SONY CDP-991
¥ 39,800 (released in 1990)
Commentary
A CD player equipped with a newly developed pulse 4D/A converter as well as custom edit and file functions.
The D/A converter consists of a high-density linear converter system, a 45-bit noise-shaping digital filter and a pulse D/A converter.
The Pulse D/A converter consists of a current source and an electronic switch. It expresses music waveform by switching two values of 0 and 1 at high speed. By this, the amplitude level is always constant and changes only in the time axis direction. The PLM (Pulse Length Modulation) wave is output. By passing it through a low-pass filter, unwanted high-frequency noise outside the audio band is removed and music waveform is obtained.
To reduce quantization noise in the audible band up to 20 kHz, the pulse D/A converter is equipped with a multi-stage noise shaping operation that employs 64 times oversampling and the Sony Extended Noise Shaping method. Oversampling reduces quantization noise in the audible band by increasing the sampling frequency. Noise shaping reduces quantization noise in the audible band by feeding back the requantization error to the input side when the number of bits is reduced. These technologies ensure a high dynamic range.
The pulse D/A converter operates at 45 mega pulses per second, and it completely eliminates differential non-linear distortion, glitch, and 0 cross distortion, which were difficult with conventional methods.
The CDP-991 uses a single-mode pulse D/A converter. A single pulse D/A converter provides a 4D/A output that outputs positive-phase and negative-phase LR signals.
To take advantage of the pulse D/A converter, the high-density linear converter system is equipped with a 45-bit noise-shaping digital filter in the front stage.
This circuit achieves a high dynamic range by performing a highly accurate oversampling operation and a first order noise-shaping operation on the operation result.
A direct digital sink is included to eliminate jittering issues.
In this system, the master clock is formed on the same chip as the pulse D/A converter, and jitter is eliminated in principle by eliminating jitter immediately before the electronic switch, which is the final stage of the pulse D/A converter.
The servo circuit is equipped with S Servo III.
In the S Servo III, the high-frequency noise component of the servo current is removed with a low-pass filter to supply a smooth servo current, which stabilizes the power supply from the power supply and prevents adverse effects on sound quality.
A digital CLV servo is installed in the drive system servo circuit that controls disk rotation.
The digital CLV servo detects the rotation of the spindle motor and controls it with 10-bit resolution to maintain an accurate linear velocity regardless of the disk's inner or outer circumference. It also detects the difference in inertial mass between the 12 cm CD and 8 cm CD disks to drive more appropriately.
Low noise and high stability are achieved by incorporating an RF amplifier in the pickup section.
The digital signal processing LSI uses the fourth generation LSI for the Sony CD player. Previously external RAM has been upgraded to a capacity of 32 kbit and built into the digital signal processing LSI. The precision of the signal processing capability is further enhanced by adopting the strict 6-fold error correction method.
Aluminum panel is used for the front panel.
It has a custom edit function and nine functions : peak search, time edit, just edit, program edit, multidisk program, link edit, time fade, variable fade, and manual fader.
In peak search, all songs are searched at high speed, and they are repeatedly played for about 4 seconds before and after the point where the volume level is highest.
Time Edit enables efficient editing of the A-side and B-side when recording tapes.
If you want to edit to fit the length of your tape, use the TIME SET button or AMS button to set the length of the tape (you can also use the direct key to set the length in seconds). Press the Edit button. First, program from the first song for side A. When you encounter a time-over song, select the longest song that fits within the time. Then press the Edit button to edit side B.
Also, if you select and edit a half disk with the AMS button, tracks are distributed so that the A side and B side of the tape are about the same length without changing the order of the songs.
Just Edit is an evolution of Time Edit. It automatically finds and programs the combination of songs closest to the specified time.
You can set the A side and B side at the same time as in Time Edit.
Program Edit allows you to manually edit your favorite songs in any order.
With the AMS key or direct key, you can program your favorite songs in any order while checking the accumulated time. If you turn on Auto Space at this time, you can edit each song by adding a 3-second blank to the playing time. When you press the pause button, you can program the A side and then the B side together.
Multidisk programs allow you to edit across multiple disks.
