That is the way ARC works, it’s not a choice made by Sonos.
 

If you’d prefer, you could connect your Arc with the optical cable, rather than the ARC connection, and you could do what you want without issue. You would, of course, need to use that optical to HDMI ARC adapter. 

Many thanks. How much and what do I sacrifice for using the optical? There must be some benefit in using the HDMI through the eArc port or otherwise there would not be so much publicity around it. I’m by no means an expert but my setup is not cheap and I struggle to understand/accept that this is not an “issue” for most users - my sense is that I am not the only want who likes to have music playing with the tv on without having to sacrifice the sound of one equipment over the other… many thanks again

jnamaral,

Using the optical adapter eliminates some of the more advanced surround modes that are available only over the HDMI connection. There are also some control integrations, such as a common power button that are not available over optical.

I don’t know what it might be called on the AG9, but you could try disabling “CEC” on the AG9. This will disable communication over the HDMI, such as the common power button. However, CEC might be used for other functions that you will want to keep. Each TV is different in this respect.

CEC can be useful and it can be a pain. The overall idea is to simplify user control by enabling one button options. For example, pressing a single power button on the cable remote or DVD player can turn ON all of the components and select the appropriate input on a receiver. Setup can be much easier because components can announce themselves to each other. If you have a ROKU, you may have noticed that the Volume buttons on the ROKU remote control Arc’s Volume and this coupling did not require any user action. This is likely true for your AG9 remote too. Channel +/- on the SONY remote will probably operate the cable box and change Volume on Arc. On the pain side is the middle of the night cable box firmware update that ends by turning ON the cable box. CEC will get wind of this and, thinking that you want to watch TV, and will turn ON the system.

There is also an option in Arc to disable TV Autoplay. Try turning this OFF.

Many thanks. It sounds disappointing to have a state of the art soundbar and tv and be stuck with using an “older” technology or otherwise not being able to benefit from the latest technology at least. is this something we should expect to be addressed in a future androidtv / sonos update for instance?
 

My tv has a optical line-in so the question is whether I should use that or the eArc with the adapter. Any difference? 
 

I do watch tv and have music playing around a lot. Starting to get the feeling that I could have managed with just a pair of fives for better music and wait for Sony to come up with a way to sync my ones with my tv (tv as main speaker). Thank you all for the help

A good rule of thumb is that everything is obsolete before it leaves the factory. One must simply wait until the technology that one needs becomes available. As an example, I’ve put off replacing my ancient phone for a few years because I don’t need to play the latest games and I was waiting for some technology to come out of the lab. Finally (yesterday), I had to pull the trigger because some Apps that I need for work were no longer viable on the old phone. It got to the point where many web pages would not load because I couldn’t update the old phone’s web browser.

In mainstream home A/V the video connection scheme has evolved from Composite, to Component, to HDMI, to HDMI ARC, and currently HDMI eARC. Early HDMI cables cannot support 4K or 8K video. All of the cables look the same, but cables that are a few years old, cannot deal with the fierce data rates required for true 4K or 8K video. Further, it sometimes requires a few years for manufacturers to work the kinks out of new technology. CEC is an example of this.

The Playbar has an Autoplay function (on or off), I presume the Beam doesn't have the same?.

Don’t know about the beam but that option has no impact on my arc. It simply overides my sound option regardless of autoplay being on or off. 

BEAM supports Autoplay.

I'd not change over to optical, but would just turn off HDMI-CEC (Sinplink, Anynet) for the time I'd want to play music and hear my TV speakers.

i have the same issue,  if one usese the optical, what sound quality/funcionaltiy would i lose exaclty.  would one of them HDFury boxes solve the issue with no loss of funcations.

With optical you’d lose the ability to play Atmos and DD+. If you mean the HDFury Arcana, that would still rely on HDMI-ARC/CEC, so I do not think that is an option.

With an optical connection, you would not be able to play Dolby Atmos or multichannel PCM audio through the Arc and you would also lose voice control functionality.

The HDFury Arcana is an eARC device that allows external media devices to bypass your TV and send audio directly to the Arc. This is beneficial to users who have older TVs with audio passthrough limitations because their TV is only equipped with HDMI ARC.

but,,   will i still have atmos etc capability, and have the benefit of using the tv speakers instaed of the arc, which at the moment always defaults to the arc, even after selecting tv speakers.