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hobbyists's
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25 Years CD: August 17, 1982 - August 17, 2007
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When
the engineers in the world famous Philips Physics Laboratory start working
on the laser video disc around 1967, they will combine images and sound.
That brings about the idea of making a laser disc just for music and speech
with no images added. The final outcome is a disc of 12 cm in diameter
which is read by a laser beam. The disc has a reflective layer, covered
by a non reflective layer with holes of various lengths which measure
mere micrometers. These holes represent the recorded music. Only when
the laser beam is reflected by the disc, the beam is read by a photo cell
and the data which it represents is converted to an analog signal. |
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Sound
Premonition Analog
Sophistication Digital
Fear |
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These
are the first lines of an advertisement introducing the CD to the music
loving public. The advertisement appears in Dutch newspapers on the
1st of March, 1983. The first CD was pressed on August 17 1982 in the
Philips factory in Hannover, Germany, and was introduced in Japan on
November 1, 1982.
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Successor
to the Stereo Lp The
Beginning |
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RCA In that same article in the April 1966 issue of High Fidelity Magazine, RCA's Dr. Harold Olson tells the readers that the record of the future will be completely different: ''There will be no music on it, only a binary code''. He adds that only a very small disc will be necessary. The way the code will be read is also completely different. No needle or other mechanical devise will be used. Olson: ''The record could be read by an electron beam.'' It will be possible to record half an hour of music on a disc as small as the size of a quarter dollar (according to Wikipedia the quarter dollar measures 0.955 inches = 24.26 mm in diameter). The carrier is not necessarily a disc. The encoded information can be printed on a metal bar, or a piece of paper, or whatever object. In 1966 this means an upcoming revolution. It is the dawning of the age of the computer. |
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Futuristic In the April 1966 issue of High Fidelity, pianist Glenn Gould writes an essay on ''The prospects of Recording''. He goes even further and predicts that the listener will have a console with a keyboard in his listening room. After typing the title of the work he wishes to hear, say Beethoven's Emperor Concerto, he can choose from a list of available recordings. After entering the selected performance, the music signal will be sent by cable to his hi-fi set and a small sum will be deducted from his bank account. The prediction is that it will also be possible to store the entire performance in a chip (today that would be a memory stick , or a memory card) which can be bought in the "record shop". |
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Ampex Bell
Laboratories |
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Telefunken:
'Vinyl' Video Disc Primitive |
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Philips Video Disc: LaserVision. |
Philips
Video Disc: LaserVision Around 1967 the engineers of the famous Philips Natuurkundig Laboratorium (Philips Physics Laboratory) start researching the development of a video disc. It is an optical system instead of a mechanical one. Around 1980 the system will be ready for introduction and is named LaserVision. In 1967 the engineers realize, that, when omitting the images, they may have the possible successor to the Lp, the long playing record. In 1970 Wireless World reports about such a digital sound system. There are other magazines that publish more than once articles about the numeric formats of the future. For example Jean Hiraga writes in La Nouvelle Revue du Son about the systems that are being developed by manufacturers in Japan and Europe. In the nineteen seventies manufacturers do agree on the basic features and solutions for storing sound and images in a digital format. For the digital audio disc these are the features that have to be agreed on: maximum bandwidth (frequency band), number of bits, the physical aspects of a disc, and the ways of storing and reading the information. But a player is not yet in sight. |
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Denon
(Nippon Columbia) By 1973 the world wide adopted digital format is the 44.1 kHz/14 bit PCM format. PCM stands for Pulse Code Modulation. The sound is measured at specific intervals by a pulse. A higher sampling frequency than 44.1 kHz. and a higher quantization than 14, are not yet feasible. From then on Nippon Columbia (Japan) produces digital recordings and releases these on the Denon record label. The low quantization and bandwidth and the ringing of filters to prevent the mirrored audio band (aliasing) from interfering with the musical signal, prompt many audiophiles to say: "You can hear the switching." As if the variations of the samples and bits is the same as the shifting of gears in a race car. What they actually mean is that they are aware of the fact that the sound shifted from one dynamic level to another, from one bit to another. The later recordings done with 16 bit quantization are of course of a much higher quality and some are quite stunning in sound if compared to the later CD releases. Why? That will be explained later in this article. |
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Large
Catalog The specificatisons
of Denon's PCM recording system: |
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Miller
