Hi @DuncB.

Thanks for reaching out and welcome to the community!

Let me help and check it for you.

The only supported configuration for a Sonos BEAM when using an HDMI connection to output sound to the BEAM is to connect the BEAM directly to the TV's HDMI ARC port. If the TV doesn’t have an HDMI ARC port, the Beam can also be connected via optical with the included adapter (The Sonos made HDMI to Optical adapter, aka the Songle. This is proprietary to Sonos and will not work for other audio equipment). We don’t recommend any other adapter that changes that connection type.

What type of connection is available on your TV?

Hopefully, someone who has experience with the same setup will stop by and be able to suggest a workaround.

Furthermore, some of the community members might provide their own opinion about this anytime soon.

If you have any questions or concerns, please feel free to let us know, we’d be glad to help.

There are a lot of threads in the home theater area of the forum, albeit perhaps older and further back since the release of the Arc, about the use of external HDMI switches that have optical outputs on them. You may want to try a search using Google for that phrase.

Bruce’s suggestion will only work for an external device connected via HDMI, if you want TV-sourced audio to work you are SOL and its time for a TV upgrade.