Not very long ago, a discussion of digital source components was confined to a single format: the compact disc. But today’s music lover is faced with a proliferation of new digital formats, from terrific-sounding high-resolution media such as SACD and DVD-Audio, to lower-quality carriers such as MP3 players and computer-based audio. Technology has also changed the way we access digital music; hard-disk-based music servers now give us instant access to our music libraries without removing a disc from its case and inserting the disc in a player. The iPod and other portable music players allow us to take our music collections with us wherever we go.
This section will guide you through the various formats for accessing digital music, explain how they work, and provide advice on how to choose the best digital components for your system and budget.
Compact Disc
When the compact disc was introduced in 1982, many music lovers found its sound inferior to the “crude” technology of vinyl records. CD’s marketing slogan, “Perfect
Sound Forever,” seemed like a cruel joke. But despite the fundamental limitations of CD, its sound quality has steadily improved to the point where it now can be musical and enjoyable. In fact, just since the turn of the millennium, CDs have taken a big leap f the result of higher quality mastering formats and techniques. Despite the explosion of new digital-audio formats since the CD’s introduction in 1982, the CD continues to be the primary medium by which most of us listen to music.
But getting the best sound from your CD collection requires a player capable of extracting all the information on the disc and presenting it in a musical way. The differences in sound quality between players is significant, and choosing the best player for your system is an important aspect of building a system that will give you years of musical enjoyment.
Although the sound quality on compact discs themselves has greatly improved, the quality of CD playback hardware has, in one respect, declined over the past few years. This trend is the result of the explosion of the DVD format and the staggering price-to-performance ratio of today’s DVD players. Video-processing circuitry became simultaneously more advanced and vastly less expensive, due to large-scale manufacturing of integrated circuits. In fact, the same video-processing circuitry that once cost $10,000 in a stand-alone video processor is routinely available in DVD players costing well under $100.
But how does this trend toward better and cheaper DVD players affect the sound quality of CD playback?
Most consumers today buy a single machine that plays DVDs, CDs, and perhaps other disc formats. For many, the DVD player serves as the source for CD listening. As DVD players got cheaper and cheaper in a highly competitive market segment, the designers cut corners on the audio circuitry. The parts in a DVD player that affect sound quality when playing CDs include the power supply (a large and heavy section), the audio amplifiers, passive components (primarily resistors and capacitors), and a host of other devices. These parts have become more expensive over time, not less so. Consequently, a $100 DVD player’s audio-parts-quality is abysmal, and the sound quality often reflects this fact.
The solution is to choose either a dedicated high-end CD player, or a DVD or multi-format universal player with high-end parts and design. Many specialty audio companies offer DVD players with outstanding audio sections that were not thrown in as afterthoughts, or put together with whatever parts budget was left over after the video circuitry was designed. Despite this global trend toward lower-quality CD playback, high-end CD players have never sounded better, or been a better value than they are today.
High-End CD Playback: Dedicated CD Players and Separate Transports and Processors
As previously discussed, a dedicated CD player (one that doesn’t play other formats) will generally deliver better sound quality than is possible from a DVD player or universal machine. There are some outstanding universal players, but they are the exception rather than the rule.
If your focus is on 2-channel music listening, you’ll probably choose a CD-only playback system. If so, you have two choices: a CD player or separate CD transport and digital-to-analog converter (also called a digital processor). A CD transport is simply a CD player without digital-to-analog conversion circuitry. It outputs a digital signal that is converted to analog by the outboard digital processor, housed in a separate chassis. Needless to say, this approach is considerably more expensive than buying a CD player.
But are “separates” worth the price? If you have a large budget and want the best possible performance, the answer is yes. But CD players are generally a better value for two reasons: 1) By combining the transport and processor in one chassis, with one power supply, one front panel, one shipping carton, and one AC cord, the manufacturer can put more of the manufacturing budget into better sound; and 2) A CD player has no need of a sonically degrading digital interface (cable) between its transport and processor, which means that it might have better sound.
A CD player also makes your life much simpler than owning separates. Rather than requiring two chassis in your rack, two power cords, and a digital interconnect, the CD player lets you focus on the music rather than on the equipment.
