SONY TA-N7B
¥ 160,000 (around 1977)
Commentary
A power amplifier that pursues low crosstalk and high quality by using carefully selected semiconductors such as V-FET and applying technologies such as FET buffer power supply.
A DC amplifier configuration is adopted, and since there is no capacitor that forms the time constant of the amplifier circuit, phase rotation in the low range is eliminated, and phase distortion is suppressed.
The TA-N7B solves the stability problem of the DC amplifier by suppressing DC drift with the dual FET created by Sony's semiconductor technology.
Differential amplification cascode connection is used for the voltage amplification stage of the A-class stage.
Since the cascode connection suppresses the mirror effect caused by the feedback capacitance of the output side, it prevents the lowering of the transmission capability at the high frequency and greatly improves the linearity.
In the power amplifier stage, which is a class B stage, a V-FET and a bipolar transistor are cascode-connected to obtain excellent characteristics and stability.
The power supply section employs a high-efficiency rectangular toroidal transformer with an oriented core for each B-class stage, a multi-tab electrolytic capacitor with a total capacity of 88,000 μ F, and a power supply transformer exclusively for the left and right sides for A-class stage.
In addition, the FET buffer power supply circuit that reduces noise distortion caused by the power supply realizes low crosstalk.
It is constructed with structural and electrical considerations such as adopting a symmetrical two mono-amplifier configuration, greatly eliminating accessory functions, and completely shielding the signal path.
As a result, channel separation characteristics exceeding the measurement limit value are obtained.
The triple-protection circuit greatly improves reliability and safety.
A die-cast frame is used for the front panel and an air intake is provided.
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Model Rating
| Type | DC power amplifier |
| Effective output (20 ~ 20 kHz, both channels) | 100W + 100W (8 Ω) |
| Output Bandwidth (IHF, 8 ω) | 5 Hz to 35 kHz |
| Harmonic distortion factor | 0.01% (20 Hz to 20 kHz at effective output) |
| Cross modulation distortion factor (at effective output) | 0.01% |
| Frequency characteristic | Direct Terminal : DC ~ 100 kHz + 0 -1dB C. Coupled terminal : 6 Hz to 100 kHz + 0 1 dB |
| Signal-to-noise ratio | 120dB |
| Damping factor (1 kHz, 8 Ω) | 100 |
| Input sensitivity | 1.3 V (50k Ω at effective output) |
| Power consumption | 215W |
| External dimensions | Width 430x Height 170x Depth 335 mm |
| Weight | 21kg |