SANSUI AU - α 907 dr

Commentary

This pre-main amplifier is completed by carefully refining and combining the three factors of circuit, mechanism and parts.

The power stage adopts NM-LAPT (Non Magnetic Liner Amplification Power Transistor) developed as a power transistor exclusively for audio.
The NM-LAPT is made of pure copper material all the way up to the bonding wire, and realizes excellent high-frequency characteristics and high current limit value by manufacturing cut-off frequency (fT) and fracture resistance (PC).

Since the ground circuit of the power supply circuit is connected to the ground circuit of the amplifier circuit (negative output), we have introduced the original advanced α -X balance circuit to prevent the reverse current from the speaker side from flowing into the amplifier circuit and the deterioration of sound quality.
The amplifier circuit is completely independent from the ground circuit, and is balanced in such a way that transmission and amplification are carried out simultaneously, so that the circuit itself blocks out external noise and in-phase distortion.
The dynamic frequency characteristics are also improved by reducing the impedance of the circuit to minimize the influence on the passing signal.
In addition, a 4-amp configuration with dedicated amplifiers on the + side and - side each provides a push-pull system that drives from both directions under the same conditions on the + side and - side, thereby obtaining strong sound at a low distortion rate.

It further improves the perfection of the diamond actuation circuit in which - output can be taken out without phase inversion.
The cascade connection of the first stage FET realizes a wide range and high speed with excellent wide-area characteristics and greatly reduces the effect caused by impedance differences with external devices.

We have developed a new power transformer (IDEAL SILENT POWER TRANSFORMER) and a capacitor for power supply, and have succeeded in greatly improving power supply capability and stability.
Both primary and secondary transformers use OFC lead wires to minimize magnetic induction (リケージフラックス). The transformer weight is 13 kg because the shield is made of four layers of copper short rings, two layers of silicon steel plates and a squeeze case, high-density packing is used, and insulation materials are examined.
The electrolytic condenser and fast recovery diode have also been completely changed to the one exclusively for the highest sound quality.
All custom-made, low-impedance, clean NEW α -X balanced power supplies and a closed-loop configuration independent of ground minimize the negative effects of unbalanced power supplies on music signals.

The power supply unit is placed in the center and the power units are arranged symmetrically with the introduction of reinforced twin monaural construction. Each part with improved strength prevents sound quality degradation due to vibration, and acquires excellent sound image localization and phase characteristics.
In addition to vibration control by twin monaural construction, various components with high internal loss and vibration absorption effect are used abundantly, such as large insulators made of pure copper muku covered with felt, pure copper bases and copper-plated parts.
In addition, we have newly adopted the isolation of pure copper material, which has conventionally been used between the transformer and the chassis, between the electrolytic capacitor and the chassis, and between the amplifier base and the bottom plate, etc., between the master volume and the chassis, between the radiator and the power board, and even the transformer, electrolytic capacitor, power board, and power board itself.
As for the mounting structure of each part, for example, the case of the transformer is attached to the chassis instead of attaching the main body of the transformer directly to the chassis. We have succeeded in effectively blocking the transmission route of vibration by means of the opposed mechanical feedback.

In order to improve sound quality, the quality of each part is also thoroughly pursued.
In addition to the development of transformers and condensers, we have adopted rolled copper substrates for power boards and power supply boards, plated copper on rear panels, painted hoods with paint containing copper, and adopted bronze screws.
All parts are designed to be non-magnetic, vibration-proof, low impedance and high speed.

It is equipped with an input terminal that realizes high-purity transmission and amplification of digital sources by directly inputting audio signals to the power amplifier section.
Since there is a balanced input in addition to the normal input, setting by balance transmission and amplification is possible by connecting with an external device with a balanced output.

Equipped with a source power direct switch that transmits all line input signals directly to the power amplifier with one touch operation.
Connect and amplify directly without passing through any accessory functions to reproduce the pure sound of the source.

Equipped with a recording function for effective recording and listening when a CD player is connected to the Power Amp Direct.
For example, you can listen to the source input to Normal 1 while back-recording a CD or other source connected to Normal 2.

Equipped with all-gold plated input terminal, large speaker terminal, large insulator made of pure copper, real side wood, power cord / AC outlet with polarity display, etc.

Model Rating

Type	Integrated amplifier
Power Amplifier Unit
Rated output (20 Hz to 20 kHz Simultaneous operation on both channels, THD0.003%)	6 Ω : 190W + 190W 8 Ω : 160W + 160W
Total harmonic distortion factor	0.003% or Less (Rated Output, 20 Hz to 20 kHz, 8 Ω Load)
Frequency characteristic	DC ~ 300 kHz, + 0 -3dB (at 1W Output)
Cross modulation distortion factor	0.003% or Less (at 8 Ω Load)
Damping factor	150 (8 Ω)
Input Sensitivity / Impedance	1V/5k Ω (1 kHz)
Signal-to-noise ratio	120 dB or more (A network)
Dynamic Power	6 Ω : 310W 4 Ω : 390W 2 Ω : 580W
TIM (SAWTOOTH)	Measurement limit value or less
Slew rate	200 V / μ sec
Rise time	0.5 μ sec
<Pre-part>
Input Sensitivity / Impedance (1kHz)	Phono MM : 2.5mV/47k Ω Phono MC : 300 μ V/100 Ω CD, Tuner, Line, Tape/DAT1 / 2 / 3 : 150mV/20k Ω
Phono maximum allowable input	MM(THD 0.01%):250mV MC(THD 0.1%):25mV
Frequency Response (1W)	Phono MM : 20 Hz to 20 kHz, ± 0.2 dB CD, Tuner, Line, Tape/DAT-1 / 2 / 3 : DC ~ 300 Hz, + 0 -3dB
Signal-to-noise ratio (A network)	Phono MM : 90 dB or more Phono MC : 75 dB or more CD, Tuner, Line, Tape/DAT-1 / 2 / 3 : 110 dB or more
Tone control	Maximum variation of BASS : + / - 5 dB at 50 Hz Maximum change of TREBLE : ± 5 dB (15 kHz)
Subsonic filter	16 Hz (-3dB), 6dB/oct.
Loudness	50Hz:+4dB 10kHz:+3dB
<General>
Rated power consumption	400W
External dimensions	Width 460x Height 159x Depth 446 mm
Weight	33.0kg