Many excellent CD players are available for under $500, including some legitimate high-end machines that sell for as little as $300. This is, however, the lower limit of true high-end CD players. Below this level you enter the realm of mass-market products designed for maximum features and minimum manufacturing cost, not musical performance. You should also avoid multi-disc players; most manufacturers cut corners in sound quality to cover the extra expense of the disc-changing mechanism. The single-disc player will provide better sound quality for the same price, and also better ultimate fidelity—single-disc transport mechanisms can be made better than carousel type changers. If, however, you’re set on a changer, consider using it as a transport to feed a high-quality outboard digital-to-analog converter. A few CD changers can be called high-end, but they are rare.
Separates offer several advantages over one-box CD players. First, they allow OU to upgrade the transport and the processor independently. Second, putting the sensitive digital-to-analog conversion electronics in a separate chassis from the mechanical transport lowers the chance of polluting the analog signal with digital noise. Third, the cutting-edge design work takes place in separates, not CD players.
Those arguments, however, are less compelling in light of what’s been happening in CD-player design recently. Designers are now applying the same level of parts and design quality to CD players once reserved for separates. These premium parts and techniques include large and well-regulated power supplies, high-quality DAC (digital-to-analog converter) chips, and the designer’s best analog circuits. Moreover, many innovative design techniques are starting to appear first in CD players. The CD player is no longer automatically the entry-level product in the digital manufacturer’s line, instead it’s become worthy of the manufacturer’s best efforts.
High-Definition Compatible Digital (HDCD)
Some CD and universal multi-format disc players are touted as being “HDCD Compatible.” This designation means the player will decode CDs encoded with the High-Definition Compatible Digital process. Recordings encoded with HDCD can be decoded and played back on any CD player, with some improvement in fidelity. But if your CD player is equipped with an HDCD decoder, HDCD recordings can be reproduced with much better sound quality than is possible with conventional CDs.
Digital Connections
The S/PDIF (Sony/Philips Digital Interface Format) interface is a method of transmitting digital audio from one component to another. For example, a digital transport’s S/PDIF Output 15 carried down a digital interconnect to the S/PDIF input on a digital processor.
Digital connections can be divided into two categories: electrical and optical. In an electrical connection, electrons carry the signal down copper or silver wire. An optical connection transmits light down a plastic or glass tube. Both types carry the same S/PDIF format, but in different ways.
The most common type of connection, coaxial, is carried on an RCA cable. This is the electrical connection found on virtually all CD transports, most good CD players, and other consumer digital audio products such as digital preamplifiers, room-correction systems, and digital recorders. TosLink is the low-cost optical interface promoted by mass-market audio manufacturers as an alternative to coaxial connection. TosLink, a trademarked name of the Toshiba Corporation, is more properly called “EL Optical,” after the Electronics Industries Association of Japan. Fig. 1 shows coaxial and TosLink digital outputs as you would find them on a CD transport, DVD player, or universal disc machine.
A digital source’s output can be on an electrical coaxial
output (left) or on an optical TosLink output (right).
Note that coaxial and TosLink interconnects can carry S/PDIF from a CD transport to a digital-to-analog converter (or from a CD player to an A/V receiver), as well as a Dolby Digital or DTS bitstream from a DVD player, satellite receiver, cable box, or other audio/video source to an A/V receiver. If you connect a coaxial or TosLink cable carrying Dolby Digital to a digital-to-analog converter that expects to see S/PDIF from a CD transport, you’ll hear a blast of noise.
There’s a third interface, found only on upper-end components, called the AES/EBU interface, which is carried on a balanced line terminated with three-pin XLR connectors. Of the three conductors in a balanced signal, one is ground, one is the digital signal, and the third is the digital signal inverted. Virtually all transports and processors have RCA jacks, and most include TosLink for compatibility. AES/EBU is usually found on only the more expensive components, or offered is art option on mid-priced digital equipment. Image shows these interlace types.
TosLink is the least good interface, mechanically (the physical connection between cable and jack), electrically, and sonically. TosLink connection tends to blur the separation between individual instrumental images, adds a layer of grunge over instrumental textures, softens the bass, and doesn’t have the same sense of black silence between notes. Our advice is to avoid Toslink unless you have components equipped only with TosLink connections, or you’ve run out of coaxial digital inputs on your AVR.
But how can a digital interface, that merely transmits ones and zeros, change the sound? If the ones and zeros are the same (which they are), doesn’t the sound have to be the same? How can a digital system, where the music is represented by ones and zeros, exhibit an analog-like variability in sound quality?
Digital signals are carried on cables terminated with
RCA connectors (left),TosLink connectors (middle), or XLR connectors
(right).
The answer is that the digital interface makes no sonic difference if the audio data are being transported from one device to another and not converted to analog for listening. The problem arises when we listen to digital audio that has been put through a digital interface because the interface introduces jitter. The term jitter refers to timing errors in the clock that controls when the CD’s digital samples are converted into music. Musicians say that “The right note at the wrong time is the wrong note,” and this perfectly describes the jitter problem in digital-audio reproduction. If the digital samples are converted into an analog signal (music) with a jittered clock, a form of degradation is introduced.
High-Resolution Digital Audio: SACD and DVD-Audio
Despite the advances made in the past few years, CD sound quality is fundamentally compromised by its sampling rate of 44.1kHz and its word length of 16 bits. The sampling rate determines the highest audio frequency that can be encoded, and the word length determines the system’s dynamic range, noise level, and resolution. Digital audio systems with higher sampling rates and longer word length sound significantly better than CD, whose parameters reflect late-1970’s technology.
High-resolution digital audio is generally defined as any system with a sampling rate of 88.2kHz or greater, and word length of 18 bits or greater. The highest sampling rate and word length in use today is 192kHz/24-bit. That may seem overkill, but increasing the sampling rate and word length greatly improves the sound of digitally reproduced music. High-resolution digital audio has greater resolution of low-level detail, wider dynamic contrasts, more natural rendering of timbre, smoother treble, and a larger and more spacious soundstage.
Audiophiles have two choices in high-resolution digital: Super Audio CD (SACD) and DVD-Audio. Neither format became the mass-market successor to CD, but both still exist as niche formats. As of this writing, there are about 7000 SACD titles and 900 DVD-A tides available. If you choose to buy an SACD or DVD-A player, be aware that the formats will never generate a huge catalog of titles. New titles will be released slowly, and be primarily of classical music. Nonetheless, the sound quality from SACD and DVD-A is so good that it’s worth buying a player, in my view. Moreover, if you want high-quality multichannel audio in your home, there’s no substitute. There are enough wonderful high-res tides on the market to warrant investing in a quality machine. For a complete list of SACD titles, go to www.sa-cd.net.
SACD
An SACD’s information-carrying pits (right) are smaller and closer together than on a CD. Let’s first look at SACD. The format provides up to 74 minutes of 2-channel and 6- channel audio (6-channel is optional) on a disc the size of a CD. Where CD has a bandwidth of 20kHz, SACD’s bandwidth is 100kHz. SACD also has wider dynamic range than CD, with greater resolution of low-level detail. SACD doesn’t use conventional pulse-code modulation (PCM) employed on CD and DVD-Audio, but a different encoding technique called Direct Stream Digital (DSD).
A hybrid SACD contains a high-density layer and a conventional CD layer on the same disc.
SACD also offers the possibility (but not the requirement) of a “hybrid” disc containing two layers on the same disc for backward-compatibility with CD. One layer contains CD’s conventional 16-bit/44.lkHz audio and the second layer holds the high- resolution multichannel version. When you put a hybrid SACD disc in a CD player, it behaves (and sounds) just like a CD. But put the same disc in an SACD machine and you can hear high-resolution stereo or multichannel music. The hybrid disc ensures backward-compatibility with the massive installed base of CD players. This feature is made possible by two information-carrying layers on the disc, one high-resolution and one that is CD-compatible. The CD-quality layer is sometimes called the Red Book layer, after the color of the cover of the official specification describing the com pact disc. More information is contained in the second layer because the information- carrying pits are about half the size of a CD’s pits, are spaced closer together, and the information is recovered with a shorter wavelength playback laser
Note that some SACD players are 2-channel only; others will play both 2- channel and multichannel recordings. SACD playback is available in combination CD/SACD machines, as well as in some universal-disc players.
DVD-Audio
The DVD-Video format has been a massive commercial success, rapidly replacing VHS as the preferred movie-delivery format. As mentioned earlier in this section, DVD’s larger data capacity (nearly 18 gigabytes in its maximum form, 25 times that of CD) makes it possible to store high-resolution audio—the DVD-Audio format. Specifically, the DVD-A specification calls for a disc that can contain 6-channel music along with a 2-channel mix on the same disc, with a sampling rate as high as 192kHz and word lengths of up to 24 bits. You can think of a DVD disc as a “bit bucket” that can hold a wide variety of sampling frequencies, word lengths, playing times, and number of channels, all selectable by the disc’s producer.
