NEC A-10TypeIV

Commentary

Pre-main amplifier further developed and improved from A-10TypeIII.

In addition to the CD Direct Input and Phono Direct Position installed in the TypeIII, the TypeIV uses a direct main amplifier.
In order to minimize the influence of the relay contact of the protection circuit which exists just before the speaker terminal, the speaker direct terminal is adopted. By achieving the direct drive of the speaker, the quality is further improved.
In addition, NEC original OCC shielded cable is used for the wiring inside the amplifier to reproduce bright and transparent atmosphere, glossy sound and energy feeling.
As for the volume, we have adopted a higher quality model and a constant current drive system that is less affected by contact points.

It is equipped with reserve power supply III which is an improvement of NEC original reserve power supply.
Compared with the A-10TypeIII, the capacity of the smoothing capacitor has been increased by more than 16%. It is equipped with a huge capacity of 93,200 μ F in total with a conventional power supply of 20,000 μ Fx4 and a reserve power supply of 3,300 μ Fx4. The capacity to supply the charging current from the reserve to the conventional is improved, and the excellent recovery capability after a large output provides an extremely smooth power waveform.
We have also improved the transmission of load fluctuations from the secondary side of the transformer to the primary side and noise contamination from the primary side to the secondary side of the transformer.
In addition, the power cord is a very thick OFC (oxygen-free copper) cord, and a fuse with a lead is used as a fuse holder to supply power directly to the primary side of the transformer without two intervening contacts. Thus, the purity of the power supply part is thoroughly refined.

Mechanical ground construction is used for rigid structural design.
Each part is made of carefully selected materials and structures that thoroughly suppress vibration. On top of that, the natural vibration of each part is made to cancel each other by computer simulation. Finally, the controlled simple vibration is incorporated into a huge leg.
TypeIV is further tuned to increase the density of the sintered alloy legs with improved signal quality and power supply system.
In addition, the power transformer is enclosed in a copper-plated case to suppress the vibration characteristic of the power transformer. At the same time, the transformer is made non-magnetic to prevent adverse effects caused by magnetic flux leakage.
A rectifier diode is also enclosed in the transformer case to suppress rectification noise.
As with TypeIII and other products, you can choose between 4/3 landing gear contact, point contact, and contact area in order to select the installation environment of the amplifier and subtle sound quality differences.

A push-pull amplifier circuit is used for all amplifier stages.
In addition, by adopting a parallel push-pull configuration for the final amplifier stage, the emitter resistance which goes in series with the output current circuit is reduced by half without loss of safety, and the output circuit does not require protection by an ASO limiter even with 2 Ω load.

In order to manage the polarity of the system as a whole, including reverse polarity software and reverse motion speakers, a polarity inversion Pre Out terminal is mounted.
Reverse polarity By connecting the Pre Out and Main In with a U-shaped pin, the polarity can be reversed with the operation switch in the separate position and total polarity adjustment is possible.

Equipped with a REC selector system, it is possible to record FM broadcasts while listening to CDs.

In order to minimize the effect of sound quality due to magnetic flux leakage, etc., the front chassis is made non-magnetic by copper plating. In addition, a non-magnetic material is used for the rear panel to remove magnetic material from the loop of the output current of the speaker, thereby eliminating various electrical disturbances.
The speaker terminal is a large vise type that can be used with very thick speaker cables.

Model Rating

Type	High-quality integrated amplifier
Power Amplifier Unit
Circuit system	All-stage direct DC servo circuit
Effective output (both channel drive Sine wave input, 20 Hz to 20 kHz)	120W + 120W (4 Ω) 60W + 60W (8 Ω)
Total harmonic distortion factor (at effective output)	Not more than 0.004%
Cross modulation distortion factor (at effective output)	Not more than 0.004%
Frequency characteristic	5 Hz to 300 kHz
Input Sensitivity / Impedance	1.23V/20k Ω
Preamplifier Section
Circuit system	High Gm FET Direct Input DC Servo EQ Amplifier Circuit
Input Sensitivity / Impedance	Phono MM : 2.5mV/47k Ω CD, Tuner, AUX, Tape1, 2 : 150mV/20k Ω
Output Level / Impedance	Rec output : 150 mV Preamplifier output : 1.23V/600 Ω
Signal-to-noise ratio	Phono:90dB(-142dBV) CD, Tuner, AUX, Tape1, 2 : 110 dB (-126dBV)
RIAA deviation	Within ± 0.2 dB
Phono maximum allowable input	150mV
Subsonic filter	15 Hz : -3dB, 6dB/oct. Incorporated into the phono equalizer (Non-filter for Phono Direct)
Input-output phase	Inphase However, only pre-out has both positive and reverse polarity outputs.
<General>
Circuit system	Shunt regulator type + reserve power supply
Power consumption	230W
External dimensions	Width 430x Height 165x Depth 485 mm
Weight	27kg