What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Sansui AU-555

 Solid State Control Amplifier
In introducing the Au-555, Sansui sets still another "first" in its long list of audio innovations: the first time a truly professional control amplifier of Sansui quality has been available in the medium power price range.
The AU-555 incorporates many of the features of Sansui's larger AU series amplifiers, including an all silicon solid state design, professional arrangement of controls and an black control panel. At the same time, it offers several distinctive features of its own. In performance, a total music power output of 60 watts, a power bandwith from 20 to 30,000 Hz, and a distortion factor of only 0,5% are made possible by utilizing special SEPP-ITL-OTL circuitry. Pre- and main amplifier sections designedfor independent usage, two adjustable speaker damping factors, a 4-position speaker selector switch, and four outputs and seven inputs give it almost unlimited versatility. These are only a few of the many features offered by the new AU-555 - features that make it the first uncompromised control amplifier in the medium power range.

 All Silicon Solid-State Design
Silicon transistors in all stages of the amplifier assure lower distortion and a higher signal-to-noise ratio even at low power levels. They also provide greater stability against high temperatures. This results in a greater dynamic range for the highest standards of sound reproduction with excellent linearity.

Most Advanced Circuitry
The transformerless arrangement (SEPP-ITL-OTL) of a complementary Darlington circuit and the use of epitaxial silicon power transistors provide the music power of 60 watts, continous power of 25/25 watts with less than 0,5% harmonic distortion and a power bandwith of 20 to 30,000 Hz.

NF-Type Bass and Treble Control
Expensive NF-type tone controls incorporate low-noise silicon transistors for minimum distortion (only 0,1%) These controls consist of two separate knobs each, one for each channel, for more minute adjustment.

Matchless Appearance
The extruded front panel, satin-black face, and professional control arrangement are inherent family features of Sansui's entire AU control amplifier series.

All-Printed Circuit
Printed circuits in all stages of the amplifier greatly improve the channel separation, stability and reliability of the AU-555.

Newly-Developed Power Transformer
A new power transformer, designed and manufactured especially for transistors at Sansui's own factory, assures better power regulation without hum from the source.

Damping Factor Selector Switch
A 2-position damping factor selector switch (High 45 and Low 12) allows matching the AU-555's damping factor with the characteristics of any speaker system.

 Negative Feedback Amplifier
Negative feedback amplifiers are used in all stages from the first to the final for appreciable improvements in frequency response, signal-to-noise ratio and distortion. The main amplifier has a frequency response of 20 to 100,000 Hz +/-1 dB. The preamplifie output has a distortion factor of less than 0,1% at the rated output voltage of 1 volt.

Double Protection for Power Transistors
Sansui's exclusive electronic protective devices prevent damage to the power transistors if an accidental short should occur. in addition, the AU-555 is equipped with quick-acting fuses, which protect the power transistors in case of overloads.

Independent Pre- and Main Amplifiers
Both pre-and main amplifier sections are designed to be used independantly for more versatility.

Four Outputs and Seven Inputs
Yhe AU-555 is provided with all the outputs and inputs of the largest amplifiers: preamp, tape rec., and two speaker outputs, two phono,tape head,microphone and three other inputs

Two Phono Inputs
The AU-555 is provided with two Phono inputs. phono 1 and 2 have the input impedance of 47 kohms and 100 kohmsrespectively. Either can be used depending on preference. Generally a crtridge connected to the 47 kohms input produces a soft and mild tone. Connected to the 100 kohms input, it delivers tones with accented high frequencies.

 Specifications  AU-555
Audio Section
Power Output (at rated distortion)
Music Power (IHF): 
60 watts ±1 dB into 4 Ω at 1,000 Hz; 
50 watts ±1 dB into 8 Ω at 1,000 Hz
Continuous  Power (each  Channel):
25/25 watts  ±1 dB into 4 Ω
20/20 watts  ±1 dB into 8 Ω
Total Harmonic Distortion:  less than 0,5% at rated power output
Intermodulation Distortion (60 Hz : 7,000 Hz = 4:1 SMPTE method):  less than 0,8%
Power bandwidth (IHF):  20 to 30,000 Hz at 8 Ω (0,5% distortion)
Load Impedance:  4 Ω to 16 Ω
Frequency Response  (at normal listening level):  20 to 80,000 Hz, ±1 dB
Input Sensitivity:  1V at rated output
Input Impedance:  100 kΩ
Damping Factor:  12 and 45 at 8 Ω load
Channel Separation (at rated output 1,000 Hz):  better than 50 dB
Hum and Noise (IHF):  better than 100 dB
Input Sensitivity / Impedance (1,000 Hz for rated output):
Phono 1:  2 mV/ 47 kΩ
Phono 2:  2 mV/100 kΩ
Tape head:  1,5 mV/200 kΩ
Aux 1:  200 mV/100 kΩ
Aux 2:  140 mV/100 kΩ
Microphone:  3,5 mV/ 10 kΩ
Tape monitor:  150 mV/ 100 kΩ
Recording Output (at rated input):  140 mV
Bass: +16 dB -16 dB at 20 Hz
Treble:  +13 dB -13 dB at 20 kHz
Loudness:  8 dB at 50 Hz; 2,5 dB at 10 kHz
Low:  -12 dB at 20 Hz
High:  -10 dB at 20,000 Hz
Muting (audio):  0 dB,  -20 dB
Semiconductors:  22 Transistors; 6 Diodes; 4 Thermistor; 1 S.C.R.
Power Requirements:  100, 117, 220, 240 V  50/60 Hz
Power Consumption:  120 watts Max.
Dimensions (W x H x D):  382 x 111 x 267 mm 
(15" x 4 x 10") excluding rubber stand and knob
Weight:   7,9 kg  (17,4 lbs) net

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