@SkyNet404
I think what @sparkymarcopolo wants is to turn on his TV and not have the receiver that is connected to the TV’s eARC HDMI port turn on.
Which is entirely contrary to how (e)ARC is supposed to work.
The setting you describe anyway does not address that; it addresses only which screen the TV shows at power on, and I don’t think there is any screen that would ignore ARC.
@sparkymarcopolo has achieved his aim by turning off BraviaSync (CEC) on the TV; (e)ARC is dependent on the sending device having CEC turned on.
(Normally, it is dependent on the receiving device having it turned on as well, but Denon have a workaround for this, so it doesn’t need it.)
However, as he has found, turning off BraviaSync stops the Sony keeping up its end of the ARC bargain, so when he does turn on the receiver manually, the Sony sends no audio over the ARC.
Irregardless of ARC though, @sparkymarcopolo needs BraviaSync on so the Sony can automatically switch to the receiver when its output is detected.
So ARC is out, and audio from the Sony to the Denon needs to follow the suggestion of @rooobb to use the Optical Out. Which, as I surmise that the ARC triggering would still be operative, would also mean taking the HDMI cable out of the eARC port on the Sony, and connecting it via one of the other ports.
However, @rooobb‘s solution will require that the receiver doesn’t turn on when the optical signal arrives (if it does, it certainly won’t be CEC causing it) or we are back to square one.
And ideally that the Sony can control the volume of the optical signal - my 2015 Sony Android TV could, so it’s doable, as long as the more recent sets still support this.
However, the quid pro quo here would likely be that @sparkymarcopolo has to switch to this input manually.
And also the Sky box, unless he turned on HDMI Control on the Denon. Which might also be needed to switch the Sony automatically to the input with the receiver on it.
But which still shouldn’t cause the receiver to turn on automatically from the Optical signal, as CEC is an HDMI thing only.
Which only leaves HDMI Passthrough on the Denon to be set correctly.
The Denon manual seems to be saying that Passthrough would let the signal from the Sky box go through to the TV even with the Denon in standby, and wouldn’t take the Denon out of standby.
Which is fine if it’s what @sparkymarcopolo wants - that even the Sky box should not fire up the Denon Audio unless he wants it to. But he may need to turn Passthrough Off if he wants the Sky box to automatically start the Denon playing the audio.
I think the above will meet @sparkymarcopolo‘s requirements, though it will unavoidably require manual switching to play the TV’s audio over the Denon.
It may well be that the best solution is to go back to the original configuration, switch BraviaSync back on, and maybe HDMI control on the Denon as well, and resign himself to just one manual action, which is to switch the Denon back to standby when the Sony TV is switched on.
As I can’t figure a setup without at least one manual step, and this is actually the simplest.
My favourite bedtime reading is a Sony product manual…
