@chedwin I don’t think it’s necessarily “encoded” (yes, there’s definitely other terms, but we’ll work with that for now 🙂 ), but more of a situation where the noise is coming over from the PC (obvious source since it’s the only new component in a previously quiet environment) and getting through to the analog stage, effectively getting around the digital buffer and packet inspection. When you think about it, it has to be a harmonic of the fundamental, and with video cards, that’s quite a few orders away to be in the audible range. If it’s that bad, just think how bad the fundamental must be. Would love to see a FFT on the noise.
@sb-woo If you unplug the PC and AVR from the outlet, but keep the HDMI or whatever patch cords you are using plugged in, can you measure the resistance/continuity between the computer and AVR cases? That may help deduce what’s going on.