SANSUI AU-5900
¥ 53,000 (around 1976)
Commentary
A pre-main amplifier developed based on the same concept as AU 7900.
The power amplifier section uses a pure complimentary service circuit directly connected to all stages.
The first stage dual transistors is adopted for the first stage, and Darlington 3-stage configuration with active broad is adopted for the drive stage. In addition, the power supply for the pre-drive stage is separated from the power supply for the output stage. This improves linearity and reduces the occurrence of non-linear distortion even when a transient signal enters.
The equalizer uses an NF-type equalizer circuit consisting of four low-noise transistors. The first stage input is a differential amplifier with a good DC balance. The + / - 2 power supply with a total high voltage of 51 v is supplied in a well-regulated manner to ensure a sufficient margin.
A carefully selected CR element is used for the equalizer element.
The Phono1 input allows 3-step switching of impedance.
The input terminal on the back has a unique structure in which terminals are mounted upward.
With this structure, it is not necessary to use a shield wire from the input terminal to the selector, and degradation of high-frequency characteristics due to stray capacitance can be prevented.
The preamp section and main amplifier section can be separated by a switch on the back panel.
Low-noise transistors and high-precision CR elements are used in the tone control circuit. These parts and switches are directly attached to a single board in an integrated structure to prevent lead wires and shield wires from being routed. The circuit configuration is NF type, degradation of sound quality.
The tone control is a triple tone control unique to SANSUI, and you can also adjust the sound quality in the middle range.
Equipped with a tone defeat function.
In defeat mode, the tone control and filter circuits are bypassed, and the signal from the buffer amplifier after the volume is fed directly to the main amplifier.
The power supply section uses a large power transformer and combines a silicon diode for rectification and a 10,000 μ Fx2 large-capacity power supply capacitor to provide ample room.
In addition, this large power supply unit supplies a stabilized power supply to all block stages except for the power stage and drive stage, and supplies ± 2 power supply with good regulation and strong resistance to load fluctuation at the time of Dainyu force.
As a protective circuit, an output terminal DC detection circuit combining an electronic circuit and a relay, an abnormal temperature detection circuit, and an ASO (safe operating area) detection current limiter circuit are mounted.
By adopting a chassis-less structure and a one point grounding system in which a power transformer is installed independently, the deterioration of sound quality is reduced.
A spare AC outlet is installed.
Equipped with a loudness control.
Equipped with low filter and high filter.
Equipped with a muting function.
The stereo/mono mode can be switched with the mode selector switch.
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Model Rating
| Type | Pre-main amplifier | ||
| Effective power |
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| Total harmonic distortion factor | 0.1% or Less (at Rated Output) 0.08% or Less (at 1/2 Output) |
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| Cross modulation distortion factor | 0.1% or less (70 Hz : 7 kHz = 4 : 1, SMPTE) | ||
| Power Band With (IHF) | 5 Hz ~ 40 kHz (8 Ω) | ||
| Frequency Response (at 1W) | 10 Hz ~ 50 kHz + 0 -1.5 dB | ||
| RIAA deviation | 30 Hz to 15 kHz ± 0.3 dB | ||
| Damping factor | 80 (8 Ω) | ||
| Channel Separation (1 kHz) | Phono1, 2 : 50 dB or more Aux1, 2, Tuner, Tape1, 2 : 55 dB or more Power amp : 60 dB or higher |
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| Hum and noise (IHF) | Phono1, 2 : 75 dB or more Aux1, 2, Tuner, Tape1, 2 : 90 dB or more Power amp : 100 dB or higher |
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| Phono maximum allowable input | 250 mv (1 khz, THD0.1% or less) | ||
| Input Sensitivity / Impedance (1 kHz) | Phono1 : 2.5mV/30k Ω, 50k Ω, 100k Ω Phono2 : 2.5mV/50k Ω Aux1, 2, Tuner, Tape1, 2 (PIN) : 130mV/50k Ω Tape1(DIN):130mV Power amp : 700mV/50k Ω |
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| Recorded output | Tape rec1, 2 (PIN) : 130 mV Tape rec1(DIN):30mV |
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| Tone control | Bass : ± 13 dB (50 Hz) Midrange : ± 5 dB (1.5 kHz) Treble : ± 13 dB (15 kHz) |
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| Loudness | + 8 dB at 10 kHz, + 10 dB at 50 Hz | ||
| Low filter | -3dB, 70 Hz (6dB/oct.) | ||
| High filter | -3dB, 7 kHz (6dB/oct.) | ||
| Muting | 0 dB, -20dB | ||
| Power consumption | 106W (rated) 300W maximum |
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| External dimensions | Width 430x Height 132x Depth 312 mm | ||
| Weight | 11.5kg |