Audio Database

The

NEC A-10TypeIV
125,000yen(October 21, 1987 release)

Description
 
The Integrated Amplifier which developed and improved A-10TypeIII further.

Simple&Straight thought is put into practice and, in addition to compact-disk direct input and Phono Direct Position which were carried by TypeIII, the main-amplifier part is made direct in TypeIV.
In order to avoid the influence of relay contact of the protection network which exists just before a speaker termination as much as possible, the speaker direct termination is adopted and the quality is improved much more by direct-drive achievement of a speaker.
Furthermore, the OCC shielded cable of the NEC original is adopted as the wiring in amplifier, and a tone and a feeling of energy with a bright transparent atmosphere and gloss are reproduced to it.
Moreover, the constant current drive scheme with little influence of a contact is adopted at the same time it adopts a more nearly high-definition thing also about a volume.

Reserve power-source dBASE III which improved the original reserve power source of NEC is carried.
Compared with A-10TypeIII, the capacity of a smoothing capacitor is reinforced 16% or more,Conventional power-source 20,000micro-Fx4, reserve power-source 3,300micro-Fx4, and the huge capacity of a total of 93,200 micro F are carried,The supply capacity of the charging current of conventional へ improved from the reserve, and the very smooth power-source wave has been obtained according to the recovery capacity after the Oide power to have excelled.
Moreover, the propagation by the side of [ the load variation generated in the sub- side of a transformer ] primary and noise mixing from the primary transformer side to the sub- side are improved.
Besides it, the very-thick OFC (oxygen free high conductivity copper) code is used for a power cord,Furthermore, the thorough refinement to the pureness of a power-source part, such as adopting the fuse with a lead which loses two contacts which intervene as a fuse holder, and supplies a power source to the primary transformer side direct, is carried out.

The mechanical grand construction is adopted as a rigid structure design.
About the component partses of each, the material and the structure of suppressing an oscillation thoroughly were selected carefully, a construction where the natural oscillation of each part article cancels mutually and which suits by a computer simulation on it was given, and the simple oscillation finally controlled is dropped into the huge foot.
In TypeIV, the tuning which makes a sintered alloy foot high-density is performed with a quality up of a signal system, and strengthening of a power supply system.
Furthermore, the power transformer was enclosed with the copper plating case, and while an oscillation peculiar to a power transformer is held down, the ill effect by leakage magnetic flux is also prevented by considering it as non-magnetic material.
Moreover, rectifier diode is also enclosed in a transformer case and holds down the rectification noise.
A selection of the 4/3-piece shorted to ground for choosing the setting environment and the delicate tone-quality difference of amplifier and point shorted-to-ground / interview place can be performed like TypeIII etc.

The push pull type amplifying circuit is adopted as circuitry in all the amplification stages.
Moreover, by considering the last amplification stage as a parallel push pull stream composition, the emitter resistor which goes into an output current circuitry in series is reduced by half, without spoiling the degree of safe, and the protection by an ASO limiter also makes a 2-ohm load intensity the unnecessary output circuit.

In order to perform a polar mandatory in system total including reversed-polarity software or a reverse motion speaker, the polarity-reversal Pre Out termination is carried.
By connecting the reversed polarity Pre Out and Main In by U character pin, a polarity is reversed by the separate position of an operation switchpoint, and total polar doubling is possible.

Operation of recording an FM broadcast is possible, carrying the REC selector scheme and hearing compact disk.

In order to prevent the influence of the tone quality by leakage magnetic flux etc. as much as possible, the front chassis is attaining non-magnetic-material-ization by copper plating. Furthermore, the non-magnetic-material material was adopted also as the rear panel, and various electric disturbance is eliminated by banishing the magnetic substance from the loop of the speaker output current.
Moreover, the large-sized vice type also corresponding to a very-thick speaker cable is adopted as a speaker terminal.

Rear
Internal

Rating of a mode
Form High-quality integrated amplifier
<Power amplifier part>
Circuit system Whole page direct DC servo circuitry
Effective output (both channel drive)
A sinusoidal input, 20Hz - 20kHz
120W+120W (4ohm)
60W+60W (8ohm)
THD (at the time of an effective output) 0.004% or less
Cross modulation distortion
(at the time of an effective output)
0.004% or less
Frequency characteristic 5Hz - 300kHz
Input sensitivity/impedance 1.23V/20kohm
<Preamplifier part>
Circuit system High Gm FET direct input DC servo EQ amplifier circuitry
Input sensitivity/impedance Phono man month: 2.5mV / 47kohm
compact disk, Tuner, AUX, Tape1, 2:150mV / 20kohm
An Output voltage/impedance Rec output: 150mV
Preamplifier output: 1.23V/600 ohm
SN ratio Phono:90dB(-142dBV)
compact disk, Tuner, AUX, Tape1, 2:110dB (-126dBV)
RIAA deflection Less than ±0.2dB
Phono maximum permissible input 150mV
Subsonic Filter 15Hz: -3dB, 6dB / oct
It is a partitioned to a phone equalizer.
(It is a non filter at the time of Phono Direct)
Input/output phase Inphase
However, only pre outs are those of straight polarity and reversed polarity with both the output.
<Synthesis>
Circuit system Shunt-regulator scheme + reserve power source
Power consumption 230W
Dimensions The width 430x height 165x depth of 485mm
Weight 27kg