Even DVD-A’s storage capacity and maximum transfer rate (how quickly the bits can be pulled off the disc) are not high enough to deliver multichannel audio with high resolution on all channels. To overcome this limitation, DVD-A employs a loss-less coding system developed by Meridian Audio called Meridian Lossless Packing (MLP). Unlike “lossy” compression systems such as Dolby Digital or MP3 that remove information and reduce fidelity, MLP is a perfectly lossless process, producing identical bit-for-bit data on playback with no sonic degradation. Using MLP is completely transparent to the user; you simply insert the DVD-A disc into player and the decoding is automatically engaged. More than 90% of all DVD-A releases are encoded with MLP. MLP is also the basis for Dolby TrueHD, a lossless system for delivering high- resolution multichannel audio on HD DVD and Blu-ray Disc.
Using a DVD-Audio player is somewhat different from playing an SACD. It is assumed that the DVD-A player is connected to a video monitor; set-up menus, selection of 2-channel or multichannel, and other parameters are chosen through a video- based menu system. Operating a DVD-A player without a video display can be challenging. Conversely, SACD machines have no such requirement. They operate just as a CD player would; pop in a disc, press play, and start listening.
Neither SACD nor DVD-Audio became a mass-market success, probably because the two formats competed against each other, and were incompatible. We will never see a huge library of titles in either format, but many audiophiles nonetheless choose an SACD or DVD-A player to enjoy the titles that are available.
DualDisc
A variation on DVD-Audio is the DualDisc format, a disc that combines a CD with DVD. As its name suggests, a DualDisc is composed of two discs bonded together. One disc contains conventional CD data, and plays on any CD machine. The opposite side is a DVD, which can contain video, high-resolution digital audio (with the same specs as DVD-A), graphics, or data. DualDisc can offer full DVD-A-quality audio and be backward-compatible with the world’s installed base of CD players.
Universal Disc Players
Many manufacturers have introduced universal players that are compatible with a wide range of disc formats, including CD, SACD, DVD-A, DVD-Video, and even discs on which MP3 files are stored. Universal players are a good solution if you want to enjoy the broadest possible range of formats and title selection.
You’ll find a number of compatibility variations in universal disc players. They include:
• CD, 2-channel SACD, and 2-channel DVD-A
• CD, 2-channel and multichannel SACD, DVD-Video
• CD, 2-channel and multichannel SACD, 2-channel and multichannel DVD-A, DVD-V
• CD, 2-channel and multichannel DVD-A, DVD-Video
For those seeking the ultimate in sound quality choosing separate machines to play each format is a better choice than the universal player. Although many offer excellent performance, they rarely equal the sound quality of dedicated single-format machines.
Multichannel Output on High-Resolution Players
All multichannel audio players (DVD-Audio, SACD, and universal machines) deliver their outputs in analog form on six jacks. This requires that you have an analog preamplifier, controller, or receiver with six analog inputs, and that you run six analog cables between the player and your preamp or controller. A few multichannel players have a digital output that carries high-resolution digital multichannel audio, but these multichannel digital interfaces are often proprietary, meaning that you’ll need a controller or receiver made by the same company to use this connection. Examples of proprietary multichannel high- resolution digital connections are Sony’s i.LINK and Denon’s DenonLink.
Image below is the back panel of a multichannel SACD player showing the 2-channel and multichannel outputs. You can also see the coaxial and TosLink digital output jacks which carry 44.lkHz/16-bit digital audio to an outboard D/A converter or to a controller or A/V receiver (described earlier in this section). The jack marked i.LINK is the proprietary high-resolution multichannel output that requires an i.LINK-compatible receiver.
hpas_5-5.jpg The rear panel of a multichannel SACD machine showing the analog multichannel outputs (top left), stereo analog outputs (bottom left), coaxial and TosLink outputs for CD-data only (center), and the i.LINK high-resolution multichannel output (right).
Note that most controllers and receivers offer just one set of multi-channel analog-input jacks; if you have two multichannel sources, you can connect only one at a time.
