General:

 Small amplifier with moderate power capability.

 

Specifications:

 

Special futures:

This little GEM is a real nice amp, well built, cheap at the time it was issued, very nice sound and good parts used by Rotel.

Some amps had the REC logo and others the Rotel name on the front.^

 

User Manual:

not available.

Interior: the updated power amp ^

 

Schematic:

Click here to download the Rotel RA-210 service manual in PDF format

 

Interior ^

 

Modifications:

Some capacitors should be checked and the power supply rail should be updated to modern standards.

The original power transistors, Matsushita 2SD317 - TO220 package, will break down after many cold/warm cycles, so heatsinking is crucial. Also the drivers 2SC828 & complementary 2SA564 are a little under-dimensioned, so heatsinking is important here too, otherwise breakdown is inevitable. You may replace these transistors by more rugged ones, I used Hitachi 2SD476 as final power transistors, these work fine and do not break. Some small changes to the original electronic design can do well to the stability and sound of the amplifier, at some places there has been seriously saved on parts-cost by underdimensioning or omitting some crucial parts in the original design. Potentionally this amp can be a well sounding HiFi amplifier delivering +10 Watts RMS per channel output power.

On the photos you can see how I did the update. If you are in Europe set the mains voltage to 240 V:

After the upgrade my amp had 2 x 12 Watts RMS power output.
The most significant limitation of this amp is the relatively small under-dimensioned power transformer.

The open amp ^

Adjusting the amp ^ The idling current and the DC-offset of the power amp section should be checked and readjusted.

 

The RIAA amp section: a traditional 2 transistor setup. ^

 

Final update interior ^
 

Original back panel ^

Updated back panel ^

 

Sound:

Exceptional for such a small footprint and low powered amplifier.