INTRO: Pick up an audiophile magazine in 2011 and you’re likely to find reviews of equipment for playing vinyl LP’s dating back to the 1940’s and the Compact Disc from the early 1980’s. In the last 25+ years, much has changed. So why do many hardcore audiophiles still cling to ancient formats? I’ll leave the Great Vinyl Debate for another article, but what’s the best digital format for audio playback? CD? SACD? FLAC? Apple? Dolby TrueHD?
COMPACT DISCS: I don’t have anything against CDs--I own about 6000 of them. All but a few, however, are safely packed away (mostly to keep the RIAA happy should they ever knock on my door). And the few that are readily accessible are either awaiting their turn to be ripped or used for for test purposes. Digital music files became my primary source 8 years ago when FLAC lossless compression was released.
THE LAST OF THE DINOSAURS: While players that only play CDs have all but disappeared from mainstream stores, there are still lots of audiophile offerings and even some new models. Granted there are lots of CDs in circulation, but increasingly, few are playing them anymore. They were ripped on a computer long ago and boxed up in a closet or sold. And the ones sold often get ripped and sold again. It’s no wonder CD sales have tanked. But, oddly, audiophiles seem way more likely to still play their actual CDs.
WHY DO AUDIOPHILES KEEP PLAYING CDs? It’s work to store, organize, play, put away, and generally pamper those little silver discs. If so many people are still doing it, they must have some good reasons, right? Let’s look a half dozen of the reasons:
- SOUND QUALITY: Many audiophiles still fussing with little silver discs will tell you it’s because they sound better than other forms of digital playback. But hardware has been available for over a decade that’s capable of delivering the exact same bitstream as a CD transport to the same expensive audiophile-approved DACs. Even taking jitter into account, there’s no reason playing a file off a hard drive cannot sound every bit as good as the same data played off a CD transport. A well designed DAC doesn’t care where the bits come from. You can get the exact same analog output from a DAC if they’re played from a CD transport, your PC’s hard drive, or beamed from outer space via satellite.
- LACK OF HIGH-END HARDWARE: While the choices were slim many years ago they’re fairly plentiful today. There a probably hundreds of DACs, from $30 to $30,000, that have USB jacks on them and can connect to any computer—PC or Mac. There are also a lot of network music and media players including several from high-end companies. And there are countless iPod docks including many high-end ones.
- COMPRESSION SOUNDS BAD: Lossy compression such as MP3 and AAC has often been done poorly, at substandard bitrates, etc. And this has generally given all compression a bad name among many audiophiles. But you don’t have to use any compression. And, as I’ll explain later, lossless compression delivers identical sound to playing a CD. So, in terms of sound quality, there’s no reason not to use it.
- DATA STORAGE IS A PROBLEM: Back in 1983, when the first CDs were sold, the amount of data on a single CD would have required 65 10 MB hard drives at a cost of around $120,000.00 to store the raw data! Today, you can put 3000 bit-accurate lossless CDs on a 1 Terabyte hard drive ($50) at a cost of $0.02 each. You can also get an inexpensive NAS—Network Attached Storage device that sits on your network using little power ready to serve up your music anytime.
- DATA (MUSIC) LOSS: When hard drives are around $50 and two cents per CD, it’s fairly trivial to make a couple redundant backups to store off site and then even if your house burns down your music is safe. That old CD collection, however, will be toast. There are also fireproof, shockproof and waterproof external drives like those from ioSafe—with or without redundancy. And there are variety of NAS units with redundancy. And most of this hardware costs significantly less than an audiophile approved CD player.
- TOO MUCH WORK: Granted ripping a large CD collection to a hard drive is time consuming. But with lossless compression, you can easily pay someone else to do it without having to worry about the quality of the result. There are many commercial services that specialize in CD ripping. And, regardless, it’s a one time effort that pays off in less work every time you play music compared to the hassle of CDs. You can instantly find and play anything in your collection, build playlists of anything you want, enjoy playback volume leveling, and much more. You never have to find, and put away, a CD again.
OTHER REASONS? Am I missing any other reasons, besides perhaps being nostalgic or a luddite, to keep using CDs?
DIGITAL FORMATS: I couldn’t find more recent numbers, but when the open freedb CD database was cleaned of duplicates in 2006 it had approximately 2 million unique CD titles. The CDDB/Gracenote database is supposedly much larger but apparently Sony (the current owner) doesn’t publish the data. It’s probably not a stretch to say there are 3+ million CD titles in circulation. And by 2007, over 200 billion CDs had been sold. So how does that measure up to other formats?