The newest generation of digital interfaces, High-Definition Multimedia Interface (HDMI), carries high-resolution multichannel digital audio. The interface was developed primarily to carry high-definition video as well as audio in a single, easy-to- use cable. The industry-wide acceptance of HDMI vl.3 solves three problems: 1) the need to run six analog cables between a multichannel source and your receiver or A/V controller; 2) the limitation of just one multichannel input on receivers and controllers; 3) the incompatibility between brands of equipment employing proprietary digital interfaces.
An HDMI cable (v1.3) can carry high-resolution multichannel digital audio from a digital source to an outboard digital-to-analog converter, A/V controller, or AVR. HDMI can also simultaneously carry high-definition video.
Bass Management in SACD and DVD-A Players
The term bass management describes a system in which bass is filtered out of some channels and directed to a subwoofer, if the system employs one. Bass management is necessary in multichannel audio systems, and is found in most SACD and DVD-A players, as well as in A/V receivers and A/V controllers.
To see why we need bass management, consider a recording containing full- bandwidth information (low bass as well as midrange and treble) in every channel. A good example is a recording of popular music in which the bass guitar and kick drum are at least partially positioned in the center channel. Most multichannel loudspeaker arrays employ large floorstanding loudspeakers in the left and right positions, and smaller speakers in the center and rear positions. Low frequencies from the bass guitar and kick drum would overload the small center speaker, introducing distortion or dam aging the speaker. Bass management selectively filters bass from certain channels you specify according to the kind of loudspeakers in your system. That low bass can be directed to a subwoofer, if your system includes one.
If you’ve set up a home-theater receiver or controller and selected LARGE or SMALL from the menu for each of your speakers, you’ve worked with bass management. The SMALL, setting simply engages a high-pass (low-cut) filter on that channel, preventing low bass from reaching the speaker. A typical cutoff frequency is 80Hz.
Bass management in the DVD-A format is performed via on-screen menus. SACD players typically have a selection of common loudspeaker configurations from which to choose; you simply engage one from the player’s front panel with no need for a video display. For example, setting #1 may be ideal for a system with large left and right speakers, small center and surround speakers, and a subwoofer.
The bass-management set-up controls are sometimes accompanied by a variable delay to each channel. You set the amount of delay according to how far you sit from each loudspeaker so that the sound from each speaker reaches you simultaneously. For example, if you sit 12’ from the left and right speakers, but only 6’ from the rear speakers, six milliseconds (6ms) of delay to the rear speakers result in coincident arrival of front sounds with those from the rear. (Sound travels at roughly one foot per millisecond.)
The Future of High-Resolution Digital Audio
Unfortunately, we may never see a consumer format that delivers high-res audio and a huge library of tides. The reason is that record companies believe consumers are satisfied with CD sound, and even with the inferior sound quality of MP3 and other highly compressed formats. The mass acceptance of MP3 bears this out, although many of us care about music and the quality of its reproduction.
Nonetheless, the two formats that are now vying to replace DVD as the high- definition video replacement for the DVD offer the provision for audio-only configurations that can deliver very high-quality stereo or multichannel digital audio.
The first of these formats, HD DVD, has an audio-only form in which it can store up to eight channels of digital audio with sampling rates up to 96kHz and word lengths of up to 24-bits. In 2-channel mode, the sampling rate can be increased up to 192kHz. The rival Blu-ray Disc also can serve as an audio-only carrier, with up to eight channels encoded at 192kHz sampling frequency and 24-bit resolution. Note that Blu ray has somewhat higher specs due to its greater storage capacity (25GB per layer for Blu-ray vs. 15GB per layer for HD DVD). Whether either or both of these formats becomes a high-resolution music carrier remains to be seen.
What is not in doubt is that we will see concert videos and musical performances on these formats accompanied by uncompressed, high-resolution audio. As mentioned earlier, the Dolby TrueHD format delivers high-resolution multichannel audio to accompany the video with perfect bit-for-bit accuracy to the source. The competing DTS system also offers a lossless high-res delivery format called DTS-HD Master Audio. Both Dolby TrueHD and DTS-HD Master Audio are options to the disc producers, not requirements of the HD DVD and Blu-ray Disc formats. ( Section 10 has a more in-depth discussion of these newer surround-sound formats and their application to home theater.)
