digitalization of media and the subsequent mass adaptation by consumers and industry. While digital media is not a new concept, it has only recently made its way into the “normal” household and is commonly supported by digital audio cables. As a result, higher quality audio playback is now supported while watching movies or listening to music that can approach (or at times exceed) the experience found in a high-end movie theater. While architecting the perfect home or work audio setup, some consumers neglect to identify the proper digital audio cable (vice analog) to use in their respective entertainment system.

What Are the Types of Digital Audio Cables?

The two most common types of digital audio cables are coaxial and optical digital audio cables (also referred to as S/PDIF). Coaxial digital cables are the more commonly found type of cable and are very similar to the legacy, RCA analog type which most consumers have experience using. The primary difference between RCA and coaxial tends to be the thicker shielding required in the cable to prevent interference from outside noise sources.

How Do Coaxial Digital Audio Cables Work?

Coaxial digital audio cables allow signals to be transmitted in pulses of electricity through copper wires that are contained inside of the housing of the cable. The coaxial cable contains aluminum wraps that are engineered to block outside signal interference. The typical impedance for audio applications is 75 ohms and the cable type permits a larger overall bandwidth than an equivalent RCA cable. For the average home consumer, coaxial cables cost less than the optical S/PDIF type and are the most commonly used for home or personal digital audio needs as a result.

How Do Optical Digital Cables (S/PDIF) Work?

The other type of digital audio cables are optical digital cables or as they’re more commonly referred to S/PDIF. These cables are completely different from any kind of cable most people know since they do not make use of a conductive metal such as copper. Instead, S/PDIF cables use pulses of light to transmit signals. The primary advantage to this mode of information is the elimination of radio and electromagnetic interference. As a result, the cables do not require as thick of shielding as the coaxial type. Another advantage of the S/PDIF type is that there is no degradation of signal over distance resulting in the same quality of signal exiting the cable as entering it. As a result, many audiophiles prefer the use of optical cables over coaxial. One significant shortcoming of the cable type is that if the optical cable gets bent, it can become damaged if installed in a high traffic area. The majority of modern audio components are built with ports for both S/PDIF and coaxial cable inputs and outputs.

HDMI Cables

HMDI (High Digital Multimedia Interface) cables have traditionally been used to carry digital video. They are also capable of transmitting audio; however, this is most commonly associated with the audio tracks most commonly associated with the video. HDMI ports are found primarily on DVD players, HDTVs, and some personal computers. The cable can support up to 5 gigabytes per second of bandwidth so it is able to transfer from the source (high definition DVD player) to the your HDTV a pure A/V signal without any compression of the signal. Ultimately, HDMI may replace all digital audio cables as support for the cable for audio components as it reduces the need for separate video and audio cabling. Although HDMI usage has been increasing, many components are still being produced which only use the HDMI port to send or receive video and have not yet hit the mainstream for digital audio usage.

How to Choose Between Coaxial and S/PDIF Cables?

If your components support both coaxial and S/PDIF digital audio cables, a common decision point that consumers have to make is which cable type to purchase. Some common considerations are:

1 – The amount of electromagnetic interference in the environment. If your cables will be run near other power cords or a personal computer that transmit radio frequency noise, then an optical cable will have better performance than coaxial.

2 – Distance or length of audio cable to be used. Optical cables provide better sound quality over distance when compared to coaxial. If you need to run speaker wire for distances exceeding 10 feed, then optical cables will provider higher sound quality.

3 – Budget. For consumers who are approaching, met, or exceeded the budget for a home entertainment system, coaxial cables will be a more economical choice when compared to S/DIF.

4 – Sound set-up requires cables to be bent. If your specific entertainment set-up requires the cables be bent, coaxial cables will be the preferred choice.

5 – Sound system will be moved frequently. If the sound system will be moved frequently, the possibility of optical cables being damaged significantly increases. As a result, coaxial cables will be the preferred choice.

Other Factors to Consider when Choosing Digital Audio Cables

Listening Environment

A significant factor to consider before spending money on more expensive audio cables is what type of environment the cables will be used. If the audio system will be used in an environment with a significant amount of background noise, it will be harder for most consumers to tell the difference in quality between coaxial and S/PDIF cables. If the consumer is older, paying consideration to one’s actual hearing capability should also be made. If one cannot tell the difference in sound output in the store (between coaxial and S/PDIF cables), then the likelihood of doing so in the home is low.

Speaker Quality

Another common mistake made by consumers when choosing digital audio cables, is ignoring the quality of the entertainment system’s speakers. If possible, testing the performance of speakers with each type of cable is recommended before spending money on the more expensive optical cable.

Quality of Audio Content

Another common mistake made when choosing digital audio cables is the quality of the music media itself. Many a consumer has purchased high-end audio equipment at the store along with optical cables and then plays music from low-quality sources such as YouTube, converted MP-3s, and other non-digitally sourced music. Just because a song has been ripped to MP-3 or even MP-4 does not mean it has been produced to the quality required to take full advantage of a high-end audio playback or entertainment system.

Digital Audio Sources

The majority of music legally purchased or downloaded online is in a “lossy” format. MP3 and the 128 kbit/s AAC format found on iTunes are lossy containers. Although this quality of recording is sufficient for playback on less expensive audio systems or MP3 players for pop music, it is not the highest quality of recording available. For a truer or better audio experience, the digital audio track needs to be recorded in a lossless format such at FLAC with an encoding of 320 kbit/s.

The problem is getting that high quality audio, which is ironically harder to do today than it was in the days of analog audio. The majority of music popular with the public is either not available in a lossless format, or costs additional money to purchase. If you already have a significant MP3 or music library, it can prove cost prohibitive to repurchase the same music in the higher quality.

If the consumer only listens to popular music; however, his or her ears may not be able to tell the difference in encoding rate. The sound differences with encoding options are easier for the average person to differentiate while playing back classical music on the audio system. Before expending significant funds to acquire a new music library, consumers should actually test several songs of the preferred genre encoded at the 128 and higher rates to see if there is a noticeable performance difference.

Supporting FLAC Audio Playback

Before spending a significant amount of money on purchasing music encoded in FLAC format, consumers will need to ensure they have an encoding program that supports FLAC. Two of the more popular, free, options for encoding music in this format include Audacity and the VLC Media Player. These applications are generally operating system agnostic and support computers that run OS X, Windows, and Linux operating systems.  Other cross-platform playback options include MPlayer and Songbird. Popular Linux specific players include Banshee and Audacious.

Digital Audio for Movies

When designing or purchasing a home entertainment system, the quality of audio playback should be considered to provide an enriching audio experience to complement the HD playback of movies. The DVD/Blu Ray player will need to support digital audio in order to best leverage a high-quality sound system for movie viewing. When choosing a player that supports digital playback, consumers need to ensure it supports a digital audio cable connection that is compatible with the audio playback system. The majority of HD movies that come on disc or are purchased online also support digital audio.