SANSUI AU-D707

Commentary

A DC pre-main amplifier with a 3 DC amplifier configuration with a diamond actuation circuit mounted on the equalizer section.

The equalizer, flat amplifier / tone amplifier, and power amplifier are all DC amplifiers. The direct coupling method is adopted in which input capacitors of all stages are eliminated.
The straight DC amplifier configuration provides pure music signal transmission and a wide range.
The inputs of all block stages are FET inputs with low-noise, high-gm characteristics and a full push-pull input circuit.
In addition, each block stage greatly reduces the harmful dynamic distortion in the target circuit configuration.

The power amplifier section follows the circuit configuration of the AU-D907.
In other words, the first stage is equipped with a constant-current operation circuit using dual FET that has excellent low-noise characteristics and allows large current to flow, and the second stage is equipped with a diamond complimentary service circuit using dual differential with improved dynamic characteristics to enhance the drive capability of the pre-drive stage.
In addition, SANSUI Custom NM (Non Magnetic) transistor with excellent linearity is used for the power stage, and it has a symmetrical circuit structure with good dynamic characteristics and excellent sound quality.

The MC head amplifier is a fully symmetrical push-pull configuration with stable performance even for transient input.
The first stage uses low-noise transistors with carefully selected P-channel and N-channel combinations, and the unique symmetrical symmetrical circuit configuration realizes improved dynamic characteristics.

The equalizer amplifier uses a direct-coupled method without input capacitors, which interfere with sound quality, and is equipped with a diamond differential circuit.
The first stage consists of low noise, high gm, differential input with dual FET, cascode bootstrap and constant current circuit, the second stage consists of a diamond differential circuit and current differential push-pull, and the output stage consists of a SEPP circuit with Darlington connection.

The flat / tone amplifier is a direct-coupled DC amplifier configuration without input capacitors.
The first stage is a differential circuit with a cascode connection and constant current using a dual FET of low noise and high gm, the second stage is a current differential push-pull circuit with a current mirror, and the output stage is a SEPP configuration with a two stage Darlington connection to reduce TIM distortion.
In addition, the tone control circuit is a CR type with good variable characteristics, and combined with the tone selector, simple characteristics can be obtained.
When the jump switch is used, the signal jumps through the flat amplifier and directly enters the power section.

An EI transformer is used for the power supply.
The power amplifier section is supplied with two dedicated windings and two rectifier circuits in which the left and right channels are completely independent. Large-capacity electrolytic capacitors (15,000 μ Fx4) and metalized capacitors are used.
In addition, a constant voltage circuit with a separate dedicated winding is adopted for the preamplifier section to suppress the occurrence of TIM distortion and envelope distortion, while taking into consideration factors that lead to improved sound quality such as improved resolution.

The speaker system can be connected in two ways : OFF, A, B, and A + B. When used in the A system, it can be connected directly to the DC power amplifier stage at the shortest distance without passing through the speaker selector switch, and high quality sound can be obtained.

Equipped with subsonic filter (16 hz, -3dB, 6dB/oct), loudness switch, tone jump switch, balance control, and 2-circuit tape play / copy function.

Three spare AC outlets (100W for one interlocked circuit, 250W for two non-interlocked circuits)

Ground terminal mounted

Pre and power can be separated.

Model Rating

Type	Wide-range DC pre-main amplifier
Power Amplifier Unit
Effective power	90W + 90W (10 Hz to 20 kHz, THD 0.008%, 8 Ω) 90W + 90W (1 kHz, THD 0.003%, 8 Ω
Total harmonic distortion factor	0.008% or Less (10 Hz to 20 kHz, 8 Ω at Effective Output)
Intermodulation distortion factor (70 hz : 7 khz = 4 : 1)	Not more than 0.008%
Output bandwidth	3 Hz ~ 70 kHz (IHF, double-channel operation, 1 kHz, 8 Ω)
Damping factor	100 (IHF, Double-channel Operation, 1 kHz, 8 Ω)
Frequency characteristic	DC ~ 500 kHz, + 0 -3dB
Input Sensitivity / Impedance (1 kHz)	1V/47k Ω
Signal-to-noise ratio	125 dB or more (IHF, A-network, short circuit)
Channel Separation (IHF, 1 kHz)	90 dB or more
Rise time	0.5 μ sec
Slew rate	± 200 V / μ sec
Preamplifier Section
Input Sensitivity / Impedance (1 kHz)	Phono-1MM : 2.5mV/47k Ω Phono-1MC : 0.1mV/100 Ω Phono-2MM : 2.5mV/47k Ω AUX, Tuner, Tape Play 1, 2 (PIN) : 150mV/47k Ω
MC compatible impedance	100 Ω or less
Phono maximum allowable input (1 kHz)	Phono MM:350mV(THD 0.01%) Phono MC:30mV(THD 0.03%)
Output Voltage (1 kHz)	Tape Rec1, 2 (at PIN, 47k Ω) : 150 mv Pre Out (at 47k Ω) : 1 V Max Pre Out (at THD 0.05%, 47k Ω) : 4 v
Output Impedance (1 kHz)	Tape Rec1, 2 : 600 Ω or less
Total harmonic distortion factor	Phono MC (1 kHz, 6 V) : 0.01% or less Phono MM (20 Hz to 20 kHz, 6 V) : 0.005% or less AUX, Tuner, Tape Play 1, 2 (20 Hz to 20 kHz, 1 V) : 0.005% or less
Intermodulation distortion factor (70 hz : 7 khz = 4 : 1)	AUX, Tuner, Tape Play 1, 2 (1 v) : not more than 0.005%
Frequency characteristic	RIAA deviation (Phono 1, 2, 20 Hz-20 kHz) + / - 0.2 dB AUX, Tuner, Tape Play 1, 2 : 5 hz to 100 khz, + 0 -1dB
Signal-to-noise ratio (IHF, A-network Short circuit)	Phono MC (input conversion) : -154dBV Phono MM : 90 dB or more AUX, Tuner, Tape Play 1, 2 : 100 dB or more
Channel Separation (IHF, 1 kHz)	Phono MC : 70 dB or more Phono MM : 70 dB or more AUX, Tuner, Tape Play 1, 2 : 80 dB or more
Input-to-input separation (input short, 1 kHz)	Tuner ⇔ Phono MM : 90 dB or higher Tape Play 1, 2 ⇔ Phono MM : 90 dB or more Tuner ⇔ Tape Play 1, 2 : 90 dB or higher Tape Play 1 ⇔ Tape Play 2 : 100 dB or more
Tone control	Bass : ± 6 dB (50 Hz) Tone selector (turnover frequency) : 300 Hz, 150 Hz Treble : ± 6 dB (15 kHz) Tone Selector (Turnover Frequency) : 6 khz, 3 khz
Subsonic filter	16 Hz (-3dB, 6dB/oct.)
Loudness (at volume -30dB)	+10dB(50Hz) +4dB(10kHz)
Headphone jack output	120 mW (8 Ω)
<General>
Load impedance	4 ~ 16 Ω
Rated power consumption (Electrical Appliance and Material Control Law)	230W
External dimensions	Width 430x Height 168x Depth 428 mm With Rack-Mount Adapter : Width 482x Depth 455 mm
Weight	20.1kg With rack-mount adapter : 20.6 kg
Sold Separately	Rack-Mount Adapter BX-7 (1 pair, ¥ 3,000)