SANSUI AU-D707X Decade

Commentary

This is an integrated amplifier based on the AU-D707X. The power supply has been reinforced to improve the reproduction capability in the low frequency range.

The basic configuration of the amplifier is a twin diamond X balanced amplifier.
In the conventional amplifier, the current to the speaker is sent from the positive side and the negative side is simply connected to the ground. Therefore, when the back electromotive force flows into the ground on the negative side, IHM distortion occurs due to mutual interference with the ripple current of the current. In addition, NFB for reducing the distortion is only on the positive side, and the negative side is not controlled at all.
The Twin Diamond X balanced amplifier has a balanced configuration for all signal circuits from input to output, power supply circuits, and NFB circuits. By driving the speakers equally from both + and - sides, the influence of ground is eliminated.
In addition, in order to make the power transistor work more effectively, the speaker drive capability has been improved by adopting a two stage configuration in which the power transistor is driven by current using a twin diamond differential circuit.

In order to obtain a stable speaker drive even during peak hours, the power supply section is equipped with a 40,000 μ F total condenser composed of a pure focus condenser and an HS condenser with excellent transient charge-discharge characteristics, and a super-heavyweight power transformer.
In addition, the L/Rch of the pre-part, pre-drive part and power part is composed of 4 independent power sources, and noise generated from the power source is suppressed by combining with a balanced power source system without earth.

In order to take advantage of the performance of the MC cartridge, it is equipped with an MC transformer using a permalloy core with high purity and low magnetostriction. The transformer unit is fixed with a filler to prevent vibration and strain.
By making the load impedance of the MM/MC cartridge completely independent, the optimum load can be selected, and optimum matching and ideal amplification which were impossible with conventional built-in MC transformer and external transformer are realized.

It is equipped with side wood, and the resonance mode is suppressed out of band by the combination of metal and wood.

Equipped with a 2-step switching type tone selector.

Equipped with a subsonic filter.

Gold plated terminals are used for Phono input and CD input.

The Phono input has four positions : MM, High MC, and MC transformer (High and Low).

The equalizer section uses a Hi-Precision equalizer with a discrete DC amplifier configuration.

Equipped with Rec selector.

Model Rating

Type	Integrated DC amplifier
Power Amplifier Unit
Effective output (10 Hz to 20 kHz, both channels driven)	160W + 160W (6 Ω) 130W + 130W (8 Ω)
Total harmonic distortion rate (10 Hz to 20 kHz)	0.003% (8 Ω, Effective Output) 0.005% (6 Ω, at 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
Slew rate	± 200 v / μ sec (6 Ω)
Rise time	0.5 μ sec
Equalizer Amplifier Section
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/5.3 Ω (Uses MC transformer) Phono MC High : 250 μ V/40 Ω (Uses MC transformer) CD, Tuner, Tape1, 2/PCM : 150mV/47k Ω
Phono maximum allowable input (1 kHz, THD 0.01%)	MM:300mV High MC:300mV MC High : 25 mV (Transformer Type)
Signal-to-noise ratio (A network, short circuit)	Phono MM:90dB Phono MC:80dB CD, Tuner, Tape : 110 dB
Tone selector	Bass : 100 Hz, 200 Hz Treble : 4 kHz, 8 kHz
Subsonic filter	16 Hz (-3dB, 6dB/oct.)
<General>
Rated power consumption (Electrical Appliance and Material Control Law)	320W
External dimensions	Width 466x Height 161x Depth 431 mm
Weight	21.5kg