It's not possible to connect a Sonos One to a TV via HDMI? - It has no audio-in ports for such a cable connection? If you’re maybe referring to a Sonos Beam (gen1), or similar Sonos HT product, then it’s perhaps something the TV is doing. Possibly something to do with ‘power-saving’ on the TV, and CEC auto-power-sync, perhaps?). At least that would be my initial guess here, but maybe check with the TV user-manual, or the manufacturers Support Desk.

Thanks for your reply. You're correct it's the Sonos Beam Gen 1 and it's not a TV issue as I mentioned in my previous post. Since I disconnected the Sonos this issue never happened again and the TV volume remained as left. When I did reconnect the Sonos the issue started again. Pls help. 

The internal TV speakers are not using CEC - so try switching off auto-power sync for the CEC enabled devices connected to the TV, as suggested, and see if that solves the issue. You may need to check the user-manual, or speak with the TV manufacturers Support Desk to establish how to disable it on the TV.

@PBL770 
Just as an example of the feature I’m referring to, here is the setting on an LG TV (see attached screenshot). Find the equivalent on your TV and see if switching it off solves your issue. If you can’t find it. then check the TV user-manual etc.

It’s certainly more likely to be a tv “feature” or a tv setting, or Beam owners around the world would also be posting.

Unless, of course, Sonos staff can answer the question:

“Does a Sonos home theatre device default to a particular volume when it enters/exits a low power mode condition? If so what is the volume?”

My Beam’s volume control in the Sonos App stays at the same volume level, with the TV either ‘on’ or ’off’ and plays audio (TV/Music etc.) at that volume (it’s usually set somewhere between 35 and 40).

Hi @PBL770 & @nik9669a 

I concur.

No - it has no need to as it has direct control over it’s own digital amplifiers so can prevent any power-on/datastream-start spikes that the muting behaviour from the TV is presumably trying to prevent. Also, what @Ken_Griffiths said:

For what it’s worth, I see this behaviour occasionally with my own Sonos Amp and HiSense TV, but the TV has a fast-power-on feature and I only see the green mute indicator on the Amp when the TV does a longer power-on sequence for some reason instead - presumably, my TV doesn’t feel the need to try to protect against spikes because those circuits aren’t turned off in the first place as the fast-power-on feature is, I assume, akin to the sleep mode of a computer. Once audio starts on the TV, it only takes a couple of seconds for my Amp to unmute and for sound to return - no manual adjustment is needed, in my case.

@PBL770, if you haven’t tried already, I heartily recommend a hard reboot of your TV - please unplug it from power for at least a couple of minutes. I’m in agreement with @Ken_Griffiths on the CEC side of things too - the TV will be trying to unmute the Beam (why wouldn’t it?) so I too think there could be another device causing a conflict, at least during the start-up process of the TV. When you manually adjust the volume back up, do you have to use the Sonos app, or will the TV remote work?