I did some more testing with the ARC ultra and QN93 with surprising result.

I already swapped the oem Sonos HDMI cable with a used one (unbranded) but I now bought a new HDMI premium cable to 100% rule it out (certified blabla, see link below) and no more sound cut! I did not believed it but it's now almost a week without issues. Kind of crazy OEM Sonos cable is such poor quality. I checked it twice but for me the issue was really the HDMI cable

https://www.hdmi.org/spec/premiumcable

And have you tried watching content with uncompressed Dolby Atmos like TrueHD or tried gaming on a console like the PS5 with Dolby Atmos enabled and tested if (with the new cable) the sound still drops out?

Why are Sonos not responding on any of these issues ???

it is set to bitstream input and now also set to pass through output. same sound glitch 

Because this is a community site, and not an official ‘communicate with Sonos’ site? And likely the only Sonos employees that do exist here are busy moderating the forum?

I now tried with another certified Ultra High Speed HDMI cable. The first one was a Belkin. Quite pricey… but still had dropouts in sound with uncompressed Atmos content. 
I bought another one, also certified. It was almost an hour without dropout in sound… but eventually it happened again. 
So which cable did you try?

Kind of mind-blowing the type of cable makes a difference... Sorry don't have the package any more but this is the label:

For me the issue was on an external hdmi source and also Netflix internal tv app with or without Dolby Atmos didn't matter but never had one drop after the cable change and I'm quite sensitive to it so I'm sure for me it's fixed now

I noticed today, that the sound drops out when streaming as well. I noticed after the drop out output has changed from HDMI-eARC to HDMI. 
 

I think the problem with Samsung is that there’s no way to force eARC on. There’s only Auto and Off. 

I really wish there’d be a fix…

I tried troubleshooting with chatGPT today. 
We talked about Input Signal Plus on the TV:
 

“Key Points

1. Input Signal Plus Disabled Does Not Affect eARC Audio

• eARC is designed to work independently of Input Signal Plus. Disabling Input Signal Plus on the eARC port will not limit its ability to transmit high-quality audio (e.g., Dolby Atmos, Dolby TrueHD).

• This is because eARC uses a separate, dedicated protocol and bandwidth allocation for audio, unrelated to video enhancements.

2. Input Signal Plus Enabled Can Introduce Complexity

• Enabling Input Signal Plus increases handshake complexity because the HDMI port now negotiates for both high-bandwidth video (Input Signal Plus) and high-quality eARC audio.

• While this increased complexity doesn’t inherently break eARC functionality, it raises the likelihood of:

• Handshake errors if the TV or soundbar firmware isn’t fully optimized.

• Cable-related issues if the HDMI cable isn’t capable of supporting both high-bandwidth video and eARC simultaneously (though you’ve mitigated this with your certified cable).

Does Enabling Input Signal Plus Increase Risks?

Yes, enabling Input Signal Plus on the eARC port technically increases the risk of handshake or stability issues because the HDMI port now negotiates for both video and audio, even if you’re only using the port for audio. These issues may manifest as:

• Intermittent audio dropouts.

• Fallback to lower-quality audio formats.

• Handshake delays.

However, in your specific setup:

• You’re not sending video through the port, so the negotiation for video becomes less relevant.

• You have a certified Ultra High-Speed HDMI cable, which eliminates most cable-related risks.

This makes the likelihood of issues in your setup much lower, even with Input Signal Plus enabled.

Should You Enable Input Signal Plus on the eARC Port?

Here’s the recommendation:

1. If Input Signal Plus is Disabled:

• eARC will work perfectly fine. Dolby Atmos and other high-quality audio formats will transmit without issue.

• Disabling Input Signal Plus minimizes handshake complexity, reducing the risk of rare errors.

2. If Input Signal Plus is Enabled:

• eARC will still work as intended, but the handshake becomes slightly more complex due to the added video protocol negotiation.

• With your certified cable and modern devices, the risk of problems is small but not zero.

Final Answer

• Input Signal Plus Disabled: Safest option with the least risk of handshake issues, and it will not affect eARC audio quality.

• Input Signal Plus Enabled: Works fine in most cases but introduces a small chance of handshake errors. If any issues occur (e.g., audio dropouts or delays), disabling Input Signal Plus is an easy fix.

If you’re not using the video features of Input Signal Plus on the eARC port, there’s no practical reason to keep it enabled, as it won’t improve audio performance.”

Have any of you tried disabling Input Signal Plus on the eARC port and see if it helps?

I can only speak for myself, Apple TV, Samsung TV, Sonos arc and now upgraded to ultra. I have had the drop outs since day one and I bought the arc when it came out and for me the only solution was when I bought the HDfury Arcana. It solved all my problems. I can’t guarantee that it will help you but it has been a blessing for me, even if it ment spending my hard earned cash on something Apple, Samsung, Sonos should have solved. But as as I mentioned in my earlier post it all boils down to Dolby MAT and that it isn’t not compatible between products. 

