I have a Denon 2020 AVR (X2700H model) and I tried hooking up my RTX 3080 to its 4k 120hz/8K 60hz HDMI 2.1 Input then hooked the HDMI 2.1 output to the LG C9. Can confirm the Denon AVR is absolutely bugged just like the article says. The screen goes black every 10 seconds or so and loses signal then comes back on only to go black again, rinse repeat.
Configuring things the opposite way around GPU ---> TV HDMI1 ----> TV HDMI2 (eARC) ----> Denon eARC seems to work fine.
I contacted the retailer i bought the AVR from told him about the issue and he in turn contacted Denon directly. Today he forwarded me a reply from Denon's sales rep:
Some new gaming source devices that support 4K/120Hz output may not work fully with Denon (or Marantz) 8K AVRs. You may discover this incompatibility issue due to a HDMI chipset mismatch between the devices. When the affected system is connected to the AVR via 8K HDMI input and set to output at 4K/120Hz, and the AVR’s 4K Signal Format option is set to “8K Enhanced,” you may not see the system’s source video on their display, and may not hear the system’s source audio processed through the AVR. This problem is only present when a display that supports 4K/120Hz is used.
We are currently investigating the issue further and will offer a permanent solution at a later date. Meanwhile, we would like to provide a couple workarounds to prevent the issue in its current state:
- You can connect the system to the display directly via HDMI and use the display’s ARC/eARC functionality to feed the native audio back to the AVR using the connected HDMI cable between the AVR and display. This will allow users to decode the native audio format sent from the source. With this method, the display’s CEC/ARC option must be enabled as well as the AVR’s HDMI Control and/or the AVR’s ARC option. In the AVR, this option is located within the GUI under “Video – HDMI Setup.”
- Another workaround is to leave or change the source’s video output to 4K/60Hz instead of 4K/120Hz until a permanent solution is available. This will ensure reliable communication between the source, the AVR and the display. The source’s default is set to output at 4K/60Hz, so if no change was initiated out of the box, then nothing further needs to be done.
We apologize for this inconvenience and we are currently working tirelessly to release a permanent solution so you can enjoy the 4K/120Hz experience using the latest sources with your AVR. We will have an update soon regarding the timeline of a permanent solution. We appreciate your patience.
So it seems Denon are now aware of the situation and are looking for fixes but IMO they're probably gonna have to recall all the 2020 AVR's and either switch out the chipset inside or replace then entire AVR. Here's a video which best describes the issue: