tv: MacBook Pro to LG B9 to Denon via Sound Flakiness need settings and wiring check

OK, this setup has actually worked pretty well for three years, but lately, with Ventura, I’ve been having this problem:

MacBook Pro 2021 with Ventura
LG B9 (I thought it was a C9 back then, but its the slightly less nice B9, but the controls are identical)
Denon 2310Ci. This is a now 13-year-old (!!) Dolby 7.1 AVR

The trick I was using that since the old Denon only supports HD input, I would normally route all the inputs for the system through the AVR and then to the LG, but instead, I have to route the audio and video separately, so this is how the system is setup:

MacBook Pro 2021 with Ventura (which is new, so this could be the problem) with CalDigit TS4 (recently replacing the Razor Thunderbolt 4) so this could be the source of the problem via HDMI running at 4Kp60 (although there are rumors that 120Hz now works)
Alienware R9 via HDMI with RTX 2090 (I know, two generations old)
LG B9. This takes as HDMI input the MacBook Pro, Alienware and it also takes the output of the Denon 2310Ci so that I can use the onscreen menus for configuration

With this setup, the LG B9 actually acts as the center of the system, it of course puts the right video up and then it can route audio out via its own speakers, an ARC connection which is limited 1Mbps so it doesn’t support surround sound or via an Optical TOSLink that supports a compressed 5.1 output (it won’t do say 5.1.4, but the Denon only handles 7.1 so that’s a small problem

This setup has been working great, but lately, I can’t get any audio output from the MacBook Pro and sometimes the AVR would just shut down, so for those of you wondering, here’s how to diagnose things like this:

First just set the LG to television or Netflix, something that it does itself.
Then change the sound to internal speakers. If you don’t hear anything, then something is very wrong as this is all local to the LG.
Then change the Sound output to Optical for instance (or Optical plus Internal Speakers) and try the Television on some application that is onboard. If this works, then it is not the LGs problem.
Now start at the other end. Start up your MacBook Pro and see if the internal speakers work.
If this works, then direct connect the MacBook Pro from the Thunderbolt port using the HDMI converter (I have a Caldigit one) and see that work and you get audio. In my case, this didn’t work, so it is either the HDMI convertor or the MacBook (but see the step below, it turns out that CEC was silently switching to the a different input).
So time to go swap some HDMI converters I tried the original Apple HDMI connector and got HD at 120 Hertz in SDR which is great, but still no audio. As an aside, it is great to have an Apple connector around, it lets you see if these problems are because of third-party vendors. The interesting thing is that the next time I plugged it in, I got 4K at 30 Hertz which is what I was expecting
Then I saw that when I did switch to the Mac, the Denon would automatically switch to TV input which is set for Optical 1 but doesn’t work. It just says, EXT In and I don’t get anything, but it will work in DVR mode which is set for Optical 2. I am only using the Denon defaults as I found changing these really seemed to mix the thing up. It is 13-year-old firmware after all. So you have to go to Settings and find Connections > HDMI and turn off CEC.
I also tried the CalDigit DVI to HDMI converter and this worked although it did not pass HDR through it. DVI doesn’t have audio
So backing up I tried the fancy CalDigit connector instead of the Apple one with the CEC fix. Also, I discovered that you want to start the Denon in the Direct mode so there is no processing. When that works, then flip it one to the right and you will get Dolby to decode and for Apple, you get ProLogic II PL Height which is correct
The next thing is to check all the channels and it was very quiet. I tried all the different settings, but couldn’t get it to work. Back to using the LG base output and it was also very quiet when in multichannel mode.
So then I checked all the speakers and I discovered the left surround and left height were completely quiet. A check of the connectors in the back of the AVR showed that because it is just below my feet, the topmost connectors had come off, so I put them back in and all worked much better

The Morale of the Story: Be Methodical

So, there were at least three different problems:

There is something funky about the TV input of the Denon, but DVR works fine.
The speaker wires themselves had shorted out which caused the receiver to be flaky. I can now see why sometimes, the AVR spontaneously turns off. The solution is not to put your feet on the thing!
The CEC needs to be turned off with old equipment (and new, it is pretty unreliable).
Be methodical, start from each end of the chain, and enjoy your music