It’s just a shame, if I have to spend extra money on extra equipment to make already expensive equipment like the Sonos Arc Ultra work flawlessly. The Arcana isn’t cheap… 

Not sure I agree with the Dolby MAT thing. I know HBO also use Dolby MAT, and I had no problems watching House of the Dragon with Dolby MAT Atmos on. The real issue is uncompressed Dolby Atmos like TrueHD and whatever Atmos output the PS5 does. 

Thank you, henebe for the Input Signal Plus write-up. I checked and found my eARC port was not enabled. I am in the same boat with Apple TV, Samsung TV and Sonos Arc Ultra with intermittent sound dropouts. I have made all the settings suggested in the forums. No difference when using apps on Apple  TV or Samsung TV. The one thing I haven’t done yet is to swap the provided Sonos cable. It is a very frustrating situation for all of us with this issue. 

Now after a week of no dropouts on my PS5, the sound decides to make a dropout as it automatically switches eARC off. Dolby Atmos wasn’t even enabled. It’s so random and frustrating when the TV decides to switch eARC off.

I got this reply from Sonos, when trying to address the issue:

”Thank you so much for reaching out with a reply and for further presenting your feedback and outlook on the current situation.
I understand you're looking to use ARC Ultra with your PS5.
Please note that ARC, ARC Ultra are configured to be used with TV connection and for playing music from a music service. For more details, fell free to check the user guide.

After evaluating your answer, you confirmed that there is no dropouts when listening to music or streaming movies on ARC.

To accomplish this, the only available workaround is to check with PS and see if any settings need to be adjusted because most likely other devices connected to your tv can interfere on HDMI port.

I hope you have a lovely day and stay safe!”

What kind of reply is this? Why are all the big companies pointing fingers at each other?

I’ve got a similar issue. Brand new Arc Ultra, Sub4, Era 300s and a Samsung S90D. I’m using a fire stick 4k max to stream content. Turning Input Plus on or off makes no difference. 
 

Are we screwed? Did I just dump thousands of dollars into a majorly flawed system?

Same Firestick and Sonos here, different TV and zero issues.

Looking at Samsung reports here I never considered buying one a good idea. My Sony does just fine.

It sounds frustrating! Since you've already tried different HDMI cables and other fixes, it might indeed be a compatibility issue between Sonos and Samsung. Unfortunately, I don't know if Sonos and Samsung are directly collaborating on a fix, but it's worth reaching out to both support teams for updates. In the meantime, you could try adjusting HDMI settings (e.g., turning off HDMI-CEC or switching to a different HDMI port), or using an external HDMI audio extractor as a workaround. Let me know if you need more suggestions!

I hopped on with support. They recommended a new hdmi cable from the TV eARC to Arc Ultra. I robbed the one from my Apple TV and so far I’ve had zero audio interruptions. This seems to have fixed it. 
 

Equipment:

Sonos Arc Ultra, Sub 4, Era300 (x2)

Samsung S90D

Amazon 4k Max Firestick

What HDMI cable did you use?

Have you tried playing uncompressed Dolby Atmos TrueHD content? 

I’ve been testing Dolby Atmos content via Netflix and Prime Video through the Firestick. I don’t THINK that’s uncompressed. The HDMI cable was the one that came with the Apple TV originally. This was an older gen ATV too (only 1080p). 

Update after a week: I’ve had ZERO dropouts since changing the cable so that seems to have been the issue.

No dropouts with streaming services and compressed Dolby Atmos here either. But the uncompressed formats still dropout for a second every 20 minutes or so. From physical 4K UHD discs and from gaming on the PS5 Pro. 
Sonos says this is s Sony PlayStation issue and they won’t do anything further to solve this.

The fact that you had this same issue with the original Arc and now the Arc Ultra leads me to believe this is more of a Samsung issue. More often than not, when someone reports audio dropouts from the Arc or Arc Ultra, it is from a Samsung TV owner.

So… the next TV I buy won’t be a Samsung, I guess… 

I have the nearly exact set up as you except I have the Sub Gen 3. My previous Arc would experience the occasional drop out. When I first set up the Ultra it dropped out on me. I pulled the power cord out of the back of the S90D and Arc Ultra and left them unplugged for a few minutes. Plugged back in and powered up and haven’t had an issue since, over 60 days now. 
Make sure you are using quality CERTIFIED HDMI cables. Amazon junk is often an issue. Quality cables aren’t cheap but they do make a difference. 

Good HDMI cables are important, but you can get them for a very reasonable price. I use KabelDirekt cables and they work great. Don’t pay a fortune for HDMI cables. It isn’t necessary.