Music Servers
An entirely new product category called the music server made its introduction in 2002. This digital-audio recording device employs large hard-disk drives to store hundreds of hours of music, usually recorded from CD. Transferring your CD library to a single computer-based device confers many advantages, including instant access to any piece of music without searching through CDs; no need to open a CD and insert it into a player; no CD-storage problems or clutter; and the ability to create custom music playlists by genre or group. You could, for example, tell the server to play two hours of a particular artist, or six hours of classic jazz, or three hours of chamber music. The digital-audio server opens up new possibilities for the way in which we access our music. Incidentally, Apple’s iPod is essentially a music server that happens to be portable and also contains a miniature stereo system.
A music server can store a large music library on its integral hard-disk drives, and provides instant access to any selection.
Music servers may be operated through an on-screen graphic user interface.
Audio can he stored on the server’s hard drives uncompressed (consuming about 10.5MB per stereo minute or with a compression scheme that increases a given drive’s storage capacity at the expense of sound quality. Compression systems are avail able that result in about a 2:1 reduction in the storage requirement, but don’t degrade sound quality—they achieve perfect bit-for-bit accuracy to the source.
Some servers have fixed hard-drive capacity, with no provision for expansion if you need more storage space. Others allow you to add additional drives as your music collection grows. A few also provide the option of removable drives so that you can back-up your music. This requires copying the data from one drive to another, removing one of the drives, and putting it away in case of a drive crash. Others simply store the audio data on two separate drives. As anyone who’s used a personal computer knows, the hard-disk drive is the least reliable component, and prone to sudden and catastrophic failure. If this happens to the drives in your server, you’ll need to rerecord (and re-classify) all of your CDs, unless you have a server with the removable backup option. If you choose to commit your music library to a digital-audio server, I strongly recommend keeping the original CDs in case of a drive crash.
Computer-Based Digital Audio and File Formats
The personal computer has revolutionized how a new generation of music listeners accesses and enjoys music. The ability to download virtually any piece of music with a few keystrokes and mouse-clicks has been both a blessing and a curse. Although easy access to a wide variety of music is generally a good thing, downloaded music is severely compromised in sound quality. The popular MP3 format, for example, encodes music with perhaps one-tenth the data rate of CD, and one-fiftieth the data rate of a high-resolution format such as DVD-Audio. MP3 and other such “lossy” compression formats were designed for convenience and low transmission and storage requirements, not sound quality. Sadly, many young people today have never heard their favorite music via an uncompressed format.
Not all computer-based audio is low-resolution; the Music Giants download service offers high-resolution downloads. Many portable audio players that rely on a computer, such as Apple’s iPod, have the ability to store uncompressed music, or music using a lossless compression system.
The iPod can be part of a high-end audio system provided that you also have a CD player for loading music onto it (as opposed to downloading music) and that you store the music using either WAV files or Apple Lossless encoding. WAV files are identical to the source data on the CD; there is no loss in fidelity. The downside is that WAV files consume lots of disk-storage space (about 10.5MB per stereo minute). A better alternative is Apple Lossless, an encoding scheme that cuts in half the storage requirements with no loss in sound quality. The digital bits that come out of Apple Lossless are identical to those that went in.
Using an iPod or other portable music player as a source in a high-end system gives you instant access to your favorite music, and in effect functions as a music server. The downside is that the sound quality is compromised by the portable player’s digital-to-analog conversion circuitry, as well as the quality of its analog output electronics. The iPod is, however, surprisingly good sounding, and is a great choice for budget systems or for programming background music.
How to Choose a Digital Source
When choosing a digital source, you must first decide what formats you will be listening to. If CDs will be your primary digital source, choose a dedicated CD player or a multi-format machine with good CD playback quality. If you’d like to experience high-resolution multichannel music (and have a multichannel playback system), select a player with those capabilities.
If your system is based on an A/V controller or A/V receiver rather than an analog preamplifier, digital-to-analog (D/A) conversion can be performed in the controller or receiver rather than in the player. You simply connect a digital cable between the player and controller or receiver, bypassing the player’s digital-to-analog conversion circuitry. This technique replaces the D/A conversion in the player with the D/A con version inherent in all controllers and receivers. The quality of the audio section in the source player (probably a DVD machine) no longer has an effect on the sound quality Instead, the D/A conversion circuitry in the controller or receiver determines the quality of the sound from digital sources.
