Audio Database

SU-A70
Commentary

Concise G integrated amplifier with single component G series technology.

The power amplifier section uses MOSclassAA circuit, an original circuit technology.
This circuit employs a pure class A voltage-controlled amplifier using a power MOS-FET as an amplifying element and a class B operating current supply amplifier composed of bipolar transistors. Voltage amplification and current supply to speakers are handled by separate amplifiers.
This combines the advantages of both MOS-FET and bipolar transistor.

An R core transformer is used for the power supply.
The R-core transformer has a circular cross section, whereas the general transformer has a square cross section. Therefore, the coil can be tightly wound to form a uniform magnetic flux, which results in very little magnetic flux leakage.

Virtual battery operation is adopted for the power supply circuit.
100 VAC power supplies for home use contain various types of noise. In conventional power supply circuits, this noise enters the audio circuit through the reference potential generation circuit and pollutes the music signal.
The Virtual Battery Operation takes advantage of the characteristics of the FET element and protects the audio signal and improve sound quality by skillfully blocking the noise from the AC power supply.

Audio-only parts are used, and the parts are selected as a result of extensive listening tests.
In particular, we have adopted the Master Series electrolytic capacitor for the power supply. Although the basic concept of this capacitor is vibration control structure, more than 20 types of capacitors with different components such as aluminum foil, electrolyte foil, electrolyte, separator, etc., and sound quality was thoroughly examined before adoption.

The case is made of 2.5 mm thick aluminum, and the front panel is made of 7 mm thick aluminum front panel.
This realizes a housing with superior vibration damping and magnetic properties.

The volume uses a gold-plated brush and high-sound quality carbon resistor.

Speaker terminal for banana plug is adopted.

Comes with a system remote control for direct control of the CD player, tuner and cassette deck.

Model Rating
Type Pre-main amplifier
Rated Output (20 Hz to 20 kHz, 0.05%) 40W + 40W (6 Ω)
33W + 33W (8 Ω)
Maximum practical power 60W + 60W (EIAJ, 4 Ω)
Rated distortion factor 0.05% (20 Hz to 20 kHz, Rated Output, 8 Ω)
Damping factor 60 (8 Ω)
Load impedance 4 ~ 16 Ω
Line input frequency characteristic Tuner, CD, Aux, Tape1/2 : 20 Hz to 20 kHz + 0 -0.3 dB
3 Hz ~ 80 kHz + 0 -3dB
Equalizer deviation 30 Hz to 15 kHz ± 1 dB
Input Sensitivity / Impedance Tuner, CD, Aux, Tape1/2 : 150mV/22k Ω
Phono MM : 2.5mV/47k Ω
Phono maximum allowable input MM:150mV(0.01%)
Signal-to-noise ratio Tuner, CD, Aux, Tape1/2 : 83 dB (EIAJ)
99dB(IHF'66)
Phono MM:78dB(EIAJ)
78dB(IHF'66)
Tone control characteristics Bass : ± 10 dB (50 Hz)
Treble : ± 10 dB (20 kHz)
Rated output voltage Tape1/2 rec out:150mV
Pwer 100 VAC, 50Hz/60Hz
Power consumption 110W
External dimensions Width 270x Height 113.5x Depth 339.5 mm
Weight 5.7kg
Attachment Wireless Remote Control