NEC A-10 amplifier

NEC A10

The revolutionary Compact Disc places severe demands ion all equipment in the audio chain, particularly the amplifier. In order to reproduce ultra wide dynamic range music from digital sources with maximum accuracy, an amplifier must be able to reproduce high-energy transients at low distortion levels. The NEC A-10 is just such an amplifier, because it was specifically designed for the digital age.

The deficiencies of conventional power supplies.

A conventional amplifier power supply uses a capacitor-input filter" in its rectifier circuit in order to smooth out the current going to each of the amplifier circuits. However, in a common rectifier, the current at the filter output is not as smooth and steady as it should be. Instead, it fluctuates. This occurs because as one filter charges, the other discharges in a seesaw fashion. Extra loud musical passages place a massive current drain on the power supply. If this occurs when the current at the output of the filter is on the decline, the power-supply impedance will increase, which, in turn, causes a clipped waveform at the amplifier's output. the result is distortion.

The NEC Reserve Power Supply - more power for more solid bass.

The NEC Reserve Power Supply utilizes a switching circuit which instantly charges one filter the moment the other filter stops charging and starts discharging. Composite filtered current is much smoother and steadler. This keeps power-supply impedance constantly low, so that clipped waveforms do not occur even under heavily loads. The sound you hear is essentially devoid of distortion at all power levels, with bass sounding rich and powerful even during the loudest passages.

Sophisticated power supply design.

The NEC A-10 has a sophisticated power supply design that uses independent supplies for the phono amps (used with moving coil and moving magnet cartridges), buffer, voltage amp, and current amp. Moreover, to supply the power output stages, the Reserve Power Supply provides a big power reservoir for solid performance. NEC's sophisticated power-supply design assures consistently low distortion and solid, powerful bass reproduction at all output levels - the reason why the A-10 sounds far more powerful than its power rating suggests.

High-gain head amp for moving-coil cartridges.

The NEC A-10 features a separate, high-quality head amp for moving-coil cartridges to extract all the delicacy and subtlety MC cardridges are renowned for. Its high equivalent input noise of -154 dBV (at 90 µV /10 Ω ) is a good indication of the high caliber of this pre-preamp.

Simple Design

To ensure that the signal path is as simple and straight as possible, no tone control system is included in the A-10. In instances where tone control is needed or desired, NEC recommends that the A-10 be matched with a separate, high-performance graphic equalizer.

Specifications

Power Amplifier Section

Rated Output (both channels driven at 20 Hz - 20 KHz)

120 W + 120 W into 4 Ω 

60 W + 60 W into 8 Ω 

Total Harmonic Distortion:  0,003% or less (at rated output)

Intermodulation Distortion:  0,003% or less (at rated output)

Power bandwidth:  5 - 300 kHz 

Input Sensitivity:  1,23 V

Preamplifier Section

Input Sensitivity/Impedance

Phono MM :  2,5 mV/47 k Ω 

Phono MC-1 :  80 µV /10 Ω 

Phono MC-2 :  250 µV /100 Ω 

Tuner :  150 mV/30 k Ω 

Tape 1, 2 : 150 mV/30 k Ω 

CD :  150 mV/30 k Ω 

Aux :  150 mV/30 k Ω 

Output Level/Impedance 

Rec Out :  150 mV/100 Ω 

Preamp Out :  1,23 V/600 Ω 

Phono Overload Capability:  300 mV (MM)

Signal-to-Noise-Ratio: 

Phono MM :  90 dB (-142 dBV)

Phono MC-1 :  72 dB/90 µV  (-154 dBV)

Phono MC-2 :  83 dB/250 µV  (-154 dBV)

Tuner :  110 dB (-126 dBV)

Tape 1, 2 :  110 dB (-126 dBV)

CD :  110 dB (-126 dBV)

Aux :  110 dB (-126 dBV)

Subsonic Filter:  15 Hz (-3 dB, 6 dB/oct.)

Power Requirements :  100/ 120/ 220/ 240 V AC, 50/60 Hz

Power Consupmtion:  335 W

Dimensions (W x H x D):  430 x 150 x 430 mm

Weight:  20 kg

 

NEC CD-803 cd player

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)