Luxman SQ 503X integrated amplifier

General:

Around 1970 Luxman company came with its first "high quality" integrated amplifier on the European market. This amplifier was a modern design with excelent characteristics. It had a full complementary output stage and a differential input stage of the power amplifier. It is symmetric supplied and the power supply stage was generously built for a 2x20W amp.

Inside the amplifier, top view, new transistors, drivers and output.

Bottom view.

Special futures:

Specifications in txt format

 

Schematic:

Download the schematics in jpg of the SQ503x here.

 

Sound:

The sound of this amp is a pleasure to listen to. 

 

Modifications:

This amp needs to be updated as the transistors and the capacitors are outdated. The transistors of the pre stages are noisy.
Use BC550/560C or equivialent.
The drivers are often defective and the power transistors of the output stage may be obsolete.
I used BD139/140 and 2SA1694 & 2SC4467 of Sanken, works great.

 

© Hans Hilberink - PE1MMK ® 2003 - Last update: 15-02-2010.