Let’s be honest: the smartest thing to do today would be ripping all our CD collection on a hard disk (but in a lossless format!), find ourselves a good DAC (digital to analog converter), plugging it in a USB port and let our computer play our favorite music. We would get rid at once of all the issues due to laser beam reading errors and we would improve our music playback. The future, or maybe the present, is the download of musical files, if not the streaming itself. As of now, the most widespread streaming service like Spotify, Apple Music and Google Play, offer good audio quality of compressed music so that the pleasure of listening is quite acceptable. The standard price is 9.99 whether it be euros, dollars or pounds. Tidal offers an high quality music streaming service at double the price (you can also buy and download single files). Still there is somebody who prefers a physical support and does not like the idea of “playing a computer”.
At the moment, despite the ever decreasing sales, the most widespread musical support is the Compact Disc (CD). Years ago it replaced the vinyl record promising a pure and ethernal sound. Actually, this is just what the CD really isn’t. The way the music is recorded on CDs is at the source of its problems. We will talk about it further, but this does not mean that a CD player will not be able to reproduce High Fidelity sound, God forbid! Most of the times, a first HiFi system worth the name will certainly have a CD player at its source (for years I’ve been dreaming about the Meridian CD 506 CD player in the above picture, that I saw very suited to be in my own system…).
Used market – buy safe? Not much…
We must aknowledge that when speaking of digital sources, being that a CD player or a DAC, the differences between models are minimal, even if their prices are not. We’re talking about subtle shades, importanto to some, irrelevant to others. Today we can spend a few money for a good player, used or brand new. Used CD players are more critical than used turntables: the reading mechanism tends to lose the tracking ability with time, leading to a progressive decrease of sound quality. Furthermore, the digital progress makes few years old units obsolete, as it happens with digital cameras. It might be worth noting that in order to obtain the same sound quality of a used 2-300 euro turntable, we should spend up to 1000 for a comparable CD player (like the wonderful Astin Trew AT3500 with valve output stage in the picture at right). Sure, a CD player does not need all the adjustment and tuning a turntable requires, but it is not as long-living and good sounding. And let’s also consider that a modern brand new CD player easily gives a run for its money to a very expensive one from 10 years ago. And it could also happen to be able to play DVDs, like the Oppo player that everybody was talking about some years ago: their video and sound quality at a bargain price have destroyed all direct competitors …and even some more expensive ones. This happens because the yearly advancements of digital technology improve the way of solving the digital recording’s inherent issues of a certain importance. But it is true that a used CD player just a few years old and of good quality (Unison, Arcam, Rotel, Rega, Meridian, Cambridge, Audio Analog, Linn, Naim, etc), could be a more than optimal solution.
Reading unit and D/A converter
Years ago it was advisable to couple a good reading unit with a separate digital-to-analogue converter (DAC). The quality of the integrated CD players of today should discard this possibility, at least when talking about figures lower than 2-3000 euros (the Rega Apollo CD player in the picture at left is damn good and can be found esed at a bargain price). Separates may just be an additional interconnection problem, but they would allow for an easier future upgrade, as well as the possibility to connect several digital sources, cmputer included, to the same DAC. A robust reading unit was considered a must in the past regarding the precision of data extraction from the rapidly spinning CD surface by the laser beam. Not all bits are always recovered. The CD, like the vinyl record, suffers from fluctuations, vibrations triggered by its own rotation as well as by the sound from the loudspeakers. Every player has a circuitry that interpolates the missing data skipped by the laser because of those problems or because of holes, scratches and dirt on the CD surface. The higher the CD player’s quality (and cost), the better its reading system, the less are the missing data, the better is its ability to interpolate them. The more are the interpolated data, the worse is the sound quality. To extract most of the information from a CD, the reading unit had to be impeccable and the player must be placed on a very rigid, isolated horizontal surface. With time, it may be necessary to have the reading assembly tuned up, but it may be not worth the effort, since a new player could be cheaper and better sounding. The DAC unit is the one affected more by the technological absolescence. That’s why it is not advisable to by a used CD player from to many years ago (some exceptions are some real big names). There are different approaces and design phylosophies to turn digital data back to analogue (so they can be amplified). The quality of the converter is the main responsible of the sound quality of a CD player. It is of paramount importance. If we have a separate DAC the good thing is that we can replace it when needed. If we have an integrated player we will have to upgrade the whole thing; if it has a good reading mechanics we can plug it to a new DAC and most certainly improve the sound. Today the issues related to the reading mechanism has a different perspective: the most important thing from the sonic point of view is the DAC; a reading assemblage derived from computer CD-ROMs is good enough (noble players such as the Unison Research Unico CD of the picture above use them in a very profitable way). If the reading mechanism has definitely lost the alignment and it’s not worth to have it repaire, it is better to replace the whole thing taking advantage of the digital technology progress. A cheap DVD player and a good DAC unit could be enough to play both our music files and movies…
MP3 reader? Leave me alone…!