- 99.7% CD 16 bit 44.1 khz 3 million titles
- 0.2% SACD DSD 1 bit High Resolution 6500 titles (mostly classical/jazz)
- 0.06% DVD-Audio Up To 24 bit 192 Khz 1800 titles (mostly classical/jazz)
- 0.03% Hi-Res Downloads 24 bit 88/96 Khz 1000? (mostly classical/jazz)
So, 99.7% of the digital music commonly available is 16 bit 44 khz CD quality audio (or compressed versions of the same). If your goal is to listen to music, rather than equipment, there’s essentially only one native format right now as nothing else has really caught on.
HIGH RESOLUTION DISC FORMATS: Many smart people have demonstrated CD quality audio is sufficiently transparent for high quality music playback. SACD, as you can see above, has been the most successful of the hi-res formats—if you can call 0.2% “successful”. Meyer and Moran, in 2007 conducted a year long study with over 500 trials using audiophiles, recording engineers and students, and none of them, under normal listening conditions, were able to reliably tell when they were listening to an SACD or a CD quality 16/44 version. Even to the golden eared listeners, CD quality audio and SACD hi-res audio sounded the same. Sales volumes have been so low SACD was declared a “complete failure” in 2008. Considering SACD was originally trying to fix a problem that didn’t really exist, it’s easy to understand why it failed. Meyer and Moran, naturally, were largely attacked by the audiophile community. I discuss the study more in my Subjective vs Objective article.
THE MASTERING MYTH: I know many who compare a 2 channel SACD to the CD of the same title and plainly hear a difference. And there often is a real difference that survives a blind listening test. But, as Meyer and Moran demonstrated, it’s very likely not from the format, but from the SACD being mastered differently. There’s very little SACD content that’s not been altered when re-mastered for SACD. So it’s not a fair comparison.
HIGH RESOLUTION PART TWO: If you’re still convinced hi-res formats sound better, first I would suggest reading my Subjective vs Objective article providing lots of evidence we humans hear things that don’t exist. And there are many threads at Hydrogenaudio on the subject. There have been several trials where the free Foobar 2000 software player with ABX was used for blind comparisons of the same track in high res and CD formats using high quality 24/96 playback hardware. And, almost without fail, nobody can tell the difference. One AES study on sampling rate found some extremely slight differences that only a few of the listeners could hear and only with one piece of music. This study is discussed in a Hydrogenaudio thread.
HIGH RESOLUTION RECORDING FORMATS: When it comes to recording, hi-res formats, like 24/96 PCM and DSD, are clearly the way to go. Unlike with digital audio playback, there’s little dispute hi res allows for greater dynamic range and less degradation during editing. But, for playback on the consumer side of things, any benefits of hi-res are much less obvious and, at best, extremely subtle.
LOSSY COMPRESSION: This could be a topic by itself. Even audiophiles, in blind tests with high end gear, usually can’t tell lossy compressed audio (i.e. MP3, AAC, etc.) from the uncompressed version when it’s been properly encoded. But much of the compressed audio we listen to wasn’t properly encoded—including much of what’s available from iTunes, Amazon, etc. A lot of it has been encoded and/or transcoded in ways that optimize processing speed over audio quality. And, worse, some of it has been through more than one lossy operation. So audiophiles have some justification in their dislike of lossy compression. Typical high quality lossy compression is around one fifth the size of the original making storage on portable devices and streaming much easier. It’s too bad it hasn’t been used more carefully.
LOSSLESS COMPRESSION: FLAC and Apple Lossless are the two most popular lossless compression formats and quite a bit newer than MP3. They perform the same but FLAC is much more widely implemented than Apple’s in-house format. So FLAC provides vastly more playback options. The advantage of lossless is it really is lossless. The bits you end up with are the exact same bits in the uncompressed version. Audiophiles are finally starting to come around, but for a long time many thought any compression, including lossless, sounded worse. Ultimately, the DAC can’t tell the difference.
CONSUMER DEMAND: The masses are the 800 pound gorilla. So far, there hasn’t been much demand for higher quality audio formats. In fact, as demonstrated by the huge success of iTunes alone, the vast majority are not only happy with CD quality, but lossy compressed versions that often sound worse. Those who grew up listening to iPods have even expressed a preference for the sound of lossy compression. It’s what they’re used to, so for them, that’s what music is supposed to sound like. This doesn’t bode well for the future unless preferences change or the barriers to higher quality formats, most notably network speeds, bandwidth and copyright concerns, are greatly reduced.