When you program in program mode and open the tray, the display "MULTI PGM" appears and the program automatically moves to a multi-disc program. You can program up to 6 discs (24 songs). You can also program poses in the middle of the program.
Link Edit allows you to add music to the remaining tapes from Time Edit or Just Edit.
If you have programmed all songs and there is room for more songs within the editing time, the track number of the song to be entered and the LINK display will blink, and you can add a song by reselecting from the songs with the blinking track number.
Link-edit also allows you to swap disks and continue editing.
Time Fade allows you to fade out at a specified time, which can be set with the TIME SET button or the AMS button.
You can set the fade-in / fade-out time for the variable fade from 2 seconds to 10 seconds in units of 1 second.
The manual fader allows you to fade in and fade out at the desired location.
Equipped with the custom file function, you can take advantage of 6 functions such as disk memo, custom index, program / delete bank, level file, last mode memory and file recall.
Disk Memo can record up to 10 characters per disk, 78 characters including alphanumeric characters, special symbols and blanks.
With a custom index, you can index the disc in your own way wherever you want in the index. You can set up to 10 points per disc and fine-tune it in steps of approximately ± 0.15 seconds.
In the Program / Delete Bank, you can record the settings of a program performance or a 99-track delete play.
The Level File feature lets you set different playback levels for different disks.
You can set the lineout / headphone volume to your desired volume by simply pressing the Level File button. When you insert the same disc, it is automatically set to the stored level.
In the last mode memory, you can store the play mode and fade time set just before removing a disc with a custom file. When the same disc is inserted, that mode is automatically recalled.
With File Recall, you can check what kind of file was stored.
This function can be function even if you don't have a disc installed, and you can delete unnecessary files on the fly.
It is equipped with a delete play function so that you can play continuously with only the music you want to listen to. If you delete unnecessary music in shuffle mode and then switch to continue mode to play, you can skip that music and play the next one.
In addition, it is equipped with a 99 track delete shuffle function so that you can leave only your favorite music and play it randomly.
It is equipped with Music Scan, so you can play only the beginning part of a song one after another.
You can choose from 3 kinds of playing time, 10 seconds, 20 seconds and 30 seconds.
Equipped with Auto Q, you can search automatically to the point where the sound rises in the pause state.
It is equipped with functions such as program performance function of up to 24 songs, 8-mode repeat of 1 song / whole song / part / program / delete play / shuffle / delete shuffle / custom index, and index search.
The display section has a 20-track music calendar.
In addition, the dimmer control function is installed, and the brightness of the display can be adjusted in 3 stages.
Equipped with an optical digital output.
Equipped with two line-out terminals, fixed and variable.
In addition, it is equipped with a headphone terminal with a lineout linked volume that flashes when the remote control is operated.
Wireless remote control is included.
This remote control is equipped with an auto-space function that adjusts the space between songs to a silent space of approximately 3 seconds. In addition, the display mode function switches the display area between all / partial ON / OFF.
Model Rating
| Type | CD Player |
| Reading system | Non-contact optical reading (using semiconductor laser) |
| Laser | GaAlAs double hetero diode |
| Number of revolutions | 200 ~ 500 rpm (CLV) |
| Playing speed | 1.2m/s ~ 1.4m/s (constant) |
| Error correction method | Sony Super Strategy Cross Interleaved Read-Solomon Code |
| Number of channels | 2 Channel |
| Frequency characteristic | 2 Hz to 20 kHz ± 0.3 dB |
| Total harmonic distortion factor | 0.0025% or less (EIAJ) |
| Signal-to-noise ratio | 113 dB or more (EIAJ) |
| Dynamic range | 100 dB or more (EIAJ) |
| Wow and flutter | Below the measurement limit (± 0.001% W. peak) (EIAJ) |
| Output level | 2Vrms(Fixed) 0 V ~ 2 Vrms (Variable) |
| Digital output | Optical : -18dBm (emission wavelength 660 nm) |
| Headphone output level | 28 mw (32 Ω) |
| Power consumption | 14W |
| External dimensions | Width 430x Height 115x Depth 340 mm |
| Weight | 4.5kg |
| Attachment | Wireless Remote Control RM-D991 |