NEC A-10TypeIII

Commentary

Based on the A-10TypeII, this pre-main amplifier has a stronger and more rigid structure and improved reserve power supply system.

The structure uses a unique mechanical ground construction.
In this system, the vibration of each part is completely suppressed by the material and structure, and the vibration of each part with different vibration modes is cancelled by each other in the whole structure by computer simulation. This simplified vibration is dropped on a huge leg and connected to the earth to suppress it.
The A-10TypeIII has been further strengthened and refined. It has a structure in which all mechanical vibrations are received by the legs with the occasional reference point of the set itself as the legs of the main body. Sintered alloy legs 50 mm in diameter and 22 mm in height are adopted for the insulators arranged in four places of the bottom plate.
In addition, a 3.2 mm thick steel plate is used for the bottom plate in order to securely connect the structural parts and power transformer to the legs.
In addition, a cross-beam is used to integrate the left and right side fittings, rear panel, and heat sink. The bottom and cross-beam are connected by four beams, and the core of the power transformer is securely fixed to the beams.
In addition, a chimney type heat sink is adopted to prevent fin squeal.
With this rigid structure, the main body and the ground are firmly grounded to eliminate the cloudy and cloudy sound caused by the relative relationship between the material and structure of the ground plane and the amplifier.
In addition to the normal 4-leg grounding, the insulator can be selected from 2 legs at the rear + 1 leg at the front and 1 leg at the rear + 2 legs at the front.

In order to approach the ideal image of the amplifier as "one wire with amplification degree", the Simple & Straight concept is adopted, and pure quality is realized by one contact direct connection in which all of attached circuits are jumped as necessary.
In order to enjoy the excellent dynamic range and high quality of digital sources such as CDs, it has a direct input to the power amplifier section.
In the A-10TypeIII, the quality improvement of the Phono series is re-examined. The EQ amplifier is equipped with DC servo, and the Phono direct position, which connects the Phono amplifier and the power amplifier directly with one contact by using a highly reliable relay, is installed.

The REC selector method allows you to record your favorite source regardless of the source being played.
In addition, a large vise type screw terminal is adopted to ensure the connection of a very thick speaker cord. This also enables the rear panel supporting the speaker terminal to be made of non-magnetic material. This eliminates magnetic material from the loop of the speaker output current and eliminates electrical disturbance.

The AC outlet is equipped with a line filter to prevent noise from entering and jumping.
This AC outlet operates unswitched and has polarity indication.

Signals recorded in commercially available CD software have both positive and reverse polarity.
The A-10TypeIII is equipped with a polarity inversion Pre Out terminal for reverse polarity software in order to manage the polarity of the entire system.
Reverse polarity By connecting the Pre Out and Main In with the attached U-shaped pin, the polarity can be reversed at the separate position of operation SW. This enables total polarity alignment.

The power supply section uses a large reserved power supply system.
In order to maintain a large output even when the capacitor is discharged, another power supply is prepared to compensate for the time when the charging current of the capacitor input type rectifier circuit does not flow. By delaying the phase of the output by 90 °, the ripple valley of the main power supply is filled, and it is equivalent to a battery power supply.
In addition, the A-10TypeIII has approximately 20% higher current capacity of the power transformer and capacity of the smoothing capacitor, and further lower power impedance, making it an even better power source.

A push-pull type amplifier circuit is used for all amplification stages, and superlinearity 2SA-1227 and 2SC-2987 utilizing NEC's semiconductor technology are used for the final amplification stage in parallel push-pull configuration.
By using output transistors in parallel, the effective halving of the emitter resistance, which enters the output current circuit in series, is avoided without loss of stability.
In addition, the output circuit is designed so that the protection by the ASO limiter is not necessary even with 2 Ω load. Therefore, the limiter that impairs the linearity of the output current does not operate even with 2 Ω load.

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	25kg