DIGITAL INTERFACES & BITSTREAMS: From a strictly theoretical point of view, any interface with enough bandwidth can move digital audio around. From a practical perspective there are some differences. Here are most of the possibilities:
- Self Contained Playback (I2S) – When you use use a CD player, iPod, or PC as a self contained playback device the digital audio bitstream never leaves the device. You get an analog output and all the bits are handled internally. In reality there is an internal digital audio interface, and the input to the DAC itself likely uses the I2S interface. I2S has the advantage of keeping the clock and the data separate so there’s no issue of “clock recovery” but it’s still prone to being implemented poorly. Because the storage format doesn’t matter, it’s entirely possible to design an iPod-like device that performs as well as a high-end CD player or even better.
- Ethernet/WiFi/Internet/3G/Etc. – When you “stream” audio over a network you can still get “bit perfect” data at the receiving end. Networks have very robust protocols that prevent errors. Software applications can crash if even a single bit is corrupted. Digital music, by comparison, is a walk in the park as long as there’s sufficient bandwidth to do it in real time. Contrary to myth, networks don’t create jitter, reduce the soundstage width, or remove the “air” from around Yo-Yo Ma’s cello. From the DAC’s perspective, the reassembled audio looks exactly the same as if it had come off a local hard drive, CD, or from flash memory. There are only two potential problem areas with network streaming:
- Real Time Dropouts – Ever watch a YouTube video and had it pause during playback? That’s because there’s a bottle neck somewhere between you and YouTube’s servers that restricted the bandwidth to less than required for real time video. Fortunately audio usually needs less bandwidth than video, but the same thing can still happen—especially with WiFi or mobile connections with high quality audio. This isn’t some subtle audiophile quality issue, the audio will just stop playing nearly always in obvious ways. Larger buffers help prevent dropouts.
- Real Time Synchronization – Generally this is a non-issue. For network audio playback there’s typically some delay in the audio as it’s buffered locally by whatever is playing it. You don’t care if the bits are leaving the source a half second earlier than when the sound reaches your ears. But if you’re trying to play the same internet radio station in two rooms of your apartment using two different players, now you have a potential problem. With analog FM radio this worked great. With digital you’ll likely have an echo between the two rooms due to different buffering delays. This is not a sound quality problem and you would also have a hard time trying to play the same CD in perfect sync in two different rooms on two different players. There are network players that address this issue (i.e. Sonos).
- Optical (TOSLINK) & Coaxial S/PDIF – This interface has been maligned by audiophiles—primarily because the digital bit clock is embedded with the data and must be recovered at the other end. The professional AES3 (also called AES/EBU) digital interface gets much more respect. What some may not realize is they’re essentially the same standards. AES3 just uses a balanced 3 pin XLR connector. TOSLINK, coaxial S/PDIF and AES3 all embed the clock and move data in the same way. The vast majority of the music we listen to, even some on vinyl, has already been through the AES3 interface. So if embedding the clock corrupts the sound quality, consider most of your music already corrupted. S/PDIF was developed by Sony and Philips (the S/P) as a consumer version of AES3 with the introduction of the MiniDisc to allow recording digital sources. Likely because some CD players started including S/PDIF outputs the audiophile industry started using it between high-end CD transports and separate DACs. These interfaces—especially with long cable lengths--can contribute to jitter.
- AES3 (AES/EBU) – This is the professional version of S/PDIF and in most applications the two interfaces perform about the same as they essentially are the same. The advantage of AES3 is it can be sent over longer cable distances with less degradation than S/PDIF due to the balanced cable. And that can reduce jitter in some circumstances.
- Firewire – In the mid 90’s it became practical to record, edit and master digital audio on a PC instead of an expensive dedicated Digital Audio Workstation. Around that time the IEEE 1394 “Firewire” interface was popularized by Apple. Even though Firewire predates, just barely, USB it never really caught on in a big way outside of a few limited niches. One such niche is professional audio. USB has finally caught up, but for many years if you wanted to move more than two channels of high quality audio in and out of a PC, Firewire was the preferred way of doing it. But it appears to be a dying technology just like the ill fated Apple Desktop Bus before it. Apple has now gone out on a limb with Thunderbolt and many have suggested Thunderbolt and USB 3.0 will be the demise of Firewire. In any event, it’s use in audio has mainly been limited to professional, not audiophile, gear.
