SONY dadc_minidisc_handbook 维修电路图.pdf

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1、MINIDISC MANUAL V3.0E 收音机爱好者资料库 Ra d i o Fa n s .CN Table of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. The MiniDisc System 1.1. The Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2、. 2 1.2. What it is and How it Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Serial Copy Management System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4. Additional Features of the Premastered MD . . . . . . . . . . . . . . . . . . . . . 8 2. The producti

3、on process of the premastered MD 2.1. MD Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2. MD Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3. Input components specification 3.1. Sound Carrier Specification

4、s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2. Additional TOC Data / Character Information . . . . . . . . . . . . . . . . . . 17 3.3. Label-, Artwork- and Print Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.4. MiniDisc Logo . . . . . . . . . . . . . . . .

5、 . . . . . . . . . . . . . . . . . . . . . . . . . 23 4. Sony DADC Austria AG 4.1. The Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5. Appendix Form Sheets 收音机爱好者资料库 Ra d i o Fa n s .CN Introduction The quick random access of Compact Disc players has b

6、ecome a necessity for music lovers. The high quality of digital sound is now the norm. The future of personal audio must meet the above criteria and more. Thats why Sony has created the MiniDisc, a revolutionary evolution in the field of digital audio based on an advanced miniature optical disc. The

7、 MD offers consumers the quick random access, durability and high sound quality of optical media, as well as superb compactness, shock- resistant portability and recordability. In short, the MD format has been created to meet the needs of personal music entertainment in the future. Based on a dazzli

8、ng array of new technologies, the MiniDisc offers a new lifestyle in personal audio enjoyment. 收音机爱好者资料库 Ra d i o Fa n s .CN The Features A AD DC CD D A U S T R I A 2 1. The MiniDisc System 1.1. The Features With the MiniDisc, Sony has created a revolutionary optical disc. It offers all the features

9、 that music fans have been waiting for. Quick Random Access The MiniDisc offers quick random access to the music selection or phrase of your choice; something only a disc is capable of. Total Durability The MiniDisc can never stretch, break or tangle like cassette tapes. Since the free floating opti

10、cal pick-up never touches the surface, scratches are impossible. Superb Compactness The MiniDisc itself is only approximately 64 mm in diameter, and the cartridge is 72 x 68 x 5 mm.And because the MiniDisc is smaller, so is the MiniDisc player. Shock-Resistant Portability The MiniDisc is resistant a

11、gainst shocks and vibrations. New technology, using an advanced semiconductor memory, provides almost total shock resistance so there is no skipping and jitter even while jogging or driving. Easy to Handle The disc is protected in a cartridge. It is easy to handle and the ideal sound carrier for mob

12、ile use. Unsurpassed Digital Sound The MiniDisc is based on the same noiseless and distortion-free digital recording technology as the compact disc. So whether you are recording your own or listening to prerecorded music, you have the optimum in audio quality wherever you go. Recordable Disc 4 Track

13、 Recording: “A disc which records” is every music fans dream come true. The MiniDisc offers about 74 minutes digital recording on one tiny disc. What it is and How it works A AD DC CD D A U S T R I A 3 + - Cross sectional view of recording track LaserLaser High intensityLow intensity 01 Recordable d

14、iscPremastered disc 01 + + MD Objective Lens Polarized beam splitter Photo Detector A Photo Detector B Laser Beam MO signal Pit signal Re cor din g tra ck 1.2. What it is and How it Works Two Kinds of MiniDiscs are Available: Premastered MiniDiscs for Music Software Premastered MiniDiscs are used mo

15、st commonly for music and are sold in record stores just the same as compact cassettes and CDs are. MiniDiscs, just like CDs, are manufactured in large volumes by high-speed injection molders, and the music signals are recorded during repli- cation in the form of pits. Forget the times when you woul

16、d worry about cassette tapes becoming worn out or wrinkled. Moreover, the discs are encased in a cartridge, so there is no worry about their being scratched. The design of the premastered MiniDisc cartridges Optical Pick-up of MD Player: is special. Prerecorded music packages require a label, featur

17、ing the artists picture or other infor- mation for it is the artwork that most often captures the buyers eye. Therefore the top face of the cartridge is left completely free for the label. A window for the laser beam to read the disc is only necessary on the bottom face. Recordable MiniDiscs Magneto

