Noise coming from subwoofers and centre channel

Nice detective work, and at least at this point there’s a loop that involves the AVR and/or amp. If it’s me I’d try the simplest thing first that’d be a cheater plug on the AVR, then on the amp, and then on both (if necessary) and see what happens. You could also consider contacting the fine folks at Hegel as they may give you a very quick and effective solution rather than spending time/$ trying different things. I’d be interested to hear what you find.

This might be overly simplistic, but what about just trying some cheater plugs?

One thought — you didn’t mention if you’re using a power conditioner/surge protector, which I would hope you are given the cost of your system.  If so obviously the conditioner would be plugged into the wall with a 3-prong plug so wondering if then using a cheater plug on the projector is a non issue?  If you’re not using a power conditioner that’s definitely something to address, and depending on how its designed may also help alleviate your noise issue without a cheater plug.  Just some further thoughts FWIW and glad you’ve at least identified the culprit and gotten rid of the noise — that’s gotta be a huge relief!

I only use a powerbar...I am happy to have made the discovery but I do not want to put my system and our security at risk....with the cheater plug...

But, your entire system already is at risk as you’ve got no surge protection and there are many here who’ve told tales of losing expensive equipment plugged into the wall.  I have a vey transparent Wiremold power strip, and when I wanted to add power conditioning and surge suppression I just got this and plugged my power strip into it and my whole system was protected on the relative cheap.  I still question if your power strip is plugged in with a 3-prong plug if the cheater plug makes any difference — I don’t know the answer but maybe someone like @erik_squires or someone else does.

https://www.usaudiomart.com/details/650064731-audience-adept-response-ar1p-power-conditioner/

FWIW.

I only use a powerbar...I am happy to have made the discovery but I do not want to put my system and our security at risk....with the cheater plug...

But, your entire system already is at risk as you’ve got no surge protection and there are many here who’ve told tales of losing expensive equipment plugged into the wall. I have a very transparent Wiremold power strip, and when I wanted to add power conditioning and surge protection I just got this and plugged my power strip into it and my whole system was protected on the relative cheap. I still question if your power strip is plugged in with a 3-prong plug if the cheater plug makes any difference — I don’t know the answer but maybe someone like @erik_squires or someone else does.

https://www.usaudiomart.com/details/650064731-audience-adept-response-ar1p-power-conditioner/

I suppose it’s also possible that installing a power conditioner may fix the problem with no cheater plug needed. FWIW.

I still don’t have an answer that if the power strip is plugged in via a 3-prong plug and the projector is then plugged into the strip with a cheater plug if that’s still an issue.  If the power strip is grounded I don’t see why plugging a component into it with a cheater plug would be a problem as it’s already grounded through the power strip.  Am I missing something here?