- USB – Along with network streaming, USB is one of the most popular consumer digital audio interfaces. Prior to 1998 you generally had to install proprietary drivers to interface a computer to a USB audio device. But in 1998 the USB standards group published the USB Class Definition for Audio Devices (PDF). The new standard allowed native support of USB devices within operating systems including Windows, OS X, and Linux. USB audio then gave new meaning to “plug-and-play”. For more than a decade it’s been possible to plug a high quality external DAC into just about any PC and it magically Just Works. So, it’s all the more puzzling there are so many people still messing with little silver discs. But there are a few more things worth knowing about USB Audio:
- USB Jitter? – There’s been a lot of talk about “asynchronous” USB DACs and various jitter issues with the USB interface. Part of the issue is that most USB DACs, unlike network players, don’t have a real digital audio buffer. Instead, the buffering is done in the operating system at the driver level in the PC. So the data is being streamed, more or less, in real time over the USB cable. Any jitter, however, is a function of the USB hardware within the DAC or other audio device as USB packets of data are completely different than a digital audio audio datastream. It’s the conversion process that’s tricky but the important thing to know is it’s an entirely different data format that either works or it doesn’t. USB problems are rarely subtle. For more details, see my jitter article.
- USB Hi Res is Rare - There are only a few USB chips that can handle anything above 16/48 and some of them are difficult or costly (in licensing fees) to implement. As long as that’s true, the majority of USB audio devices, despite often having DAC chips that can do 24/96 or 24/192, can only operate up to 16/48 via USB. So be careful when shopping if you’re expecting hi res audio via USB. Some other devices, like the popular E-Mu 0202 and 0404 require proprietary drivers that can be problematic.
- USB Cable Myth – There are now lots of “audiophile” USB cables but USB (and HDMI) data transmission either works or it doesn’t. When it doesn’t the results are generally obvious in the form of ticks, pops, dropouts, errors from your computer, the device locking up, etc. The cable doesn’t create jitter so a better cable can’t have less jitter, enhance the sound stage, or otherwise work any subtle magic on the sound quality.
- USB Audio 1.x – This is the original 1998 standard and supports up to 24/96 two channel stereo audio in one direction (either recording OR playback but not both at once). It uses the USB 1.x Full Speed (12 Mbit) interface and uses less than 5 Mbits of bandwidth. It’s capable of flawless high quality audio as demonstrated by golden-ear approved products such as the Benchmark DAC1 and Grace Designs m903. This is sometimes known as “Class 1 USB Audio”.
- USB Audio 2.0 – This was introduced in early 2009 and has been adopted by a few manufactures—mostly in pro audio so far. This “Class 2” interface uses the much faster 480 Mbit USB 2.0 standard and allows for 24/192 multi channel audio in both directions simultaneously. The few audiophile companies who have adopted 24/192 Class 2 have found it to be a can of worms. Ayre, for example, specifies never using USB hubs, keeping the USB cable to 3 feet or less, not sharing the USB interface with any other devices, and warns that not all PC’s and USB hardware will work correctly. Unless you’re doing multi-track recording, all this is rather unimportant as Class 1 24/96 is all anyone needs (Meyer and Moran have shown 16/44 playback is sufficiently transparent 99.9% of the time and 24/96 is overkill).
- Internal PC Slots – Some still advocate putting a high quality sound card, like the Asus Xonar ST/STX, inside your PC in a PCI slot. But this is flawed in many ways including a much more electrically noisy environment, slots inside PCs are going away, and it generally requires proprietary drivers that are often buggy. Like CDs, it’s a very 1980s solution. I suspect the Xonar ST and STX are among the last of the audiophile-grade 2 channel sound card dinosaurs.
- HDMI – Increasingly HDMI is being used to move digital audio as well as video. It supports many formats including plain old PCM 16/44 CD quality. And, like USB, the quality of the implementation is typically the limiting factor, not the cable or standard itself. The main advantage of HDMI is ease of use for A/V gear and it supports multi channel digital audio formats including SACD’s DSD, Dolby TrueHD and DTS-HD Master Audio—all of which are lossless. A modern Blu-Ray player can send many high quality audio formats directly to an A/V receiver or A/V processor/preamp.
- Other Options – Some recording studios use externally clocked AES3 with a single central high-end clock. In this case a completely different cable carries the clock. This is generally used where multiple digital devices are best operated in sync with each other as with multitrack live recording for example. This generally isn’t applicable to home playback. As mentioned above, USB 3.0 and Thunderbolt will likely be used someday for audio but most likely for recording.
JITTER: I wrote an entire article on jitter but it’s sufficient to say it can be an audible problem. I’m not sure how often it actually is audible, but it seems reasonable to try and minimize it. Which brings me to my next point.