& Kreisel and Sony In the beginning of digital recording Sony U-Matic recorders in conjunction with separate converter modules are used. Sony develops their PCM 1600 Digital Studio Recorder which becomes very popular. It is eventually replaced by their PCM 1610. As these become available, more labels start recording digitally. Miller & Kreisel is such a label. The recordings are made with a Sony PCM 1600 with a sampling rate of 44.1 kHz. and the dynamic gradation of 16 bits. Jonas Miller and Ken Kreisel design their own electronics and modify the microphones. Their objective is to achieve a recording with the least phase shift and name it M&K RealTime Recording Process. |
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Soundstream,
Telarc, Digitech, a.o. Specifications
for the Soundstream Digital Recording System: |
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Sharp's prototype of a digital audio disc with 16 bit quantization and 44.1 kHz. sampling rate, stored on a 13.5 cm disc. |
Pioneer
and Sharp |
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The
development of the Philips Laser Video Disc (LaserVision) and its player
led to the creation of the CD-Video Disc and Player (introduced in 1987)
thus paving the way for the DVD. |
Sampling
Frequency Also the format Philips is working on is a linear system. This means that the number of samples vary with the frequency. The higher the frequency the fewer the samples. It also means that the width of the frequency band for audio depends on the chosen sampling frequency. In order to measure sound one sample is not enough. It is necessary to have at least two references, or samples, as I.S. Reed and G. Solomon had made clear. If we want to use the audio band of 10 to 20.000 Hz. we need at least two samples of the top frequencies. The result is that a sampling frequency of 44.1 kHz. gives a frequency band extending to half of that frequency, 20.500 Hz. A higher sampling frequency will result in a wider audio band. The later adopted 48 kHz. for the Digital Audio Tape Recorder (DAT) means an audio band extending to 24.000 Hz. A sampling frequency of 400.000 Hz. would mean an audio bandwidth from DC to 200.000 Hz. and practically no phase shift. The maximum resolution of a system is dependant on the clock frequency which in 1980 is rather low. A higher clock frequency gives a higher bit rate. |
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That is the time when
computer freaks are working with a Sinclair, a Commodore, an Atari, with
8 bit and a CPU with 4.43 MHz., storing data on a casette tape with time
consuming writing and reading.
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Petition When word gets around that Philips will propose a digital disc with the 14 bit/44.1 kHz format, editor/publisher Peter Aczel inspires the readers of The Audio Critic to send postcards to Philips in Eindhoven, the Netherlands, to urge the engineers to choose a sampling frequency of at least 50 kHz. But in fact even a sampling frequency of 50 kHz. would not be high enough to satisfy the discriminating listener, as only a much higher sampling frequency can produce upper harmonics and a true transient response. |
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Further
Development together with Sony
After consultations with Matsushita (Technics) and Sony, it is Sony who joins Philips to finalize the development of the Compact Disc. Philips has a 60% interest and Sony 40% in the joined venture. Apparently Philips is mainly responsible for the laser technology and Sony for the correcting codes. You all know the story that the capacity of the CD should enable the complete recording of Beethoven's Ninth Symphony, as Herbert von Karajan suggests. All physical and digital data are contained in The Red Book. But you only need ears to be able to judge the benefits of the medium. |
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Prototype of the CD. Like the Lp it has a paper label and the cover is a sleeve of thin card board. The jewel case has yet to be designed. |
1981:
Festival du Son in Paris In the Spring of 1981, well before the official introduction of the CD, Philips demonstrates their newly developed Digital Compact Disc at 'Le Festival du Son' in Paris. People are elbowing their way into the small auditorium to witness this historic event. When a Philips engineer needs to check the equipment and lifts part of a long and wide, gray curtain, it is immediately clear that Philips uses stacks of electronics: amplifiers and cabinets filled with digital circuitry for converting and correcting the signal. The interconnecting cables are thick and heavy. It shows all too well that at that time the elaborate circuits and complicated modules for conversion and correcting any mistake made while reading the disc, has not yet been reduced to a few ICs, chips and a couple of operational amplifiers. The cabinets filled with components recall pictures of a demonstration at a World Fair in the early years of the past century. There is something primitive about it. But there is also the thrill of witnessing the beginning of a new era: sound recording and reproduction by means of a computer. The development of tiny converters and operational amplifiers is certainly on its way. But no risk shall be taken during such an important demonstration. Yet it will not take long before electronic circuits and converters are reduced to the size of a mere IC. |
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Louis
Armstrong and Mussorgski Many do remember the demonstration of Louis Armstrong's digitally remastered trumpet, sounding round without a chiseled top. Also an original digital Philips recording of Mussorgski's "Pictures at an Exhibition" performed by the Concertgebouw Orchestra, conducted by Sir Colin Davis, can be heard. The introductory trumpet sounds indeed unstable, is shifting in intensity from bit to bit, as it is recorded at a low level. Apparently no dither is added as it is not yet en vogue. The recording is also issued as Lp with reference number 9500 744 and a few years later as CD 411-473-2. Listening to this recording in whatever format, it is clear that the recording technician is still "thinking analog". The reason for the less than precise reproduction during the demonstration is not because the new constructed format does not work properly. It certainly works as correctly as the format dictates with the components of that moment. The actual reason is that the format is too restricted to really render the nature of the trumpet. Philips demonstrates with 14 bits converters, eventually enhanced with the technique of noise shaping. Only much later pure 16 bit conversion in combination with oversampling is applied in the Philips CD players. Yes, the demonstration shows that the sound is as clear as light. That is true. But the demonstration makes clear that the sound is also incomplete. And when two years later the first Philips player, the CD-100, is introduced, many a music lover can hear the "clear'' sound in their own listening room. |
