Audio Database

Image of A-0012
Commentary

A pre-main amplifier developed with new elements and new circuits to realize the "Magniwide power range" concept of full power reproduction at low distortion rate over an ultra-wide band.

The A-0012 uses a group transistor RET with superior high-frequency switching characteristics. This device is made by combining hundreds of small transistors with superior high-frequency characteristics in parallel. It has high breakdown strength and can produce high output at high frequencies with low distortion.
In addition, a DC amplifier configuration has been adopted to improve the low-frequency characteristics, extending the frequency characteristics to the ultra-low frequency range and improving the phase characteristics in the mid-low frequency range.

The power supply consists of a large left and right independent transformer with an emphasis on dynamic characteristics and a 18,000 μ Fx4 capacitor.
In addition, the power section through which a large current flows and the speaker terminals are wired on extremely thick Line 14 with a resistance value that is 1/4 of the conventional thick line. In addition, pure copper is used for the ground line of the power capacitor, and at the same time, the copper foil on the printed circuit board of each circuit is doubled to 70 μ thick, making for a thorough low-impedance design.

It uses class AB operation and operates up to 3W, which accounts for most of the music signal, at class A, which has an established reputation for sound quality, with essentially no switching distortion or crossover distortion.
In addition, since the power utilization factor is high efficiency close to that of general class B amplifiers, it is possible to obtain a dynamic range of up to 120W during peak playback.

It has a 4 dc configuration consisting of an MC head amplifier, an equalizer amplifier, a flat amplifier, and a power amplifier. If a buffer amplifier is included, it can be called a 5 dc amplifier.
Since all amplification stages are DC, there is no capacitor that causes phase distortion in the NFB loop of the amplifier circuit, and it has flat phase characteristics over a wide band and stable operation. It also improves transient response characteristics including the damping of back electromotive force from the speaker.

In the equalizer amplifier section, a low-noise dual FET with excellent noise characteristics is used in the first stage differential section.
In the dual FET, the entire element has a high SN ratio, and at the same time, a higher SN ratio is obtained by suppressing the voltage between the drain and gate of the FET by cascade connection to prevent generation of noise.

The whole MC head amplifier section is divided into two systems. The first stage parallel connection symmetrical 3-stage direct-coupled A-class SEPP-DC amplifier is composed of two newly developed low-noise NPN and PNP transistors connected in parallel. It is designed to improve linearity when NFB is not applied by focusing on bare characteristics.
In addition, the SN ratio is improved by adopting symmetrical circuit configuration.

All stages of the flat amplifier section are DC to improve sound quality.
In addition, a flat amplifier and bypass switch are installed in order to pursue higher purity playback sound. By jumping from a flat amplifier, a buffer amplifier and a power amplifier can be connected directly.

Equipped with a change-over switch that can independently select 5 types of load resistance and 5 types of load capacity and can set a total of 25 types of cartridge load.

In addition to the main control of the standard bass / treble, it is equipped with a twin-tone control with an ultra-low and ultra-high range control knob as a sub-control.
It is also equipped with a tone ON-OFF switch that can obtain flat characteristics by bypassing the tone control circuit.

Equipped with a subsonic filter that allows slope switching.

The volume uses a continuously variable precision volume of decibel display with excellent corrosion resistance gold-plated sliding elements and terminals.

The Phono terminal is gold-plated.

Equipped with audio muting.

A dedicated parent-child contact relay for each of speakers A and B is used for the protection circuit.

Equipped with split switches for pre-part and power part, can be used separately.

Model Rating
Type Stereo pre-main amplifier
Power Amplifier Unit
Effective output (both channel drive, 8 Ω) 120W + 120W (5 Hz ~ 30 kHz, THD 0.01%)
120W + 120W (5 Hz to 100 kHz, THD 0.05%)
Harmonic distortion factor 0.01% (Effective Output, 5 Hz to 30 kHz, 8 Ω)
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1) 0.002% (8 Ω at effective output)
Output Bandwidth (IHF, double-channel drive, 8 ω) 5 Hz ~ 40 kHz (THD 0.01%)
5 Hz ~ 100 kHz (THD 0.05%)
Frequency response (at 1W output) 5 Hz to 50 kHz + 0 -1dB
Damping factor 70 (5 Hz ~ 30 kHz, 8 Ω)
Signal-to-noise ratio 120 dB (IHF, A-network, short circuit)
Preamplifier Section
Input Sensitivity / Impedance Phono1, 2 (MM) : 2.5mV/100 Ω, 10k Ω, 25k Ω, 50k Ω, 100k Ω
Phono1, 2 (MC) : 250 μ V/100 Ω
Tuner, Aux, Tape play1, 2 : 150mV/50k Ω
Cartridge load capacity Phono1, 2 (MM) : 100 pF, 200 pF, 300 pF, 400 pF, 500 pF
Phono maximum allowable input
(1 kHz, 0.01% THD)
MM:300mV
MC:30mV
Harmonic distortion factor (5 Hz to 30 kHz) 0.005% (1 V Output)
0.01% (15 V Output)
Frequency characteristic Phono : 20 Hz to 20 kHz ± 0.2 dB
Tuner, Aux, Tape play : 5 hz to 300 khz + 0 to 1 db
Signal-to-noise ratio (IHF, A-network
Short circuit)
Phono MM:91dB
Phono MC:80dB
Tuner, Aux, Tape play : 100 dB
Subsonic filter 15 Hz, 6dB/oct., 12dB/oct.
Flat amplifier bypass -20dB
<General>
AC outlet Power switch interlock : 2 systems
Power switch not linked : 2 systems
Power supply voltage 100 VAC, 50Hz/60Hz
Power consumption 400W (Electrical Appliance and Material Control Law)
980W maximum
External dimensions Width 454x Height 167x Depth 468 mm
Weight 24.7kg