THE MULTI BOX MYTH: Audiophiles seem obsessed with dividing up the functionality of their systems. Some have a tuner, phono pre-amp, general pre-amp and one or more power amps instead of a receiver. Like many audiophile myths, this has the strong potential to make things worse rather than better. The “two box” CD player is a perfect example. There’s nothing about a CD transport that’s incompatible with having a DAC in the same device. Yet audiophiles seem to think splitting them apart makes for better sound. It usually requires sending audio through the very S/PDIF interface they don’t like. S/PDIF embeds and reconstructs the clock creating potential jitter. This also applies to network media players, external DACs for iPods, and USB-to-S/PDIF boxes. In general, it’s better to have one engineer (or team) responsible for as much of the playback chain as possible. That way you can be assured everything is designed to play nice together. And, more important, everything can run from one clock which can greatly improve jitter. In the headphone world, a self contained headphone DAC (one box) has the potential to perform much better than a USB-to-S/PDIF box connected to a DAC connected to a headphone amp (three boxes). But the more audiophiles spend in their pursuit of audio nirvana, the more likely they use multi-box configurations. Perhaps they would also prefer a car with the engine in a trailer?
HIGH RESOLUTION PART 3: Now that storage is cheap, and the Internet hasn’t yet been crushed under YouTube, Netflix and Spam, I suspect we’ll gradually see more hi-res audio. Apple has strongly hinted they’re working towards offering 24 bit downloads in their iTunes store. I’m all for Apple improving the quality of their music offerings, but that’s often more about what’s behind the scenes—lossy compression, transcoding and improper sample rate conversion—than bit depth. For the consumer, especially playing music on an iPod, 16 bits is plenty. What Apple 24 bit audio is really about is more profit for Apple. It would provide incentive for people to buy new Apple hardware with 24 bit support, and “upgrade” their music by re-buying it in the new format. It also could, no doubt, help swing many audiophiles into buying from iTunes rather than elsewhere. So it’s a great marketing move, and if it’s lossless, it might mean slightly better sound compared to lossy AAC. But lossless 24 bit files are comparatively huge. And, to do it right, they have to start from scratch with the original studio masters. So there are some serious hurdles.
MULTI CHANNEL: Multi channel audio, without video, has never really caught on. Most of the SACDs sold are multi-channel remixes of popular CDs. And, on a system optimized for multi channel music (versus movie) playback, some offer a very immersive and impressive sound. But not enough consumers cared for SACD (or the similar DVD-Audio) to ever get any real traction. I think part of the problem is a lot of music listening is either done casually around the home rather than sitting in the sweet spot. And many others listen with 2 channel headphones. Plus multi channel systems optimized for home theater are rarely ideal for multi channel audio. For movies you want a diffuse rear sound field and audio is usually mixed assuming a focused rear sound field. And now we have Dolby TrueHD and DTS-HD Master Audio--both of which support lossless multi channel audio and pound more nails into the SACD coffin. Many Blu-Ray players can output both via HDMI. With downloads replacing physical media it will be easier, at least in theory, to distribute multi channel audio in the future. The trick will be playing it how you want, not how say Apple wants you to.
DRM: Many consider DRM (Digital Rights Management) a bad thing. It’s basically copy protection and it does get in the way. But it also allows for some fairly amazing things like inexpensive subscription streaming music plans from Napster, Rhapsody, Spotify, etc. For around $10/month you can have access to a giant catalog of music with millions of tracks. Sure it might be in a lossy format, but much of it sounds relatively good. For those who haven’t tried it, it’s rather addictive to be able to listen to most anything, legally, anytime, with just a couple clicks or taps. Without DRM, it wouldn’t exist. There’s usually a way around most DRM but sometimes it’s not very practical, or convenient, and it’s usually illegal. So I see DRM as a worthwhile evil.
THE FUTURE: Two channel audio is pretty well covered in terms of formats. There are a few sources for lossless downloads, like HD Tracks, where the labels have agreed to it. But, much like SACD, the catalog of titles is so far very limited. The right DRM would help free up the log jamb as more music labels would then sign on but that will likely limit playback options. Apple’s 24 bit could be such a DRM format. Downloadable Dolby TrueHD and/or DTS-HD Master Audio multi channel lossless audio are also possibilities but there’s the same DRM issue. I can imagine a future where it’s easy to buy lots of high quality lossless music online in downloadable formats. But I bet only a minority will be DRM free. The rest will likely be restricted to authorized playback devices. Such devices will likely have a closed, self contained, architecture to prevent easy removal of the DRM. Apple, with their relatively closed proprietary world, is in a perfect position to blaze the trail. And, if that works out, we might get lucky and others will follow. But it will only be happen if there’s enough money to be made. And so far, the track record on that isn’t good. But if anyone will pony up for supposed higher quality, it will be Apple’s demographic. In the meantime, if you’re still fooling around with silver bits of plastic, consider an upgrade to 21st century technology.
MORE INFO: The Well Tempered Computer site has a lot of good information if you’re new to computer audio.