SANSUI AU-7700

Commentary

This pre-main amplifier was completed by making full use of experience and technology in high-grade components.

The rear panel structure consists of a phono circuit and input terminals that face upward and are connected directly to the equalizer amplifier board at the shortest distance.
This eliminates the need to use shielding wires, which cause degradation of high-frequency characteristics, and realizes a high SN ratio and good sound quality with high-frequency characteristics.

The printed circuit board of the control amplifier, rotary switches, lever switches, and various volumes are directly attached to the integrated structure.
This prevents failures such as poor connection and improves reliability.

With the chassisless structure, one point grounding is implemented to suppress current mutual interference.

The power amplifier consists of a 3-stage Darlington drive stage with a differential amplifier circuit at the first stage and a parallel push-pull type power stage.
The parallel push-pull system combines four power transistors with the same characteristics per channel, and the linearity of current characteristics is good. The pure complimentary service circuit directly connected to all stages has excellent phase characteristics, large negative feedback is applied over a wide band, and flat frequency characteristics are obtained.

The equalizer circuit is a 4-chip configuration with a differential amplifier at the first stage input.
By using carefully selected elements, an excellent dynamic range is achieved.

Equipped with triple tone control that can adjust Bass, Treble, and Midrange.
The tone amplifier has a 6-chip configuration with a differential amplifier circuit at the first stage. Low-noise type transistors and high-precision CR elements are carefully selected and used. In addition, a detent type volume with less error is adopted.

It is equipped with a tone selector switch that allows you to select the Bass and Treble of the tone control to the falling and rising frequency of 3 points.

It adopts a high filter that adopts an active filter exclusively for NF type with good characteristics.
Two types of attenuation characteristics can be selected. In the defeat position, the attenuation characteristic is independent of the filter circuit and becomes flat.
Also equipped with a 2-stage switching low filter.

Since the potential of the input / output circuit of each block stage is approximately 0 V, click noise generated when the selector switch is switched is prevented.

In the case of defeat, a complete defeat system is adopted, which bypasses the tone circuit and filter circuit.
In this defeat, ± 2 power supply operation is performed for all stages.

The power supply section is equipped with a heavy-duty power transformer and 10,000 μ Fx2 large-capacity power supply to provide ± 2 power supply with good regulation and resistance to load fluctuations such as Dainyu Chikara.
The equalizer circuit and tone circuit are supplied with power by a ± 2 power supply stabilization circuit with windings of a different system from the power stage to suppress the influence of the power stage.

An electronic circuit is combined with a high-sensitivity relay, and a protective circuit using a short-cut fuse is adopted.
This circuit consists of four sensing circuits : a temperature sensing circuit for power transistors, a transistor safety area sensing (ASO) circuit, an overcurrent sensing circuit, and an abnormal voltage sensing circuit for speaker protection.

Equipped with a 2-stage switching loudness switch that can be switched between the normal low-high-band boost and the low-band booth only.

You can also fine-tune the music level with -15dB and -30dB attenuation.

Equipped with a stereo normal / reverse / monaural mode selector switch.

Equipped with two tape monitor circuits, it can record program source and monitor during recording.
Tape copies are also available.

It is equipped with a pre-main disconnect switch and can be used independently by disconnecting the preamplifier and main amplifier.

In the Phono input circuit, the load impedance of Phono1 can be switched to three levels of 30k Ω, 50k Ω and 100k Ω depending on the cartridge.

Two sets of speaker systems, A and B, can be operated independently or simultaneously by switching the switch.

Equipped with large grounding terminal and spare AC outlet.

Uses die-cast side panels.

It uses a metal knob made of pure aluminum that feels good.

Model Rating

Type	Pre-main amplifier
Effective power	Both channel operation 20 Hz to 20 kHz : 52W + 52W (8 Ω) 1 kHz : 55W + 55W (8 Ω) Single channel operation 1 kHz : 58W/58W (8 Ω)
Music power	250W (4 Ω, 1 kHz)
Total harmonic distortion factor	Pre Amp : 0.1% or less Main Amp : 0.1% or less Over All : 0.1% or less
Cross modulation distortion factor (70 Hz : 7 kHz = 4 : 1, SMPTE)	Pre Amp : 0.1% or less Main Amp : 0.1% or less Over All : 0.15% or less
Power Band With (IHF)	5 Hz to 40 kHz
Frequency response (at 1W output)	10 Hz ~ 50 kHz + 0.5 -1dB
RIAA deviation (30 Hz to 15 kHz)	± 0.5 dB
Damping factor	30 (8 Ω)
Input Sensitivity / Impedance	Phono1 : 2.5mV/30k Ω, 50k Ω, 100k Ω Phono2 : 2.5mV/50k Ω Tuner, AUX, Tape Monitor (Pin/Din) : 100mV/50k Ω Main Amp : 800mV/50k Ω
Phono maximum allowable input (THD <0.2%)	300mV
Output Voltage (1 kHz)	Tape Rec(Pin/Din):100mV/30mV Pre Amp:800mV
Channel Separation (1 kHz)	Phono : 50 dB or more Tuner/AUX, Tape Monitor : 55 dB or higher Main Amp : 60 dB or higher
Hum and noise (IHF)	Phono : 75 dB or more Tuner, AUX : 85 dB or higher Main Amp : 100 dB or higher
Tone control	Bass : ± 13 dB (50 Hz) Midrange : ± 5 dB (1 kHz) Treble : ± 13 dB (15 kHz)
Tone selector	Bass:150Hz/300Hz/600Hz Treble:2kHz/4kHz/8kHz
Loudness (at Volume -30dB)	High & Low : + 10 dB at 50 Hz, + 8 dB at 10 kHz Low:+10dB(50Hz)
Low filter	20Hz=-3dB(12dB/oct) 60Hz=-3dB(12dB/oct)
High filter	7kHz=-3dB(6dB/oct) 12kHz=-3dB(12dB/oct)
Muting	-15dB, -30dB
Rated power consumption	120W
External dimensions	Width 434x Height 130x Depth 315 mm
Weight	12.3kg