Audio Database

The

SANSUI AU-alpha 707i
129,000yen(1987 release)

Description
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The stereo Integrated Amplifier which adopted the alpha-X balance circuit.

An alpha-X balance circuit is a scheme transmitted and amplified using the exclusive amplifier which became independent to both by the side of + of a signal, and -, and since it has dissociated with the grounding, it has prevented the noise and the distorted influence from a grounding theoretically.
Moreover, the power part input stage is considered as the differential balance input which uses low-noise FET, and since inphase component removal ratio:CMRR (Common Mode Rejection Rato) by the side of + of a signal system and - is large, the circuitry itself has canceled an inphase noise and distortion.
Furthermore, in order to drive from the bothways by the side of + and - to the conventional amplifier having driven between the amplifier output and the grounding in an alpha-X balance circuit,A power supply system noise did not mix but the occurrence of IHM (Interface Hum Modulation) by the counter-electromotive force from a speaker is prevented.

The original balance power source which was made to become independent of a grounding and was made into the closed loop is used for a power-source part.
+ While an electric current is equal and always prevents the ill effect to the signal by the unbalance of a power source by the side and - side, it is a design strong also against the noise and power supply variation from AC line.
Moreover, while carrying the mass large-sized transformer excellent in the regulation, the custom-made power source capacitor of a great pure Focus capacitor and a gold supply capacitor with a quick charge-and-discharge speed and large-current capacity first recovery diode are adopted.

In addition to a master regulator, the twin regulator system which has stationed the local regulator on a phone equalizer substrate and a preamplifier substrate is adopted.
For the regulator of a two-step stream composition, it is strong to a power supply variation or a load variation, and the stable clean powering is made possible.

The De Dis Pau Shal substrate which cuts a detailed oscillation of a substrate is adopted as the substrate of a power part.

The solid & anti flux chassis which the work which eliminates an oscillation and an interference of a noise was made is used for the chassis. While carrying out the full separation shielding of each stage with a separator, measures are taken also against the extraneous vibration by five large-sized insulators (certain-factor5 insulator) by which loading distribution was carried out the optimal.

A volume has little tone-quality failure, it has adopted the small high precision 6-unit Detent type volume of a right-and-left interlock error as it, it can narrow down to it to near -90dB, and the SN ratio on a package is improved.

The phone equalizer of an FET stream composition is adopted.

The balance input in which higher-precision balance transmit and amplification are possible, and the power amplifier direct functionality are carried.

A Subsonic Filter, a muting, and the accessories circuitry of a balance control are passed, and the Source-Direct functionality which links all the input sources with the predrive stage directly is carried.

Power-source De
Phase-correction 6-unit

Rating of a mode
Form Alpha-X balance integrated amplifier
<Power amplifier part>
Output power (10Hz - 20kHz)
Both channel drive
160W+160W (6ohm)
130W+130W (8ohm)
THD (at the time of an effective output) 0.003% or less (8ohm)
Cross modulation distortion (at the time of an effective output) 0.003% or less (8ohm)
Dumping factor 150 (8ohm)
Frequency characteristic (1W) DC-300kHz+0 -3dB
Input sensitivity/impedance Balance, Normal:1V/3kohm (1kHz)
SN ratio (A network) 120dB or more
TIM distortion (SAWTOOTH) Below a limit-of-measurement value
Slew rate }200v/microsec
Rise time 0.5microsec
<Preamplifier part>
Input sensitivity/impedance
(1kHz)
Phono man month: 2.5mV / 47kohm
Phono MC: 300 microvolts/100 ohm
compact disk, Tuner, Line, Prosessor, Tape/DAT/Play1-2-3:150mV /, 47kohm
Phono maximum permissible input MM:210mV(THD 0.01%)
MC:21mV(THD 0.1%)
Frequency characteristic Phono man month: 20Hz-20kHz}0.2dB
compact disk, Line, and Tape/DAT/Play1-2-3:1Hz-300kHz+0 -3 dB
SN ratio Phono man month: 88dB or more
Phono MC: 70dB or more
Tuner, Line, compact disk, and more than Tape/DAT/Play1-2-3:110dB
Tone control The Bass maximum variation: }5dB (50Hz)
The Treble maximum variation: }5dB (15kHz)
Turnover frequency: 75Hz, 150Hz
Subsonic Filter 16Hz (-3dB), 6dB / oct
Loudness 50Hz:+6dB
10kHz:+4dB
<Synthesis>
Power dissipation 320W
Dimensions Width 448x height 160x depth of 441mm
Weight 20.5kg