SANSUI AU-D907

Commentary

A DC pre-main amplifier equipped with Sansui's original diamond actuation circuit to improve dynamic distortion for live music playback.

The equalizer, flat amplifier / tone control and power amplifier are all configured as push-pull output DC amplifiers with improved bare characteristics.
In addition, in pursuit of sound quality, input capacitors for all block stages are eliminated, and a direct-coupled system with FET inputs for all stages is adopted to achieve pure music signal transmission and a wide range.
All the FETs used are selected to have low-noise and high-gm characteristics. In addition, each block stage has a symmetrical circuit structure with symmetry, which greatly reduces harmful TIM distortion and envelope distortion and improves sound quality.

The power amplifier section is a drive circuit with a power stage and 3-step amplification configuration.
The first stage is an operation circuit with constant current using dual FET that allows large current to flow with low noise, the second pre-drive stage is a diamond operation circuit (PAT. PEND) with dual complimentary service that suppresses the generation of TIM distortion with powerful drive capability, and the third stage is a current operation push-pull circuit.
The final power stage uses Sansui Custom NM (Non Magnetic) transistors, and the entire circuit is composed of symmetrical symmetrical circuits.

The MC head amplifier is a target circuit using SANSUI's original push-pull input / output circuit. It is a direct coupled system.
The first stage uses a newly developed low-noise, high-gm P-channel and N-channel multiple para-connected new-type FET. The independent power supply for the left and right channels realizes stable operation from minute input to large transient input.
In addition, the target circuit configuration greatly improves the dynamic characteristics.

The equalizer amplifier is a direct-coupled amplifier without the input capacitor, which affects the sound quality, and is equipped with a diamond drive circuit.
The first stage is equipped with low-noise, high-gm, dual-FET operation input circuit, cascode bootstrap + constant current circuit, the second and third stages are equipped with diamond operation circuit + current operation push-pull circuit, and the output stage is equipped with SEPP circuit with Darlington connection to realize sufficient current margin and low output impedance.
In addition, the target circuit configuration significantly improves dynamic distortion.

The flat / tone amplifier is also a direct-coupled DC amplifier configuration.
The first stage is an operation circuit with cascode connection and current source using dual FET of low noise and high gm, and the second stage is a current operation push-pull circuit with current mirror.
Similar to the DC power amplifier section, it has an excellent configuration of open loop characteristics to reduce TIM distortion.
You can also use the jump switch to jump directly from the equalizer amplifier to the power section.

The power supply to the power amplifier section uses a high-regulation large toroidal transformer with two windings and two rectifier circuits with independent left and right channels of the power stage.
The pre-drive stage uses an EI transformer with two independent power supply systems for left and right channels, for a total of four power supply systems.
The MC head amplifier section and the DC flat amplifier section are independently supplied by a stabilizing power supply.

Direct speaker output jacks. Two types of speaker systems can be connected : OFF, A, B, or A + B.
Especially, the A system is connected directly to the DC power amplifier stage with the shortest distance without passing through the changeover switch.

Features include a subsonic filter (16 hz, -3dB, 6dB/oct), audio muting (-20dB), tone jump switch, balance control, two circuit tape play / copy function, and input selector with indicator.

The Phono input terminal is gold-plated.

By separating the pre-main, the pre-amplifier section and the power amplifier section can be used independently.

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

Ground terminal.

Model Rating

Type	Wide-range DC pre-main amplifier
Power Amplifier Unit
Effective power	100W + 100W (10 Hz ~ 20 kHz, THD 0.008%, 8 Ω) 100W + 100W (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)	95 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) : 0.005% 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 : 75 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.)
Headphone jack output	120 mW (8 Ω)
<General>
Load impedance	4 ~ 16 Ω
Rated power consumption (Electrical Appliance and Material Control Law)	250W
External dimensions	Width 430x Height 168x Depth 428 mm With Rack-Mount Adapter : Width 482x Depth 455 mm
Weight	20.8kg With rack-mount adapter : 21.2 kg
Sold Separately	Rack-Mount Adapter BX-7 (1 pair, ¥ 3,000)