Audio Database

AU - α 707 xr
Commentary

Pre-main amplifier equipped with newly developed Hyper α -X balance circuit.

In order to eliminate distortion caused by element asymmetry, we have developed and adopted a Hyper α -X balanced circuit based on our original X balanced amplifier technology.
In addition to the conventional balance circuit, this circuit has newly introduced a high CMRR type constant current circuit at the first stage of the power amplifier and pre-amplifier, which determine the dynamic characteristics of the amplifier. This circuit achieves a theoretical CMRR improvement of 140 dB. This reduces current variations due to DC offset caused by element asymmetry and reduces dynamic noise generated in the circuit.
In addition, all stages are balanced so that music signals can be transmitted and amplified simultaneously, and the amplification circuit and ground circuit are completely separated to eliminate adverse effects caused by back electromotive currents and external noise from speakers.
In addition, dedicated amplifiers are placed on the + side and - side of the output respectively, and a push-pull system is adopted in which a total of four amplifiers drive the speakers under the same conditions.

The power stage is equipped with an audio-only device, NM-LAPT, which has excellent high-frequency characteristics and current limit value.

DC amplifier configuration is used for all stages from input to output.
In addition, the performance of the DC amplifier is improved by adopting the NEW diamond differential circuit which can take out the output of the - side without phase inversion, and by improving the response to the instantaneous signal and suppressing the generation of TIM distortion.
In addition, in order to make the circuit wide range and high speed, the first stage FET is cascade-connected to eliminate the sound quality degradation that occurs when connecting to external devices with different impedances.

In order to prevent unbalanced power supply, a closed loop configuration is adopted in which the power supply is separated from the ground. The power stage and voltage amplification stage are completely separated. This provides a stable large current and protects the signal from the natural vibration of the power supply and noise generated during charge and discharge.

Reinforced twin monaural construction is used to prevent vibration from the power and signal systems.
First, large transformers and electrolytic capacitors are installed in the center, and the power unit, which consists of power transistors, radiators and other signal systems, is placed symmetrically to ensure an optimal weight balance.
In addition, we have introduced a unique technology called Integrated Mechanical Feedback, and we use pure copper, Teflon sheet, and Teflon tape for routes where vibration is transmitted, such as between the master volume and chassis, between the transformer and chassis, and between the NM-LAPT and radiator, to effectively suppress vibration.
In addition, an elliptical insulator with a special structure blocks external vibration.

It is equipped with a power amp direct input that can directly input the digital source music signal to the power amp section, and a balance input terminal.

A 6-row detent volume is used.

Equipped with source power direct, REC selector, AC outlet, etc.

Model Rating
Type Integrated amplifier
Power Amplifier Unit
Effective output (10 Hz to 20 kHz
Simultaneous operation of both channels)
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 0.003% or Less (8 Ω)
Damping factor 150 (8 Ω)
Frequency Response (1W) DC ~ 300 khz + 0 -3dB
Input Sensitivity / Impedance 1V/5k Ω (1 kHz)
Signal-to-noise ratio (A network) 120 dB or more
Dynamic Power 405W (2 Ω)
320W (4 Ω)
210W (6 Ω)
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, Tape/DAT1, 2 : 150mV/20k Ω
Phono maximum allowable input MM(THD 0.01%):210mV
MC(THD 0.1%):21mV
Frequency Response (1W) Phono MM : 20 Hz to 20 kHz ± 0.2 dB
CD, Tuner, Line, Tape/DAT1, 2 : DC ~ 200 khz + 0 -3dB
Signal-to-noise ratio (A network) Phono MM : 88 dB or more
Phono MC : 70 dB or more
CD, Tuner, Line, Tape/DAT1, 2 : 110 dB or more
Tone control Maximum variation of Bass : ± 6 dB (50 Hz)
Maximum variation of Treble : ± 6 dB (15 kHz)
Subsonic filter 16 Hz (-3dB), 6dB/oct.
Loudness +6dB(50Hz)
+4dB(10kHz)
<General>
Rated power consumption 330W
External dimensions Width 466x Height 162x Depth 452 mm
Weight 23.0kg