Pioneer SA-420 Amplifier

General:

Pioneer Japan introduced this amplifier around 1990.

Special futures:

This amplifier consists of only a RIAA and a power amp section,
tone control is done the same way as in the Luxman L200 series:
in the feedback circuit of the power amp.
The amplifier setup is quite similar to the Luxman L200 series.

 

Schematic:

The servicemanual of the Pioneer SA-420 click here

Sound:

Sound is very good due to the fact that there is no tone-amp involved. Heatsinking inside the amp is ok.
The Pioneer SA-420 amp is very well built and the schematic diagram shows a good electronic design.
The parts used inside are of very good quality. After many years of service all parts will be ok.
To improve the sound and specially the bandwidth of the amplifier at half or full power, you can replace some power-rail
capacitors and some capacitors in the main amp to get a more stable sound image.
Specially the lows will benefit from addressing this issue.
Finally you get a fine amplifier, although moderately powered, of exeptional sound quality, and that for very little money.
This amplifier will be able of driving all big medium and high efficiency speakers and of course bookshelf speakers.
The main amplifier has no protection circuit involved, so be carefull driving this amp at full power
or below 4 Ohms total speaker impedance.

 

Modifications:

The power supply can be improved by using bigger capacitors. Use ie. 10000 uF 35V.

The lamps may be replaced by LED's, with a 3k3 Ohms resistor in series. I used green ones.

You may replace some capacitors in the amp and eventually the coupling caps in the pre-main amp connection.

You may insert a small protection circuit.

 

 

 

© Hans Hilberink - PE1MMK ® 2003 - Last update: 25-10-2011.