Stereo matrix surround decoder

How it works

This analog matrix circuit takes a stereo input and produces four outputs for separate power amplifiers. Sum and difference information can create a wider spatial effect from suitable stereo material.

The extra channels are derived from the original two channels; they are not independently encoded digital surround channels. The circuit does not decode modern Dolby Digital or DTS bitstreams.

On the bench

Connect the outputs only to amplifier inputs. Keep channel levels consistent and test with a known stereo recording; the effect will vary with the recording’s phase and stereo content.

Resources & provenance

Rewritten from the original circuits/aum/lj3on1t_aum012.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.