SANSUI AU-D907X

Commentary

Integrated amplifier with X-balanced amplifier.

The basic configuration of the AU-D907X amplifier is an X balanced amplifier.
The X balance amplifier consists of six technologies : a differential balance input configuration, a balance output configuration, a balance feedback configuration, a balance power supply system, a balance current drive configuration, and a twin diamond balance differential circuit. The transmission and amplification system is completely separated from ground by using all of the input, output, power supply, and feedback as a balance amplifier.

The output stage is balanced by two sets of Darlington output stage and differential push-pull amplifier stage.
The balanced output stage with two amplifiers drives the speakers equally from the + side and the - side. This eliminates the sound quality degradation caused by grounding, which is a problem in single-drive systems, and minimizes distortion of the circuit itself.
In addition, it has a balanced feedback configuration in which NFB is applied to each of the two amplifiers of the balanced output stage, and distortion and characteristics during actual operation are greatly improved.

The input stage has a differential balanced input, so that the input differential stage has a high CMRR (Common Mode Rejection Ratio) of 90 dB, and the differential input is only affected by 1/30,000 of the ground, making clean input possible.

The pre-drive stage employs a twin diamond balance differential circuit utilizing a diamond differential circuit.
This circuit is based on the fact that the diamond differential circuit originally has four outputs. We have succeeded in balanced push-pull driving of two pairs of output stage amplifiers using four outputs.
Although this circuit is a differential circuit without a constant current source, its differential operation is complete and it boasts very high stability. It also realizes excellent dynamic characteristics by taking advantage of the high-speed response of the diamond differential circuit and the sufficient supply of operating current required inside the amplifier.

In order to realize a non-earth amplifier, current transmission independent of earth is required for signal transmission, so we use a twin diamond balance differential circuit for voltage-to-current conversion to realize balanced current transmission.

The power supply section has a balanced power supply configuration.
Balanced power supplies are grounded completely, and there is no center tap, which is essential for conventional power supplies, so there is no unbalanced or ripple current flowing into the speakers.
In addition, the power supply configuration is completely closed loop so that the current supplied to the amplifier and the back electromotive force from the speakers are independent of the signal, so that IHM distortion which is harmful to sound quality is not generated. In addition, the noise component contained in the household power supply (100 v) is canceled due to the balanced power supply configuration so that it is not mixed into the amplifier.
The power supply employs a high-performance toroidal transformer, a pure focus capacitor of 50 φ x110mm, and four α - capacitors. The total electrostatic energy of 160,000 millijoules provides sufficient current energy supply even during peak hours.
In the power amplifier section, the pre-drive stage and power section, and the left and right channels are separated to improve the stability by 4 power source system.

Equipped with a CD direct connector, transmission can be performed without passing through the input selector.

The phono inputs have a MM position, a Hi-MC position directly connected to the equalizer, and an MC transformer (switching between High and Low).
The MC transformer is a super linear step type equipped with two monaural types using super permalloy cores made by Magnetic Inc. (USA) with excellent magnetic properties.

The equalizer amplifier section uses a Hi-Precision equalizer with a DC amplifier configuration, and has an excellent characteristic of ± 0.2 db over a wide range of 20 hz to 300 khz.
This circuit is also equipped with a diamond differential circuit with excellent high-speed response.

The AWD high-performance type is used for the main small electrolytic capacitor, the copper foil styrene capacitor is used for the small capacity film capacitor, and the RM resistor with excellent sound quality is also used.

It uses a large heavy aluminum block heat sink with excellent heat radiation effect and prevention of modulation distortion due to vibration in the power transistor.

Uses a copper plated chassis that prevents electromagnetic distortion.

Mirror finish is applied to the side wood.

There are 2 color variations of black and silver.

Model Rating

Type	Integrated DC amplifier
<Power Amplifier Section (Twin Diamond Balanced Drive Amp system)>
Effective output (both channel drive)	180W + 180W (6 Ω, 10 Hz to 20 kHz) 160W + 160W (8 Ω, 10 Hz to 20 kHz) 250W + 250W (4 ω, 1 kHz) 210W + 210W (6 ohm, 1 khz) 180W + 180W (8 ω, 1 kHz)
Total harmonic distortion factor	0.003% (8 Ω, 10 Hz to 20 kHz, Effective Output) 0.005% (6 Ω, 10 Hz to 20 kHz, 1/2 Effective Output)
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1)	0.003% (8 Ω, Effective Output)
Output Bandwidth (IHF, both channel operation, THD0.03%)	5 Hz to 80 kHz
Damping factor (new IHF, 20 Hz to 20 kHz)	100 (6 Ω)
Frequency Response (1W)	DC ~ 300 khz + 0 -3dB
Envelope distortion	Below the measurement limit
TIM Strain (Sawtooth method)	Below the measurement limit
Slew rate	± 300 v / μ sec (6 Ω)
Rise time	0.5 μ sec
<Equalizer amplifier section (Hi-precision equalizer)>
Input Sensitivity / Input Impedance (1 kHz)	Phono MM : 2.5mV/47k Ω Phono High MC : 2.5mV/100 Ω Phono MC Low : 100 μ V/3.2 Ω (Uses MC transformer) Phono MC High : 300 μ V/40 Ω (Uses MC transformer) CD, Tuner, Tape1, 2 : 150mV/47k Ω
Phono maximum allowable input (1 kHz, THD 0.01%)	MM:300mV High MC:300mV MC High : 35 mV (Transformer Type)
Output Level / Impedance	Tape rec : 150mV/600 Ω
RIAA Deviation (MM, Rec out)	20 Hz to 300 kHz ± 0.2 dB
Signal-to-noise ratio (A network, short circuit)	Phono MM:90dB Phono MC : 80 dB or more (100 μ V) CD, Tuner, Tape : 110 dB
Tone control	Bass : ± 10 dB (20 Hz) Treble : ± 10 dB (20 kHz)
Tone selector	Bass : 100 Hz, 200 Hz Treble : 4 kHz, 8 kHz
Subsonic filter	16 Hz (-3dB, 6dB/oct.)
Audio Muting	-20dB
<General>
Rated power consumption (Electrical Appliance and Material Control Law)	370W
External dimensions	Width 466x Height 161x Depth 431 mm
Weight	20.5kg