If you’re thinking of using an mp3 reader or similar, keep in mind that the music signal, originally acquired with a lot of approximation so that it can be fit in a CD, it is way more compressed when saved in mp3 format or other lossy formats that are used to store music in flash memory cards. We can bring our entire collection with us, but we lose that part of the music information that may be considered not audible, still it is responsible of that depth, breadth, detail which are the main goal of High Fidelity (certainly attainable with a good CD player). It is also possible with an iPod/iPhone (the are very good sounding) but we should store the whole lossless signal within them, reducing the avilable storage of ten times or so (I’m talking about the WAV format by Microsoft and the AIFF from Apple). The digital signal must be converted to analogue anyway so it can be amplified and played back. The DAC is the heart of a digital system. Unless we plan to use an external D/A converter, the sound performance of an mp3 reader, Apple’s products included, are not comparable to that of a High Fidelity CD player.
Let it be clear that digital recording is simply taking a sample of an analogue signal. Sampling according to the adio CD standard means collecting 44100 samples each second (44.1 KHz). Each sample is assigned a number value corresponding to the amplitude of the analogue wave at that fraction of a second. The CD audio standard uses 16 bit binary numbers to assign amplitude values: an electronic device can only understand “on” and “off”, something we humans represent with “1” and “0” in our binary numeral system (which is based on only two digits instead of 10 like the decimal system). “16 bit” means we have 216 = 65536 digits – different values that can be assigned. It seems a big figure at first glance, but it isn’t. Even if, on each second, we can assign the 44100 samples one of the 65536 values, we will always obtain something like what’s depicted in the diagram at left: a “saw-tooth” signal in place of the original analogue wave. The CD player’s D/A conversion circuits do what thay can to overcome this and other issues of digital audio. The most important is the “jitter”: a normal DAC’s task is to recover each of those 44100 sound samples, assign one of the 65536 amplitude values to each, and place each of them exactly where (in terms of time) they belonged, excactly on the instant the A/D sampler (the digital recorder) did collect them. In a few words, the DAC’s “clock” must be able to synchronize to the clock of the original signal. It never happens, the discrepancy is always there and can just be attenuated, not canceled. This makes a DAC a quality one, the more it is able to reduce jitter (and other typical digital audio issues), the better the DAC performance. Today this is considered much more important that the loss of some interpolatable data. A more radical solution is improve the CD audio sound at the source by elevating the standard. Today, digital audio could take advantage of technologies such as the Super Audio CD (SACD), the DVD Audio or the HDCD, a kind of audio “Blue Ray”. This standards have increased both the sampling frequency and the bit depth of the digital recording process, but none of those standards have really took over. It is hard to imagine now, in the era of Internet and the iPod, a high definition music market that would prompt us to replace our old CDs with a new format as it happened to vinyl records with CDs (like it’s happening with DVD and Blue Ray discs). Now the future is downloading music files, maybe high definition ones: the sampling can be made at 20, 24, 32 bit depth and at 48, 96, 192 KHz. The file sice increases but the audio quality improves. Downloading large files is no big deal today. Once the new optical dic formats are dead, wha tremains is the portable music player …and the computer.
