If you're watching through VLC, you can set the mix to stereo in the audio settings - perhaps there's a similar setting you can find? Not sure if you've got the

If you're watching through VLC, you can set the mix to stereo in the audio settings - perhaps there's a similar setting you can find? Not sure if you've got the tv's optical going straight into an amp. Some stereo receivers also have a "night mode" that can do this, you might find an older cheaper one with pre-outs or similar.