NEC CD-830DS

Commentary

A CD player equipped with new technologies such as newly developed digital servo and optical pickup with built-in I/V amplifier.

A newly developed 16 fs Transversal Filtering Circuit is mounted.
In this circuit, an average interpolation system is constructed by adding a signal with 1/2 times delayed period to the signal with 8 times over-sampling. Since the sampling frequency is pseudo-doubled, the hold aperture time becomes 1.4 μ sec, which is 1/2 of the 8 times over-sampling time, and a smoother waveform is obtained. In addition, random noise becomes 1 / √ 2 by adding data, and S/N ratio improvement of about 3 dB is achieved. Furthermore, the energy to be interpolated by the low-pass filter becomes half (-6dB), which reduces the load on the low-pass filter, making it possible to expand the passband and improve the phase distortion.

The 4 dac Balanced Summing System is used for the D/A conversion part.
This system uses two D/A converters each for Lch and Rch. The in-phase noise of the + and - D/A converters can be canceled each other, and at the same time, the random noise can be reduced to 1 / √ 2. The S/N ratio is improved by more than 3 dB compared to the conventional system.
In addition, a Glitchless D/A converter has been adopted to simplify the circuit configuration by cutting off the sample-and-hold circuit that generates spike noise and adversely affects sound quality.

An optical pickup with a built-in I/V amplifier is used for the pickup section, which integrates a PIN photodiode with a 6-division pattern and six I/V conversion amplifiers with a single power supply operation on the same chip by making full use of a bipolar process with two layer wiring and reducing the chip size and shielding the IC section.
As a result, the output of the optical pickup becomes a voltage-variable type and the output impedance can be lowered, reducing the influence of external noise, reducing the error rate and improving the sound quality.

We have developed and installed the world's first digital servo circuit in order to realize faithful and optimum servo.
This servo circuit consists of a newly developed dedicated LSI μ PD6353G, which integrates a digital loop filter for focus servo and tracking servo, a PWM (pulse width modulation) output circuit, a one track jump control circuit, a track jump counter, a brake circuit, an RF signal detection circuit, and an RF comparator on one chip.
By integrating the focus servo and tracking servo independently, an arbitrary filter coefficient (gain, time constant, etc.) can be set by the system control microcomputer according to the change of the pickup condition. Unlike conventional analog servo circuits with fixed filter coefficient, the servo is flexible and faithful to the change of the signal from the disk.
In addition, the integration of IC functions improves reliability, and the PWM (Pulse Width Modulation) drive of the pickup servo reduces energy loss at the servo driver stage.

A 2.0 mm thick steel plate is used for the bottom plate, and the center chassis is used to absorb microvibration from the internal rotation system. In addition, the structure is resistant to external vibration by making the sintered alloy legs (φ 66 / 18 mm) with high rigidity and excellent vibration resistance adhere to the floor surface. (Point contact and interview site can be selected)

The digital stage and analog stage are completely separated from the power transformer to prevent noise from entering the analog stage.

Equipped with an absolute phase (signal polarity) change-over switch, it is possible to match the polarity of the whole system with that of the source.

Equipped with digital (optical / coaxial) output.

An optical transmission method is used to prevent adverse effects caused by digital signals.

Very thick OFC cord is used for the power cord.

Equipped with performance time editing functions such as digital fade-out function, auto-edit function, manual edit function, disc change edit function, auto-space function, and display of music within remaining time.
In addition, the following functions are available : delete program playback, random play, introscan, 24-track random program memory, 3-mode repeat function between all songs / programs / A and B, time search, track search, index search, 2-speed music search, power ON start function, and 6 types of time display.

It uses a large display with a music calendar with 3 levels of brightness switching.

Equipped with a headphone port with volume.

Wireless remote control is included.

Model Rating

Type	CD Player
Frequency characteristic	5 Hz to 20 kHz ± 0.5 dB
Total harmonic distortion factor	Not more than 0.0025%
Dynamic range	98 dB or more
Signal-to-noise ratio	105 dB or more
Channel separation	103 dB or more
Wow and flutter	Measurement limit value or less (crystal oscillation accuracy)
Output level	2.5Vrms
Pwer	100 VAC, 50Hz/60Hz
Power consumption	25W
External dimensions	Width 430x Height 90x Depth 320 mm Width 430x Height 112x Depth 328 mm (max)
Weight	11.5kg
Attachment	Wireless Remote Control AR-830DS