18、-optical (MO) technology forms the heart of the recordable MiniDisc technology. Not only are MO discs durable enough to withstand being rerecorded about 1 million times, they also have a life expectancy approaching that of CDs. When recording the MO discs, a laser beam must be focused onto the magne

19、tic layer from behind while a magnetic field is applied to the front. For this reason, the cartridges for recordable MiniDiscs have a read/write window on both sides. The optical pick-up developed for the MD system has the remarkable ability to read both recorda- ble and premastered MiniDiscs. For r

20、ecordable discs, the pick-up detects the magnetic structure along the track. For premastered optical discs, it detects the geometric structure along the track. The MD system is based on the design of the standard CD pick-up with the addition of a MO signal readout analyzer and two photodiodes. Durin

21、g playback of recordable discs a 0.5mW laser is focused onto the magnetic layer. The magnetic signal on the disc affects the polarization of the reflected beam. The direction of polarization is converted into light intensity by the MO signal readout analyzer. Depending on the direction of polarizati

22、on one of the two photodiodes will detect more light. The electrical signals from the photodiodes are subtracted and depending on whether the difference is positive or negative, a “1” or “0” signal is read. MiniDisc Pick-up Technology Laser BeamMove direction of Disc NewOld Recording Head Head Drive

23、 signal 0 1 SSNNSSNN Heated area by Laser above Curie Point (erased magnetic pattern) Magnetic field of Recording Head Cross section of MO-Layer with magnetic pattern Top view of one Track Frozen magnetic pattern after cooling below Curie Point What it is and How it Works A AD DC CD D A U S T R I A

24、4 The same 0.5mW laser is used for the playback of premastered optical discs. The amount of light reflected depends on whether or not a pit exists on the surface of the disc. If there is no pit, a high proportion of the light is reflected back through the beam splitter and analyzer into the photodio

25、des. If a pit does exist, some of the light is diffracted and less light reaches the photodi- odes. The electrical signals from the photodiodes are added up in this case and depending on the sum, a “1” or “0” is read. Overwrite Technology In order to meet the requirements of a compact, lightweight,

26、recordable audio system for perso- nal use, the MD system employs a newly develo- ped Sony magneto-optical (MO) disc that utilizes magnetic field modulation with direct “overwri- te” capability. With MO disc technology, the recording of data requires the use of a laser and a polarizing magnetic fiel

27、d. When the magnetic layer in the disc is heated by the laser to a tem- perature above the Curie point (approximately 200 C), it temporarily looses its coercive force. As the disc rotates and the irradiated domain returns to normal temperature, its magnetic ori- entation is determined by an external

28、ly applied magnetic field. Polarities of “N” and “S” can thus be recorded, corresponding to digital data “1” and “0”. Unlike conventional MO rewrite mechanisms, the ”Sony MD overwrite system” positions a magne- tic head directly accross from the laser source on the opposite side of the disc. A magne

29、tic field corresponding to the input signal is generated over the laser spot. The rotation of the disc then displaces the area to be recorded, allowing the temperature at the spot to drop back below the Curie point. At that point, the domain takes on the polarity of the applied magnetic field regard

30、- less of the polarity that previously existed. Overwrite Mechanism What it is and How it Works A AD DC CD D A U S T R I A 5 The ease of quick random access was made possi- ble by the development of the Compact Disc (CD). The CD instantaneously provides random access to the beginning of any desired

31、music selection. After using a CD player, the time to reach the music sel- ection of your choice with cassette tape players seems extremely cumbersome. The MiniDisc provides the same high-speed random access for recordable discs as well as for premaste- red discs. In addition, the recordable MiniDis

32、c has a circumferential microgroove or ”pre-groove”, which is formed when the polycarbonate substrate is injec- tion molded. This pre-groove is the basis for the tracking servo and spindle servo operation during recording or playback. Address information is recorded at intervals of 13.3 milliseconds

33、 using a technology that places infinite- simal zigzags on this pre-groove. Therefore, the disc has all the addresses already notched along the groove even with no recording. The result is a stable and quick random access, as well as a variety of optional features, including programming of the playb

34、ack sequence e.g.: rearranging the sequence of the titles recorded on the MD without rerecording of the music information in a matter of seconds. This is possible because of the “User TOC Area”, located around the inner edge of the microgroove, which only contains the order of the music. This system