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Remarkable
Feat
No doubt, the creation of the Compact Disc is a technical feat of the highest order. Taking the given format of 44.1 kHz. and 16 bit, designing a method for storage, incorporating algorithms with the codes for the signal, the correction of the signal, for the steering of the disc's speed in order to ensure the same density of information at every diameter, adding calculators for restoring the signal if a reading would be incorrect, and finally putting the audio signal plus this extra information, including the filtering, in a series of pits on a very small disc instead of a heavy, 12 inch silver disc as other manufacturers propose... that surely is a technical miracle. And do not forget about designing and building a pressing plant where all vital aspects of the production in a dust free surrounding are attended to (though in the first years many discs show imperfections and cannot be played entirely). And finally the development of the design of a container (jewel case) which protects the CD makes the product complete. If you want to know more about the details of the technique, you can consult Giesbert Nijhuis page. At right: Philips Lp 9500 744 and CD 411-473-2 respectively. |
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Point
of View That is looking at the medium from a technical point of view, that is looking from the point of view of the proud engineers of the Philips laboratory, the point of view of the Sony engineers, the point of view of the marketing people and the record companies who - first reluctant - finally will accept the new world standard, a format with a channel bit rate of 4.3218 Mb/sec and a data bit rate: 2.0338 Mb/sec. Yes, there is no dust in the groove, there is the absence of the sound of the stylus in the groove, there are no scratches, there are no dents, no pressing bubbles. But the serious music lover who knows how acoustic instruments do sound, is judging the new medium with cautious ears. It is said that the late Jaap van Ginneken (producer, Polygram Records) has his doubts. |
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16 bit and 44.1 kHz.

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Bandwidth 700.000
Hz. Sampling Frequency |
| Aliasing In the linear CD the audio band up to 22.05 kHz. is mirrored, has an alias. Not a bit of the 22.05 to 44.1 kHz. band shall interfere with the music. In order to prevent a mix up, the insertion of a steep filtering by means of a so called brick wall filter, is applied. In theory the slope of that filter should be 96 dB. That is a very difficult value to implement with an analog filter. That is why sometime later the filtering will take place in the digital domain. This makes it possible to insert a less steep filter in the analog domain. |
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Samples The number of samples in the audio band is frequency dependent. The lowest frequencies are being measured many times more than the top frequencies. The frequencies from about 11.000 Hz. to 20.000 Hz. are sampled only 2 times. There is another important trait of the CD format. The highest resolution of the sound is attained at the loudest level, that is at 0 dB recording level. 0 dB gives also the least distortion. At lower levels, the resolution is less and is not in line with that of the 0 dB level. The lower the level, the less the resolution. Every bit measures 6 dB. 16 bit means a dynamic range of 96 dB, no matter if the original recording was made at 20, 24, 32 or even 64 bit. |
Oversampling

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Refining The computer of the PCM recorder has a steep filter otherwise recording was not possible. The same goes for the CD Player. There is however a way to avoid such a filter with a very steep slope. The Philips engineers introduce the so called oversampling. This is a very clever technique. By multiplying the sampling frequency by 4, the sampling frequency will be seen as 176.4 kHz. instead of 44.1 kHz. and an audio bandwidth of 88.2 kHz. is suggested. This also means that the aliasing is far away from the music signal, the actual audio band of 10-20.000 Hz. Yes, 176.4 kHz. would be quite an ideal sampling frequency. Such a high frequency does not need a steep filter. This multiplication has the benefit of "interpolation". Steps between one level (bit) and the next level (bit) are being generated. This results in a more analog like sound wave. |

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16
Bits Reverberation
and Depth 96
dB Restriction |
Sigma Delta

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All
drawings Copyright by Rudolf A. Bruil
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High
Resolution Digital Natural
Harmonics |
Sophistication
The Versatile Lp
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Expensive Limited
Frequency Band |
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Analog
Lp Record and UDF At left the covers of The Last Sony-CBS Lp pressed in the Netherlands in March of 1998. The factory was sold and is still pressing some 6 million records a year. The other cover is of digital Philips Lp 6570 994 from 1981 including a catalog of the first Philips digital recordings of classical music. |
©
Rudolf A. Bruil. Page first published on August 17, 2007 and expanded since.
This is the translation and adaptation of an original article,
written in Dutch and published in the Spring of 1993.
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