20 W audio power amplifier

How it works

This circuit amplifies a line-level signal to drive a loudspeaker. Its output network includes L1, for which the original notes specify a current capability of at least 4 A. The inductor and associated components form part of the amplifier’s load and stability behavior.

The archive quotes 20 W output and a very low distortion figure. Those figures have not been reproduced during restoration and should not be treated as guaranteed performance.

On the bench

Check the amplifier device ratings, supply rails, heatsink, and speaker load before use. Verify idle current and output offset, then test with a suitable dummy load before connecting valuable speakers.

Resources & provenance

Rewritten from the original circuits/aum/lj3on1t_aum011.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.