What to Listen For
Perhaps more than any other components, digital sources come in the most “flavors.” That is, their sonic and musical characteristics vary greatly between brands and models. This variability has its drawbacks (“Which one is right?”), but also offers the music lover the chance to select one that best complements her playback system’s characteristics and suits her musical tastes. The different types of musical presentations heard in CD players, SACD machines, DVD-A players, transports, and digital processors tend to reflect their designers’ musical priorities. If the designer’s parts budget—or skill—is limited, certain areas of musical reproduction will be poorer than others. The trick is to find the processor that, in the context of jour system, excels in the areas you find most important musically.
Selecting a digital source specifically tailored for the rest of your playback system can sometimes counteract some of the playback system’s shortcomings. For example, don’t choose a bright-sounding CD player for a system that is already on the bright side of reality Instead, you may want to select a player whose main attribute is a smooth, unfatiguing treble. Each digital product has its particular strengths and weak nesses. Only by careful auditioning—preferably in your own system—can you choose the product best for you.
To illustrate this, we’ve invented two hypothetical listeners with different systems and tastes—and two hypothetical CD players we’ve used a CD player in the example, but CD transports, digital processors, SACD, or DVD-A machines could be easily substituted. Although the following discussion could apply to all audio components, it is particularly true of digital components. Not only are there wide variations in sonic characteristics between processors, but a poor-sounding digital processor at the front-end of a superb system will ruin the overall performance.
Listener A likes classical music, particularly early music, Baroque, and choral performances. She rarely listens to full-scale orchestral works, and never plays rock, jazz, or pop. Her system uses inexpensive solid-state electronics and fairly bright loudspeakers; the combination gives her a detailed, forward, and somewhat aggressive treble.
Listener B wouldn’t know a cello from a clarinet, preferring instead electric blues, rock, and pop. He likes to feel the power of a kickdrum and bass guitar working together to drive the rhythm. His system is a little soft in the treble, and not as dynamic as he’d like.
No let’s look at the sonic differences between two inexpensive and similarly priced CD players and see how each would—or wouldn’t—fit in the two systems.
CD player #1 has terrific bass: tight, deep, driving, and rhythmically exciting. Unfortunately, its treble is a little etched, grainy, and overly prominent. CD player #2’s best characteristics are its sweet, silky-smooth treble. The player has a complete lack of hardness, grain, etch, and fatigue. Its weakness, however, is a soft bass and limited dynamics. It doesn’t have a driving punch and dynamic impact on drums compared to CD player #1.
I think you can guess which player would be best for each system and listener. CD player #1 would only exacerbate the brightness Listener A’s system already has. Moreover, the additional grain would be more objectionable on violins and voices. CD player #2, however, would tend to soften the treble presentation in Listener A’s system, providing much-needed relief from its relentless treble. Moreover, the sonic qualities of CD player #1—dynamics and tight bass—are less important musically to Listener A.
Conversely, Listener B would be better off with CD player #1. Not only would player #1’s better dynamics and tighter bass better serve the kind of music Listener B prefers, but his system could use a little more sparkle in the treble and punch in the bass.
Which CD player is “better”? Ask Listener A after she’s auditioned both products in her system; she’ll think player #2 is greatly superior, and wonder how anyone could like player #1. But Listener B will find her choice lacking rhythmic power treble detail, and dynamic impact. To him, there’s no comparison: player #1 is the better product.
Though exaggerated for clarity, this example shows how personal taste, musical preference, and system matching can greatly influence which digital products are best for you. The only way to make the right purchasing decision is to audition the products for yourself. Use product reviews in magazines to narrow your choice of what to audition. Read reviewers’ descriptions of a particular product and see if the type of sonic presentation described is what you’re looking for. But don’t buy a product solely on the basis of a product review—a reviewer’s system and musical tastes may be very different from yours. You could be Listener A and be reading a review written by someone with Listener B’s system and tastes.
Use reviews as guides in pointing you to products you might want to audition yourself not as absolute truth. You’re going to spend many hours with your decision, so listen carefully before you buy—it’s well worth the investment in time. Moreover, the more products you evaluate and the more careful your listening, the sharper your listening skills will become.
It’s important to realize that the specific sonic signatures described in the example are much more pronounced at lower price levels. Two “perfect” digital play back devices would sound identical. At the very highest levels of digital playback, the sonic tradeoffs are much less acute—the best products have very few shortcomings, making them ideal for all types of music.
Still, a significant factor in how good any CD player sounds is the designer’s technical skill and musical sensitivity. Given the same parts, two designers of different talents will produce two very different-sounding products. Consequently, it’s possible to find skillfully designed but inexpensive products that outperform more expensive products from less talented designers.
Higher-priced products are not necessarily better. Don’t get stuck in a specific budget and audition products only within a narrow price range. If an inexpensive product has received a rave review from a reviewer you’ve grown to trust, and the sonic description matches your taste, audition it—you could save yourself a lot of money. If you decide not to buy the product, at least you’ve added to your listening database, and can compare your impressions with those of the reviewer.
In addition to determining which digital products let you enjoy music more, there are specific sonic attributes you should listen for that contribute to a good-sounding digital front-end. How high a priority you place on each of these characteristics is a matter of personal taste.
In the following sections, we’ve outlined the musical and sonic qualities I look for in digital playback.
The first quality we listen for in characterizing how a digital component sounds is its overall perspective. Is it laid-back, smooth, and unaggressive? Or is it forward, bright, and “in my face”? Does the product make me want to “lean into” the music and “open my ears” wider to hear the music’s subtlety? Or do my ears tense up and try to shut out some of the sound? Am I relaxed or agitated?
A digital product’s overall perspective is a fundamental characteristic that defines that product’s ability to provide long-term musical satisfaction. If you feel assaulted by the music, you’ll tend to listen less often and for shorter sessions. If the product’s fundamental musical perspective is flawed, it doesn’t matter what else it does right.
Keywords in product reviews that describe an easy-to-listen-to digital product include ease, smooth, laid-back, sweet, polite, and unaggressive. Descriptions of bright; vivid etched aggressive, analytical, immediate, and incisive all point toward the opposite type of presentation.
There is a fundamental conflict between these extremes of presentation. Processors that arc smooth, laid-back, and polite may not actively offend, but they often lack detail and resolution. An absence of aggressiveness is often achieved at the expense of obscuring low-level musical information. This missing musical information could be the inner detail in an instrument’s timbre that makes the instrument sound more lifelike. It could be the sharp transient attack of percussion instruments; a slight rounding of the attack gives the impression of smoothness but doesn’t accurately con vey the sound’s dynamic structure. Consequently, very smooth-sounding digital products often have lower resolution than more forward ones.
The other extreme is the digital product that is “ruthlessly revealing” of the music’s every detail. Rather than smoothing transients, these products hype them. In a side-by-side comparison, a ruthlessly revealing product will appear to present much more detail and musical information. It will sound more upbeat and exciting, and will appeal to some listeners. Such a presentation, however, quickly becomes fatiguing. The listener feels a sense of relief when the music is turned down—or off The worst thing a product can do is make you want to turn down the volume, or stop listening altogether.
Digital reproduction also has a tendency to homogenize individual instruments within the soundstage. This tendency to blur the distinctions between individual instruments occurs on two levels: the instruments’ unique timbral signatures and specific locations within the soundstage.
On the first level, digital products can overlay music with a common synthetic character that diffuses the unique textures of different instruments and buries the subtle tonal differences between them—the music sounds as if it is being played by one big instrument rather than many individual ones. Instead of separate and distinct objects (instruments and voices) hanging in three-dimensional space, the listener hears a synthetic continuum of sound. There is a “sameness” to instrumental textures that prevents their individual characteristics from being heard.
The second way in which digital playback can diffuse the separateness of individual instruments is by presenting images as flat “cardboard cutouts” pasted on top of each other. The instruments aren’t surrounded by an envelope of air and space, the soundstage is flat and congested, and you can’t clearly hear where one image ends and the next begins. Good digital playback should present a collection of individual images hanging in three- dimensional space, with the unique tonal colors of each instrument intact and a sense of space and air between the instrumental images. This is easy for analog to accomplish, but quite difficult for digital. A recording with an excellent portrayal of timbre and space will help you identify which digital products preserve these characteristics.
Beyond these specifics, a good question to ask yourself is, “How long can I listen without wanting to turn the music down—or off?” Conversely, the desire—or even compulsion—to bring out CD after CD is the sign of a good digital front-end. Some components just won’t let you turn off your system; others make you want to do something else.
This ability to musically engage the listener is the essence of high-end audio. It should be the highest criterion when judging digital front-ends.