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| NEC A-700 |
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| 79,800yen(1985 release) |
The Integrated Amplifier which aimed at the
improvement in the operationality corresponding to audio-video age supplying the
original technology of NEC, such as a reserve IBM-PCN-II power source.
A
push pull type amplifying circuit is adopted as all the amplification stages, and the last amplification stage has become circuitry with the parallel push
pull stream composition. By carrying out the parallel using of the output
transistor for the substantial reduction by half by the emitter resistor which
goes into an output current circuitry in series, stability was not spoiled but
it has realized.
Furthermore, it is made the setups in which the limiter
which spoils the linearity of output power does not operate in a 2-ohm load
intensity by the output circuit development which does not need the protection
by an ASO limiter.
The original reserve IBM-PCN-II power source of NEC
is carried in the power-source part.
Another power source with which time
for the charging time of a capacitor input type rectifier circuit not to flow is
compensated was used for this, and it delayed the phase of the output 90
degrees, is a flume detour way scheme by which the valley of a ripple is filled, and, thereby, has strengthened the stability.
Even if it is going to acquire
the Oide power by this at the time of the capacitor electric discharge generated
with the conventional capacitor input type power source, the hangup that supply
voltage will fall is solved.
Moreover, the line filter which cuts a
power-source noise into an AC outlet is carried.
The mechanical ground
construction is adopted as a vibration-proof rigid structure design.
This is
stopping the ill effect which mechanical vibration has on an electrical circuit
by review of the chassis structure of clarifying the ground point of not only
the ground potential that is an electric reference point but mechanical
vibration.
In A-700, the opportunity reference point of the set itself is
made into the structure which responds to all the mechanical vibration on foot
as a foot of a main unit, and the product made from a sintered alloy 50mm in
diameter and 22mm in height is adopted as a sole plate.
Moreover, in order
to connect a structure division article and a power transformer to a foot
certainly, the 2.0mm griddle in thickness is adopted as a sole
plate,Furthermore, a cloth beam is connected with adoption of the cloth beam
which solid-construction-izes sub- metal fittings on either side, rear panel, and heat sink, and a sole plate with two beams, and the core of a power
transformer is certainly fixed to a beam.
This has gained the bass by
variation of the stray capacity on a signal line, and a floating inductance
which pressed down the failure of distortion, a crosstalk, and a phase response
etc. and sat on the waist, and sharp loud sound.
Although it1
circuitries, such as a tone defeat, were established in the tone circuitry and
it was coped with by switchpoint changeover in the former in it, in order that a
signal might pass a switchpoint contact even in this case, the tone-quality
failure was received.
In order to cope with this, excessive amplifier and a
switchpoint contact were not passed, and the main direct tone circuitry which
controls the property of direct sending and a main amplifier themselves for a
signal directly to a main amplifier is developed and adopted.
Moreover, its attention is paid to the delay characteristics at the time
of a music play, especially the variation of right-and-left both channels,The
group delay by a computer simulation, a phase, a setups of the optimum
value of each property of a swing,Adoption of the audio peculiar part selected
carefully for the impedance of a bus / treble both volumes and the mandatory
of a correction curve, and the mandatory of the allowable error of a circuit
constant etc. has realized the tone circuitry excellent in a feeling of
a lateralization.
In order to
correspond also to an analog play, the high gain equalizer amplifier is carried.
Low-noise Hi-GmFET which was excellent in the tone quality is used for the
differential amplifier, and also the shunt type power source for exclusive use
is carried.
Two input terminals and one output-terminal for visual
equipments are carried.
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| Form |
High-quality integrated amplifier
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| <Power amplifier part>
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| Circuit system |
Whole page direct DC servo circuitry
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Effective output (both channel drive)
They are 20Hz - 20kHz at the time of a sinusoidal consecutive output.
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100W+100W (4ohm)
50W+50W (8ohm) |
| THD |
0.006% or less (at the time of an effective
output) |
| Cross modulation distortion |
0.006% or less (at the time of an effective
output) |
| Frequency characteristic |
5Hz - 300kHz |
| Tone control |
High-Precision tone circuitry (±3dB)
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| <Preamplifier part>
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| Circuit system |
High-Gm FET direct input EQ circuitry
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| Input sensitivity/impedance |
Phono(man month/MC): 2.0mV / 20kohm
compact disk, Tuner, Tape1/2 (Video), Tape3/4 (Audio), AUX:150mV /, 20kohm
(Picture signal: 1 Vp-p/75ohms) |
| An Output voltage/impedance |
Tape1, 2 and 3, 4 Rec:140mV /, 2.2kohm
Monitor: 1.0 Vp-p/75ohms |
| SN ratio |
Phono(MM/MC):90dB(-142dBV)
compact disk,
Tuner, Tape1, 2, 3 and 4, AUX: 110dB (-126dBV) |
| RIAA deflection |
Less than (10Hz - 40kHz) ±0.2dB
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| Phono maximum permissible input |
MM:150mV |
| Subsonic Filter |
5Hz (-3dB, 6dB / oct, phone equalizer
inclusion) |
| Input/output phase |
Inphase |
| <A power-source part,
others> |
| Circuit system |
Shunt power-source scheme + reserve
IBM-PCN-II power source |
| Power consumption |
190W |
| Dimensions |
The width 430x height 120x depth of 380mm
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| Weight |
14.0kg |
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