SANSUI AU - α 907

Commentary

Integrated amplifier with α -X balanced circuit.

The power amplifier section uses SANSUI's unique α -X balanced circuit.
In the α -X balanced circuit, the signal circuit, the power supply circuit, and the NFB circuit completely separate the signal from the earth, eliminating the IHM distortion. Furthermore, the balance amplifier in the pre-part enables the α -X balanced transmission of not only the α -X balanced input but also the normal input.
In this circuit, the + and - sides of the speakers are each driven by a dedicated amplifier, so the speaker movement can be controlled by the amplifier.

The power supply section uses an α - X balanced power supply that supplies energy independently of the ground. This eliminates noise from the AC line and prevents unbalanced and ripple currents from flowing into the speakers. In addition, the power supply system separates the power stage from the voltage amplification stage to eliminate mutual interference.
A sealed ultra-large power transformer and a Great Pure Focus / HS condenser are used for the power transformer to ensure stable energy supply.

Power Amp Direct is installed and the input signal can be directly connected to the power amp.
Two systems are provided for the direct terminal : a normal terminal and a balanced input.

A specially developed 6-string master volume is used for the volume.
This volume consists of two pre-main amplifiers (impedance 50k Ω) and four low-impedance direct position amplifiers (impedance 5k Ω), making it possible to transmit and amplify sound without losing sound quality.
The scale shows for premain and direct position respectively.

The internal structure uses twin mono construction in which left and right channels are separated, eliminating mutual interference between channels.
The power transistor is mounted on the lower part of the power amplifier board to reduce the adverse effects of vibration and noise generated by the power transistor. The heat sink with the power block fixed is fixed to the solid chassis via dump material to reduce the adverse effects of vibration.

A newly developed solid chassis is used for the chassis structure.
In the solid chassis, a high-rigidity separator is installed on the front and both sides with a space between the external panel. Inside the external case, there is an internal case that protects the parts. In addition, a separator that connects the hood of the internal case and the insulator directly is installed to prevent mutual interference within the amplifier.
As a result, the structure of the whole amplifier is made highly rigid from the inside to prevent vibration in vertical and horizontal directions. In addition, the separator of the solid chassis is made of high conductivity material with high shielding effect, and excellent shielding effect is obtained.

CF5 (Chassis Fixed 5-point Support) insulator is used for the legs.
Unlike conventional insulators, which were fixed to the bottom plate, the CF5 insulator is fixed directly to the solid chassis, so the bottom plate is fixed firmly and overall rigidity is increased.
In addition, five large insulators are used by equalizing the load applied to the insulators, five large insulators are used. A fifth compliant insulator is placed near the power supply part where the weight is concentrated to balance the load and realize mechanical grounding.

It uses a CF12 (chassis fixed, 12-point) bonnet.
In the CF12 bonnet, the U-shaped rigid bonnet determined from the results of vibration analysis is fixed to a solid chassis using 12 screws, which are much larger than conventional ones, to suppress resonance and vibration.

The phono equalizer has a discrete configuration using carefully selected parts and consists of two stages of FET differential and five stages in total.

In pursuit of musical performance, we avoid overusing printed circuit boards and actively use wires in signal, power, and ground systems to prevent crosstalk and achieve high conductivity.

Equipped with a source direct function, all sources can be directly connected to the α -X balance circuit without passing through an accessory circuit, and the tone control can also be used for source direct.

Equipped with a tone control with defeat.
This tone control allows you to change the turnover frequency.

Gold plated terminals are used for the Phono, CD, Tape/DAT-1 and Power amp direct (Normal) terminals.

Uses a power cord with polarity display.

Equipped with a REC selector with OFF position.

The front panel is a glossy & hairline finish made of aluminum material.

Model Rating

Type	Integrated DC amplifier
Power Amplifier Unit
Effective output (10 Hz to 20 kHz, both channels driven)	190W + 190W (6 Ω) 180W + 180W (8 Ω)
Total harmonic distortion factor (at effective output)	0.003% or Less (8 Ω)
Cross modulation distortion factor	0.003% or Less (8 Ω)
Damping factor	100 (6 Ω)
Frequency Response (1W)	DC ~ 300 khz + 0 -3dB
Input Sensitivity / Impedance (1 kHz)	Normal : 1V/5k Ω Balance : 1V/5k Ω
Signal-to-noise ratio (A network)	120 dB or more
TIM (SAWTOOTH)	Below the measurement limit
Slew rate	± 200 V / μ sec
Rise time	0.5 μ sec
Equalizer Section
Input Sensitivity / Impedance (1 kHz)	Phono MM : 2.5mV/47k Ω Phono MC : 300 μ V/100 Ω CD, Tuner, Line, Processor : 150mV/47k Ω Tape play/DAT-1, 2, 3 : 150mV/47k Ω
Phono maximum allowable input (New IHF, THD 0.01%)	MM:210mV MC:21mV
Frequency Response (at 1W)	Phono MM : 20 Hz to 20 kHz ± 0.2 dB CD, Line, Tape play/DAT-1, 2, 3 : 1 hz ~ 300 khz + 0 -3dB
SN ratio (at 1W)	Phono MM : 88 dB or more Phono MC : 70 dB or more Tuner, Line, CD : 110 dB or higher Tape play/DAT-1, 2, 3 : 110 dB or more
Tone control	Bass : + / - 5 dB (50 Hz) Treble : ± 5 dB (15 kHz)
Turnover frequency	75 hz, 150 hz, 7 khz
Subsonic filter	16 Hz (-3dB, 6dB/oct.)
Loudness	+ 8 dB at 50 Hz, + 6 dB at 10 kHz
<General>
Rated power consumption (Electrical Appliance and Material Control Law)	370W
External dimensions	Width 448x Height 160x Depth 441 mm
Weight	28.0kg