Alright guys, having a really frustrating issue and hoping someone can help..
I've been using Home Theater PC's for twenty years at this point, and never seen this issue a single time with any other brand of AVR. Basically, if I have my HTPC plugged into my RZ-50 via HDMI, and I try to use any of the Pre-Outs, there is significant noise that carries from the AVR to the external amplifier, and it affects ALL HDMI inputs, not just the one being used for the computer. If I use the internal Onkyo amplifiers, everything is quiet as a mouse, which makes zero sense to me. If I turn the computer off and use Xbox, PS4, or any other HDMI input, the pre-outs are clean as a whistle. I have tried using a different PC, and the result is identical.
I know some of you are going to say, why not just use the Onkyo amps? Basic answer is, I like my external amps and want to use them and shouldn't have to compromise on this in my opinion.
One diagnostic note: If I plug either PC into my Monster HTS3500 line conditioner, the "noise" is cut significantly, but not to a point where I'd be happy with the outcome permanently.
What would you do if you were me?