Some might be surpised, but a computer, even a laptop, can be a damn serious digital source in our HiFi systems. Think about it: internal hard disks don’t suffer the same reading precision issues of optical media such as CDs and DVDs. On the contrary, they are way more silent and precise. Your computer’s CD\DVD-Rom player has a very good mechanics. But you’re not supposed to just plug in the computer’s audio output to the amplifier. The right thing to do is ripping digital audio data out of our CD’s to save them in a lossless format (no mp3s!) on the hard disk (better if a fairly-sized external unit) for playback. Today’s external DAC units that can be connected to the USB port make the PC a very nice digital source for our HiFi, maybe the most immediately available for many of us. Since 2007, Apple Macintoshes all have a toslink optical output to connect to an external DAC (you can also use the Firewire port). Just by ripping our CDs into lossless files in the internal disc we can improve the audio performance, especially if the D/A converter withing our CD player in not very good. Simply, hard discs do not vibrate like an optical disc and its magnetic readind system does not lose data like the CD’s laser beam. For further precision and reliability we could think of using modern solid state hard disc (flash memories just like USB pens or memory cards for digital cameras). They radically solve all the issues due to moving masses. It sounds nice to be able to manage all our music collection from our PC. If we also consider the opportunity of downloading high definition musical files up to 192 KHz and 24 bits, the CD standard lags way behind, at least in theory. From several points of view, a computer as digital audio source is probably the most reasonable choice. There is the problem of safely storing an ever growing amount of music files, sam as for digital photos and videos. This could make us wonder whether this is really the most comfortable way. Another consideration to be done is: would a classy, top-rated CD player really be surapssed by a hard disk based system? Maybe some very serious CD players would not show many problems when compared to high definition files playback.
But not all recordings are the same…
Finally, if we really don’t feel like using a PC or if we just cannot do it, a good, few-years old used CD player, carefully selected among the brands named above, can surely give us a lot of HiFi music to enjoy. Even a modern DVD/Blue Ray multi-format player particularly focused on audio quality like those from Oppo or Cambridge Audio, can be a reasonable choice (we would also satisfy our cinematographic needs). Spotify, Apple Music and Google Play can offer most of the existing music for 10 bucks a month. It makes you wonder who would possibly still buy CDs or vinyl records.
But not all recordings, even from famous artists, no matter if on CD or vinyl, are made the same. Unfortunately, it is not uncommon to stumble upon recordings (even modern vinyl issues) produced according to a kind of fashion that has been spreading in the music industry in the recent years (unbelievably, with the agreement of some musicians!): an ever growing compression of the music signal.
A musical piece is made of different sections that can have vey different volume levels. Even during the same section of the track we could have a drum hit so intense to be at much higher volume than the section’s average. The difference in volume between the lowest and the highest volume peaks is collade dynamics and it is measured in decibels (dB). A live recording may result in vert high dynamics, that is the volume differences between the moments played low and high are very large. When listening in your car or with mobile players and headphones, the high noise background may hide the low volume sections. The music industry’s solution has been to compress the musci signal in order to decrease those volume differences (the so called “loudness effect”). It as become such a mania that some recordings have just 2 or 3 dB dynamic range, compared to the 90 dB a CD would be capable of! Today a recording with 15 dB dynamic range is to be considered a good one! In the 80s we could easily find double that. Therefore, the quality of the recordings is very important, being it digital or analogue. It is also obvious that the most important thing of all is the artistic content. Old masterpieces from the history of music are certainly to be listened to regardless of the sound quality, since they are part of. For the abovereasons, we should pay much attention to remastered recordings, often worse than the originals. Unfortunately, many modern recordings, due exceptions made, are affected by high dynamic compression.
The audiophile’s life is not easy…
Article about dithering on tnt-audio.com to better understand digital issues
Pleasurize Music Foundation spreads the knowledge of dynamic compression in modern recordings.
Loudness war on tnt-audio.com
Apple iPod music player measurements on stereophile.com