SANSUI AU-8500
¥ 118,000 (around 1973)
Commentary
This pre-main amplifier is designed with emphasis on sound quality and inherits the superior basic performance of the AU 9500, which was completed by pursuing basic performance to the utmost by making full use of Sansui's audio technology.
By making full use of carefully selected materials and specialized technology, stability in a wide playback band and low distortion rate in high-fidelity playback are achieved.
The circuit configuration is a constant current drive system for the pre-drive stage and a a direct-coupled OCL pure complimentary service system for all stages using a high-power, low-distortion parallel push-pull circuit for the output-stage.
A feature of the parallel push-pull circuit is that it can be used by selecting a part of the current characteristic of the power transistor with good linearity. In addition, it uses a large heat sinker so that heat radiation is expensive and stable operation with high output and low distortion rate can be obtained.
The power transistor and the pre-drive stage are provided with separate power supplies, and the pre-drive stage is driven by a high voltage.
In addition, the 3-stage Darlington connection of the drive stage enables stable driving regardless of load fluctuations.
The phase margin is one of the means to measure the stability of the amplifier. It is determined by how many degrees the phase is within the stability limit when the feedback gain of the amplifier itself is lost.
The AU 8500 has a sufficiently large phase margin not only in the ultra-low range but also in the ultra-high range to enhance stability and reliability under all load conditions from the equalizer to the main unit.
The equalizer circuit has a maximum allowable input of 300 mV using a 3-stage connected low-noise transistor and a high voltage supplied from + - 2 constant voltage power supplies.
The RIAA deviation is guaranteed to be ± 0.5 dB at 30 Hz to 15 kHz using low-noise transistors, low-error resistors, and capacitors.
Click noise generated during switching is prevented by using the + - power supply and setting the base potential of the first stage to 0.
The power supply section uses a large power transformer with good regulation and a capacitor of 15,000 μ Fx2 to supply a stable + - power supply.
This product uses a protection circuit that combines a relay and an electronic circuit and a double protection circuit that uses a short-cut fuse. In addition, a current limiter circuit is built in to prevent the collector current of the output stage and driver stage from exceeding a certain level due to overload. Together with four short-cut fuses, it protects the power transistor reliably.
The pre-out is equipped with a transient canceler circuit, and the relay circuit is also used as an audio muting circuit so that no unpleasant pop noise occurs when the power is turned on.
It uses a rotary switch with reliable operation and is equipped with T. T. C. (Triple Tone Control) which can be changed by ± 15 db in one step 3 db for low and high sound and by ± 5 db in 1 db step for medium sound.
The T. T. C. amplifier uses a low-noise FET with high input impedance at the first stage, and is an NF type with 3-stage and 2-stage direct-coupled circuits.
The frequency point of the middle adjustment can be switched between 750 Hz, 1.5 kHz and 3 kHz. It is also equipped with a defeat switch for flat characteristics.
A 12dB/oct. dedicated active filter circuit is used for the low / high filter.
The low filter has a cut-off frequency of 50 Hz, and the high filter has a cut-off frequency of 12 kHz. There is no waviness in the middle range.
There are two tape monitoring circuits. If you have two decks, you can tape reprint from either side and monitor during reprint.
Equipped with a 4-channel adapter circuit.
Noise reduction (N. R.) adapter connection circuit is mounted.
Equipped with a muting switch with 20 dB attenuation.
Equipped with 5 position mode selectors : Stereo Reverse, Normal, Mono L + R, L, R.
It is equipped with a loudness switch.
There are 2 types of headphone jacks, and one of them can turn off the sound of the speaker.
The speaker system is Route 3 connectable.
The input impedance of Phono2 can be changed to 30k Ω, 50k Ω or 100k Ω.
The Deck1, Deck 2 and Deck AUX have level adjusters that enable you to unify the input levels.
High-impedance microphone input terminal.
Equipped with 4 AC outlets.
It uses a smooth touch of pure aluminum knob.
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Model Rating
| Type | Pre-main amplifier | ||||||
| Rated output (rated distortion factor) |
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| Music Power (IHF) | 240W (4 Ω, 1 kHz) 180W (8 Ω, 1 kHz) |
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| Total harmonic distortion factor (rated output) | Preamplifier section : 0.05% or less Main amplifier : 0.1% or less Total : 0.1% or less |
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| Cross modulation distortion factor (rated output) | Preamplifier section : 0.05% or less [70 Hz : 7 kHz = 4 : 1, SMPTE] Main amplifier : 0.1% or less Total : 0.1% or less |
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| Power Band With | 5 Hz ~ 40 kHz (IHF, Rated Distortion Factor) | ||||||
| Frequency response (at 1W output) | Main Amplifier Section : 3 Hz ~ 50 kHz, + 0 -1dB General : 15 Hz to 30 kHz, + 0.2 dB -1dB |
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| RIAA deviation | 30 Hz to 15 kHz, ± 0.5 dB (Phono1, 2) | ||||||
| Load impedance | 4 Ω ~ 16 Ω | ||||||
| Damping factor | 50 (8 Ω) | ||||||
| Input Sensitivity / Input Impedance (1kHz) |
Phono1 : 2.5mV/50k Ω Phono2 : 2.5mV/30k Ω, 50k Ω, 100k Ω [Maximum allowable input 300 mV, total harmonic distortion rate 0.5% or less] MIC : 2.5mV/50k Ω Tuner, AUX (level adjustable) : 100mV/50k Ω Tape Monitor1, 2 (PIN) (level adjustable) : 100mV/50k Ω Tape Monitor2 (DIN) : 100mV/50k Ω 4 ch, N. R. Adaptor : 100mV/50k Ω Main Amp : 800mV/50k Ω |
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| Output Voltage / Output Impedance | Tape Rec1, 2 (PIN) : 100mV/1.5k Ω Tape Rec2 (DIN) : 30mV/70k Ω 4 ch, N. R. Adaptor : 100mV/1.5k Ω Preamplifier (Rated Output) : 0.8V/1.5k Ω Maximum output, 0.5% or less total harmonic distortion : 5 V |
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| Crosstalk (rated output 1 kHz) | Phono1, 2, MIC : 50 dB or more Tuner, AUX : 50 dB or higher Main Amp : 60 dB or higher |
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| Hum and noise (IHF) | Phono1, 2 : 75 dB or more MIC : 65 dB or higher Tuner, AUX : 85 dB or higher Main amplifier : 100 dB or more |
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| Tone control | Bass : ± 15 dB (20 Hz), 3 dB step Midrange (Defeat, 750 Hz, 1.5 kHz, 3 kHz) : ± 5 dB (1.5 kHz), 1 dB step Treble : ± 15 dB (20 kHz), 3 dB step |
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| Loudness (volume -30dB) | 50Hz:+10dB 10kHz:+8dB |
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| Low filter | 50Hz:-3dB(12dB/oct) | ||||||
| High filter | 12kHz:-3dB(12dB/oct) | ||||||
| Semiconductor used | Transistor : 58 FET:2 Diode : 33 Zener diode : 5 |
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| Rated power consumption | 140W (up to 450 VA) | ||||||
| External dimensions | Width 500x Height 140x Depth 347 mm | ||||||
| Weight | 20.5kg |