Apple TV 4K not working through Yamaha RX-A2A receiver

Sounds to me like your initial attempt to run the ATV4K through the Yamaha was messed up because the ATV4K was looking for your old TV and any 'auto-reset' function there is didn't do the trick through the AVR.

Look, you've sprung for a spiffy new AVR that is designed to connect multiple video devices to an 8K TV with all the latest DolbyVision/Atmos goodness... don't give up so easily! If the RX-A2A CAN'T do what you've planned, you'll want to return it now while it's new, right?

Plugging the ATV4K directly into the TV on a new system like yours is a fallback option and a demerit against the AVR. Also, the way the ATV4K delivers Atmos audio is stressing your TV's eARC function and messing up your lipsync. Check out this Apple guidance on what you're doing - best practice is to use your AVR as designed: Set up Dolby Atmos or surround sound on Apple TV with a sound bar or AV receiver - Apple Support.

My advice:

1. 1. Plug the ATV4K back into the Yamaha - pick a fully-enabled HDMI input and VERIFY that the AVR's settings, through all the cryptic settings menus, are ready for full-blast 4K video and uncompressed multichannel sound coming in that specific HDMI port.
   2. Power up the AVR and TV before the ATV4K. I'll actually be surprised if the ATV4K, cheerfully looking for your new Sony, doesn't show up on TV as soon as the AVR sees your ATV4K power on.
   3. Next, on the ATV4K do the Settings > Video and Audio > Reset Video. This SHOULD grok the TV's preferred video setting and get the right resolution. From there, you can opt to enable a better gamma setting, HDR10=/DolbyVision, etc. NOTE: Lower down the settings screen, you should also see that the ATV4K is recognising that the AVR's Dolby Atmos is available.

If the video through the AVR looks flakey or can't handle the latest 4K content with wide-open DolbyVision, then we can test with shorter HDMI cables as part of a troubleshooting process :-).

What worked “perfectly” in the past with an older non-4K TV and older Gen Apple TV isn’t relevant because 4K signals are way more demanding than 1080p. There’s no way getting around that by paying more for cleverly marketed cables that have never been tested with Apple TV and don’t make any mention of it either.

Anyway, try this, just might fix:

• connect the Apple TV with a 3 footer (1 foot even better) to the Sony and then
• the Sony to your receiver with the shortest possible cable

For settings, see Use HDMI ARC or eARC with your Apple TV 4K - Apple Support

Good luck!

Anything over 3 feet in the Apple world is inviting trouble. Ignore the mumbo-jumbo on the packaging - those are not “ratings” but market-speak for stealing easy money from gullible types, nothing else. So chuck them and rejig your setup to accommodate shorter cables (The Apple TV itself can be strapped behind the TV with a cable as short as 1 foot TotalMount Pro Apple TV Installation System for Wall-Mounted Televisions - Apple).

Have you tried this:

• Apple TV to Sony direct HDMI using cable 3 feet max, or 1 feet strapped behind the TV and
• Sony TV eArc HDMI port to new receiver eArc HDMI port - start with 6 feet and work your way down until it’s good.

Once everything works with shorter cables, work out the placement and related aesthetics so everything looks nice and elegant.

No to anything “fiber optic” - just another gee whiz expensive gimmick that serves mainly to pick your pocket and little else.

Again, there’s no magic solution to this except shorter, shorter, shorter. You can get short HDMI cables from Amazon (or anywhere, picture is for example only). Ignore branding and ooh-aah package boasts - they mean nothing.

How long are the HDMI cables?

Great, thanks for updating!