Sansui AU-555A integrated amplifier

General: 

This amplifier produced in the early 1970’s by Sansui Company inc. Japan .

 

Photos:

front ^

Front detail.

detail back.

Bottom view: legendary Hitachi 2SC1030 power transistors ^

Original interior view with main pcb ^

The restored power supply.
 

Unrestored pcb of the power amp and the heatsinked driver transistors.
 

The restored pcb of the power amp, the capacitors of the output are left as is, as they are ok for now, all other caps are replaced.

 

Special futures:

This amp was well known by audio enthousiasts as it has the mid-range tone control, very typical for this amplifier model range of Sansui.
All High quality amps of Sansui made in that time frame are equipped with mid-range tone control.

 

Schematic:

Click here to see the main schematic diagram in jpg format

Click here for the user manual of the Sansui AU555A in PDF format

 

Hitachi 2SC1030 power transistors ^

 

Modifications:

Most electrolytic capacitors can be replaced. The driver transistors can get quite noisy, they should be heat sinked and/or can be replaced by
modern drivers. The power amp input transistor can be replaced by a modern input transistor when it starts producing noise,
a 2SA1015 or a BC560C do the job ok.
The diodes of the power supply should be replaced by modern >100V 10A diodes. Coupling capacitors in the signal path should be replaced.
There are some electronic design flaws in this amplifier but:
If you are aquainted with electronics and amplifier design and amplifier building principles, you will be able to make this to a
very good HiFi amplifier with outstanding specs and very good sound, outperforming many competitor amps.
This amplifier is worth updating: (There are many tricks that the electronics expert knows to get the most out of an AU555A).

Here a power supply Elna capacitor that is ok after so many years, it has 2260 uF, no need to replace.

 

Sound:

These Sansui series of audio components soon got legendary by their outstanding build quality and extra features and good sound.

© Hans Hilberink - PE1MMK ® - 2003, Last update: 25-01-2019.