Aurex SB-820
¥ 135,000 (around 1976)
Commentary
A stereo pre-main amplifier with wide range and low distortion.
The main amplifier section has two stages of first stage cascade connected differential amplifier, and all stages are directly connected pure complimentary service OCL circuit with improved and stabilized dynamic characteristics. In addition, the 3-stage directly connected Darlington driver stage is driven by constant current, greatly reducing distortion in case of small signal.
The output stage is a single push-pull drive using a transistor with high collector loss and margin.
The equalizer circuit of the pre-amplifier section uses a 2-stage differential active class A operation circuit and a high voltage of ± 70 v to obtain a high allowable input. The RIAA element uses a high-precision metal film resistor and a plastic film capacitor to obtain an excellent characteristic of ± 0.2 dB deviation.
In addition, noise and unstable operation are eliminated by increasing the S / N ratio with low-noise transistors in all stages, installing ± 2 low-voltage power supply circuits, and using separate pre-windings for power transformer windings.
The tone amplifier section adopts NF type of 2-stage direct connection active broad including one stage differential using FET.
This circuit also uses a highly stable ± 2 power supply.
A large cut core transformer and 15,000 μ Fx2 electrolytic capacitor are used in the power supply section.
It is equipped with duplicate switch which can use 3 tape decks.
It is equipped with a muting circuit that disconnects the speaker terminals until the circuit stabilizes after the power is turned on.
It is also equipped with an automatic recovery relay protection circuit that protects the speakers and transistors.
The volume part uses a high-precision attenuator type volume with less gang error.
Mutual deviation and step deviation of this volume are suppressed to ± 0.2 dB.
Data sheet of actual measurement is attached.
Seven items are listed : input sensitivity (Phono, Aux), continuous output, harmonic distortion factor, SN ratio, Phono maximum allowable input, frequency-distortion factor characteristics, and RIAA deviation.
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Model Rating
| Type | Pre-main amplifier | ||
| Circuit system | Pure complimentary service OCL circuit directly connected to all stages | ||
| Power Amplifier Unit | |||
| Output (both channel drive) |
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| Harmonic distortion factor | 0.1% or Less (Continuous Output) 0.05% or Less (at 1W Output) |
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| Cross modulation distortion factor | 0.1% or Less (Continuous Output) 0.05% or Less (at 1W Output) |
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| Output Bandwidth (IHF) | 6 Hz ~ 100 kHz (8 Ω) | ||
| Damping factor | 40 (8 Ω, 1 kHz) | ||
| Residual noise | 0.3mV | ||
| Preamplifier Section | |||
| Input Sensitivity / Impedance | Phono1 : 2.0mV/50k Ω Phono2 : 2.0mV/47k Ω, 100k Ω Aux, Tuner, Tape : 150mV/50k Ω |
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| Recorded output | Tape rec:150mV Din:30mV |
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| Equalizer allowable input | MAG:600mV(RMS) | ||
| RIAA deviation | + / - 0.2 dB | ||
| Signal-to-noise ratio (IHF) | Phono:73dB Aux:90dB |
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| Harmonic distortion factor | 0.01% (Continuous Output) | ||
| Frequency characteristic | 10 Hz to 50 kHz -1dB | ||
| Tone control |
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| Muting | -10dB, -20dB | ||
| Filter | Low : 30 Hz, 10 Hz, 12dB/oct. High : 8 kHz, 20 kHz, 12dB/oct. |
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| <General> | |||
| Semiconductor used | Transistor : 64 Diode : 29 units LED : 4 pcs |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||
| Power consumption | 215W | ||
| External dimensions | Width 450x Height 148x Depth 375 mm | ||
| Weight | 16kg | ||
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