SANSUI AU - α 707i

Commentary

Stereo pre-main amplifier with α -X balanced circuit.

The α -X balanced circuit uses an independent amplifier for both the + side and the - side of the signal to transmit and amplify it. Since it is separated from the ground, the effect of noise and distortion from the ground is prevented in principle.
In addition, the input stage of the power section is a differential balance input using a low-noise FET, and the common-mode rejection ratio CMRR (Common Mode Rejection Rato) between the + side and - side of the signal system is large, so that the circuit itself cancels common-mode noise and distortion.
In addition, while conventional amplifiers drive between the output of the amplifier and the ground, the α -X balanced circuit drives from both the + and - sides. This eliminates power supply noise and prevents IHM (Interface Hum Modulation) from occurring due to back electromotive force from the speakers.

The power supply section uses a unique balanced power source that is independent from the ground and closed loop.
The current is always equal between the + side and the - side, which prevents adverse effects on the signal due to unbalanced power supply and is also resistant to noise from the AC line and power supply fluctuations.
In addition to a large transformer with high capacity and excellent regulation, it also employs a Great Pure Focus capacitor with fast charge / discharge speed, a custom power supply capacitor with a gold supply capacitor, and a high-current capacity fast recovery diode.

In addition to the master regulator, we have adopted a twin regulator system in which local regulators are placed on the phono equalizer board and preamplifier board.
The 2-stage regulator is resistant to fluctuations in power supply and load, enabling a stable and clean power supply.

A board is used for the board of the power section to cut off the minute vibration of the board.

A solid and anti-flux chassis designed to eliminate vibration and noise interference is used. Each stage is completely separated and shielded by a separator, and five large insulators (CF5 insulators) with optimum load distribution are used to prevent external vibration.

The volume employs a high-precision 6-row detent type volume with little sound quality degradation and small left-right interlocking error. It can be narrowed down to around -90dB and the SN ratio on the mounting is improved.

A phono equalizer of FET configuration is used.

Equipped with a balance input capable of more accurate balance transmission and amplification and a power amplifier direct function.

Equipped with a source direct function that passes accessory circuits of subsonic filter, muting and balance control and connects all input sources directly to the pre-drive stage.

Model Rating

Type	Α -X balanced integrated amplifier
Power Amplifier Unit
Rated output (10 Hz to 20 kHz Both channel drive)	160W + 160W (6 Ω) 130W + 130W (8 Ω)
Total harmonic distortion factor (at effective output)	0.003% or Less (8 Ω)
Cross modulation distortion factor (at effective output)	0.003% or Less (8 Ω)
Damping factor	150 (8 Ω)
Frequency Response (1W)	DC ~ 300 khz + 0 -3dB
Input Sensitivity / Impedance	Balance, Normal : 1V/3k Ω (1 kHz)
Signal-to-noise ratio (A network)	120 dB or more
TIM (SAWTOOTH)	Measurement limit value or less
Slew rate	± 200 V / μ sec
Rise time	0.5 μ sec
Preamplifier Section
Input Sensitivity / Impedance (1kHz)	Phono MM : 2.5mV/47k Ω Phono MC : 300 μ V/100 Ω CD, Tuner, Line, Prossesor, Tape/DAT/Play1 ・ 2 ・ 3 : 150mV/47k Ω
Phono maximum allowable input	MM:210mV(THD 0.01%) MC:21mV(THD 0.1%)
Frequency characteristic	Phono MM : 20 Hz to 20 kHz ± 0.2 dB CD, Line, Tape/DAT/Play1 / 2 / 3 : 1 hz ~ 300 khz + 0 -3dB
Signal-to-noise ratio	Phono MM : 88 dB or more Phono MC : 70 dB or more Tuner, Line, CD, Tape/DAT/Play1 / 2 / 3 : 110 dB or more
Tone control	Maximum variation of Bass : ± 5 dB (50 Hz) Maximum variation of Treble : ± 5 dB (15 kHz) Turnover frequency : 75 Hz, 150 Hz
Subsonic filter	16 Hz (-3dB), 6dB/oct.
Loudness	50Hz:+6dB 10kHz:+4dB
<General>
Rated power consumption	320W
External dimensions	Width 448x Height 160x Depth 441 mm
Weight	20.5kg