Sansui AU-555A

 The AU-555 has long been one of the most attractive control amplifier values in the medium power field. Now-as the improved AU-555A - it's even more of a buy, with more power, more features and more style than ever. Take power, for example. It's up from an ample 60 watts to 33/33 watts at 4 Ω. And now intermodulation distortion as well as total harmonic distortion are limited to under 0,5%. Take performance. The AU-555A offers tone quality very nearly on a par with Sansui's 120 watt top-of-the-line AU-999. in fact, performance generally is quite comparable to that of much larger units despite the AU-555A's compact size. A triple tone control circuit has also been added to achieve new standards in trully accurate sound. In addition, there has been a widening of the power bandwidth to from 20 to 40,000 Hz, and the unit now is housed in a handsome walnut cabinet. Versatility hasn't been neglected, either. The new AU-555A features two speaker switches, independently usable preamplifier and power amplifier sections, five outputs and seven inputs. Add all those assets together and you begin to appreciate what Sansui means by "improved". And what the AU-555A can mean you.

 Semi-Complementary SEPP Circuit

The AU-555A's power amplifier utilizes a semicomplementary SEPP-ITL-OTL Darlington circuit with all silicon power transistors. It delivers music power (IHF) of 85 watts and continuous power of 33 watts per channel at 4 Ω. Total Harmonic Distortion and Intermodulation Distortion are both less than 0,5% and the power bandwidth is a wide 20 to 40,000 Hz.

Low-Noise Preamplifier Section

Carefully selected low noise silicon transistors are employed in the preamplifier section to enable the AU-555A to achieve an unprecedented low noise level.

In performance, that means a greatly expanded dynamic range and increased sound transparency for pianissimo notes.

Negative Feedback Amplifiers

Better frequency response, and better distortion and signal-to-noise characteristics are achieved by using negative feedback amplifiers in all amplifier stages.

 Direct-Coupled Circuitry

The AU-555A employs direct-coupled circuitry wherever possible to get around the problem of poor phase characteristics common to electrolytic capacitors at high frequencies. But where coupling capacitors are necessary, circuit impedance has been raised and mylar capacitors employed or mylar capacitors have been used in parallel for improved response at high frequencies. The human ear can readly detect the difference.

Triple Tone Control Circuit

A T.T.C. system has been added to the AU-555A to achieve the truly accurate reproduction obtained with variable equalizers. This system enables improved compensation for room acoustics and for irregularities in program sources. The bass, midrange and treble circuits can all be controlled in small, significant steps.

Silicon Transistors Throughout

Exceptional high-end frequency response and linearity are obtained by using silicon transistors exclusively.

Separable Preamplifier and Power Amplifier

The preamplifier and power amplifier section of the AU-555A can be utilized separately to from an advanced electronic crossover stereo system. The great performance potential of each of these amplifier sections can by more fully exploited through such usage.

 Ripple Filter Power Supply Circuits

Detrimental hum in high fidelity reproduction has been eliminated in the AU-555A by the use of ripple filter circuits in the power supplies for the preamplifier and power amplifier sections. Completely stabilized power supplies are the result.

Two Phono Input Circuits

The AU-555A incorporates two 50 k Ω phonograph input circuits. This permits the connection of two different cartridges for comparison purposes or to hear different types of music with varying timbre.

Complete Accessory Circuit ystem

The AU-555A's complete range of accessory circuits includes a DIN connector for connecting a tape recorder or deck; high and low filter circuits; loudness control circuit, tape monitor circuit which permits monitoring a tape as it is recorded; headphone jack circuit, and foolproof one-touch type speaker output terminals.

Attractive and professional Styling

Housed in a rich walnut cabinet, the AU-555A has an expensive extrusion front panel and has been carefully color-treated in black to give it the sophisticated appearance that is the hallmark of all Sansui professional components.

Specifications  AU-555A

Power Amplifier  Section

Power Output (at rated distortion)

Music Power (IHF): 

80 watts ±1 dB into 4 Ω at 1,000 Hz; 

60 watts ±1 dB into 8 Ω at 1,000 Hz

Continuous  Power (each  Channel):

33/33 watts  ±1 dB into 4 Ω

25/25 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 40,000 Hz

Load Impedance:  4 Ω to 16 Ω

Frequency Response  (at normal listening level):  20 to 40,000 Hz, ±1 dB

Input Sensitivity:  1V at rated output

Input Impedance:  100 kΩ

Damping Factor:  50 at 8 Ω load

Channel Separation (at rated output 1,000 Hz):  better than 60 dB

Hum and Noise (IHF):  better than 100 dB

Preamplifier Section

Output Voltage [Maximum/Rated]:  5 V / 1 V

Total harmonic Distortion:  less than 0,1% ata rated output voltage

Frequency Response:  20 - 30,000 Hz ±1 dB

Channel Separation (at 1 kHz rated output voltage):

Phono 1 and 2 : better tahn 45 dB

Tuner and Aux : better than 50 dB

Hum and Noise (IHF):

Phono 1 and 2 :  better than 70 dB

Tuner and Aux :  better than 80 dB

Input Sensitivity / Impedance (1,000 Hz for rated output):

Phono 1 and 2 :  2 mV (50 kΩ)

Tape Mon (Pin) :  180 mV (50 kΩ)

Tape Rec (DIN) :  180 mV (50 kΩ)

Aux :  180 mV(50 kΩ)

Recording Output (at 1 kHz rated input voltage): 

Tape Rac (Pin) :  180 mV

Tape Recorder (DIN) :  30 mV

Equalizer:

Phono :  RIAA NF Type

Mic :  flat NF Type

Controls

Bass:  +12 dB -12 dB at 30 Hz

Midrange:  +5 dB -5 dB at 1,500 Hz

Treble:  +10 dB -10 dB at 15,000 Hz

Loudness:  +8 dB at 50 Hz; +3 dB at 10 kHz

Filters

Low:  -8 dB at 50 Hz

High:  -7 dB at 10,000 Hz

General

Switches:

Mode:  Stereo / Mono

Tape Monitor:  Source / Playback

Selector:  Phono-1 / Phono-2 / Tuner / Aux

Speaker Switch 1 and 2:  On / Off

Semiconductors:  23 Transistors; 2 Diodes

Power Requirements:  100, 117, 220, 240 V  50/60 Hz

Power Consumption:  130 watts Max.

Dimensions (H x W x D):  135 x 395 x 278 mm (5⅜ " x 15⅜ x 10⅞") excluding rubber stand and knob

Weight:   8 kg  (17,6 lbs) net