NEC CD-803 Compact Disc Digital Audio Player
The CD-803 is no ordinary CD player, or it is based on NEC's many years of experience in all major areas of electronics and communications engineering - digital, optical, semiconductor laser, electronics, communications and precision machinery. No other CD player manufacturer has the technological background of NEC, the reason why the CD-803 provides unusually good sound quality and reproduction accuracy. Serious audiophiles and audio critics are now discovering what we already know; the CD-803 is the best executed CD player on the market.
What is a Compact Disc Digital Audio System.
Compact Disc Digital Audio is a system whereby an original analog signal is converted into a digital signal - a series of 0's and 1's in the binary code. This information, stored in the form of microscopic pits on a flat disc, is retrived by an optical (laser) beam, and finally converted back into analog form by a digital-to-analog (D/A) converter. The piece of audio equipment that retrives digital information from a CD and converts it into an analog audio signal is a CD player. The CD system offers tremendous advantages over the conventional analog system. For instance, dynamic range and s/n ratio both exceed 90 dB, and channel separation is better than 70 dB across an audio band extending from 5 Hz to 20 kHz. No wonder audiophiles and serious music lovers throughout the world have been awestruck by this new source of ultimate fidelity music.
Ease of operation
The CD-803 enhances ease of operation every bit as much as it improves sound quality. Advanced computer control means that it takes only minutes to learn every operating feature. Simply insert a disc into the front-panel door and touch the Open/Close button. As the door quietly closes, the disc rotates for a few seconds to enter encoded program data into the memory, and then stops. Now, by just touching the feather-touch operating buttons, you are ready to enter the realm of digital sound.
Memory play of up to 99 selections.
Up to 99 selections (tracks) on a disc can be programmed for play in any order. Moreover, by pushing the Repeat button, you can replay programmed selections as many times as you want. The average time it takes to locate a selection, or access track time, is only three seconds. For your convenience, when you've completed initial programming, you can confirm each programmed selection (its track number and order) on the display by just touching the Memo List button.
Digital-domain technology
A Compact Disc contains a sophisticated error correction signal. By extrapolation, it is possible to reconstruct the original digital pulses accurately in instances where some are unreadable. However, severe dropouts, caused by external noise or damage to the disc, may prove too much for the error correction system. This led NEC to develop a three-stage servo for the disc motor which accurately detects and corrects for dropouts. Faithful reproduction is assured.
Digital-analog interface technology
Digital signals are composites of both left and right channel information in alternating sequence. A switching circuit divides the composite signal into its left channel and right channel components. For this purpose, NEC developed an electronic switch which allows high-speed switching at a rate 10 times faster than commonly used C-MOS devices or analog switches. This significantly lowers high-frequency distortion. With the NEC electronic switching system, the signal runs in parallel with the Circuit rather than in series (as is the case with other switches(, so signal integrity is maintained.
Analog-domain technology
Once digital signals are converted into analog by the D/A converter, the sampling frequency (44,1 kHz) and its harmonic components must be eliminated completely by a low-pass filter. Commonly used active and passive filters suffer phase-related distortion called group delay, which led NEC to develop the ND (Non-Delay) filter. It reduces group delay at 20 kHz to 1/25 the value of other filter designs and significantly reduces unwanted spurious-frequency response.
Specifications
Player Section
System: Compact Disc digital audio Player
Pickup: GaAlSi Semiconductor laser
Sampling Frequency: 44,1 kHz
Quantization 16-bits linear/channel
Channels: 2
Frequency Response: 5 Hz - 20,000 Hz (±0,5 dB)
Dynamic Range: 90 dB or more
Signal-to-Noise-Ratio: 90 dB or more
Total Harmonic Distortion: 0,01% or less (5 - 20,000 Hz)
Channel Separation: 70 dB or more (5 - 20,000 Hz)
Wow and Flutter: Equal to crystal oscillator accuracy
Output Level
Fixed : 1,5 V, 470 Ω
Variable : 0 - 1,5 V, 2,5 k Ω
Program Search Function: program number or sub-number
Memory Functions: Random memory access to up to 99 programs
Access Time: 3 sec. average
Power Requirements: 100 /120 /220 /240 V AC, 50/60 Hz
Power Consumption: 58 watts
Dimensions (W x H x D): 430 x 150 x 360 mm
Weight: 12 kg
Disc Section
Playing Time (single-sided, 2-channel): 74 minutes 45 seconds maximum
Scanning Velocity (2-channel): 1,2 - 1,4 m/s
Rotation: Counterclockwise
Track Pitch: 1,6 µm
Diameter of Disc: 120 mm (4,8 inches)
Thickness of disc: 1,2 mm (0,0048 inch)
Diameter of Center Hole: 15 mm (0,6 inch)
Starting Diameter of program Area: 50 mm (2 inches)
No comments:
Post a Comment