35、 is similar to the “directory management system” of floppy discs. In other words, starting and ending addresses for all music tracks recorded on the disc are stored in this area, enabling easy programming just by rewriting the addresses. This supports also other features: it is possible to erase a t

36、rack out of a sequence and during playback no gap in the remaining music will be heard. The era- sed segment is allocated to the free space it is possible to record a piece of music independent of the number of segments used. Quick Random Access Lead in1234Lead out AB CD EF GHInner EdgeOuter Edge Di

37、sc Signal Lead in123Lead out A: Before Rearranging B: After Rearranging Music Data and Order are Recorded Time-Wise 1. Ordinary Method: Rearranged Area Lead in UTOCOnly Music Data is Recorded Lead out 1 2 3 4 UTOC Data TNOSTARTSTOP A C E G B D F H Disc Signal 2. MiniDisc: Music Data and Order are Re

38、corded Area-Wise A: Before Rearranging Lead in UTOCOnly Music Data is Recorded Lead out 1 2 3 UTOC Data TNOSTARTSTOP A E G D F H Rearranged Area Connecting two Tracks: B: After Rearranging (No Change of Music Data) Additional Reprogramming the Order: 1 2 3 TNOSTARTSTOP A G E D H F Reprogramming the

39、Order of Music Threshold of Hearing: As sound level diminishes, there is a level below which the human ear cannot detect. This thres- hold varies with frequency. The threshold of audibility is lowest for sounds with a frequency of approximately 4kHz; that is, sounds close to this frequency are most

40、easily detected by the ear. By analyzing the frequency components of an audio signal, it is possible to identify those components that lie below the threshold of hea- ring. Such components can be removed from the original signal without affecting perceived sound quality. Masking Effect: If two sound

41、s, one loud and the other soft, are produced simultaneously and they are close to one another in frequency, the softer sound be- comes difficult or even impossible to hear. Therefore, when an audio signal has a high level component and a low level component at neigh- bouring frequencies, the latter

42、can be removed without affecting perceived sound quality. Moreover, with increasing overall signal amplitu- de, it becomes possible to remove a greater num- ber of components without audible effect. What it is and How it Works A AD DC CD D A U S T R I A 6 0.02 msec 11.6 msec Level analyze the wavefo

43、rm during approx 11.6 msec into frequency components Time Level Frequency F1 512 Samples Level Frequency F4 Level Frequency Fn Waveform analysis: ATRAC Digital Audio Compression Technology In order to provide approximately 74 minutes of music on the 2.5-inch MiniDisc, a digital audio compression tec

44、hnology called “ATRAC” (Adaptive Transform Acoustic Coding) has been newly deve- loped. This technology compresses information down to approximately one fifth of the amount of data usually required. In 16-bit linear encoding, currently used in the CD and DAT formats, with a sampling frequency of 44.

45、1 kHz, the analog signal is sampled approxim ately once every 0.02 milliseconds. Each sample is quantized at 16-bit resolution into one of 65536 possible values. Therefore, with CD and DAT, when the analog signal is converted to digital data in real time, 16 bits of data are used every 0.02 millise-

46、 conds, regardless of the amplitude of the signal and whether or not a signal is present at all. ATRAC starts with the same 16-bit digital data but analyzes segments of the data for waveform content every 11.6 msec. Based on this analysis, ATRAC extracts and encodes only those frequency compo- nents

47、 that are actually audible to the human ear. This method of encoding is far more efficient than the linear coding technique used for CD and DAT, yet sound quality remains comparable. The following underlying psychoacoustic principles are used during this conversion. Psychoacoustic principles: Maskin

48、g Effect F6FnF4F1 504004k20k Threshold of Hearing Level Sampling Distribution and Acoustic Effect Level F6FnF4F1 504004k20k Freq. (Hz) Sampling from ATRAC and its Level Shock-Resistant Memory Conventional optical pick-up systems can easily mistrack when subjected to shock or vibration. In digital au

49、dio CDs, this causes “skipping” or muting. Resistance to shock and vibration is a vir- tual prerequisite for true portable personal audio applications. In the MD system, Sony has solved this problem with a unique shock-resistant memory. While the MD pick-up can read information off the disc at a rate of 1.4Mbit per second, the ATRAC decoder requires a data rate of only 0.3Mbit per second for real time playback. This difference in processing speed enables the use of a readahead buffer, placed between the pick-up and the decoder. If a 4Mbit memory chip is