I would GREATLY APPRECIATE IF SOMEONE with a a2020 or similar model would pop in a movie played through hdmi and pause it then turn up the volume to 0db and see if they hear any buzzing!
I have a Yamaha 2020 but use only the preamp section, which is connected to separate power amplifiers. With the Yamaha's volume control at maximum (+5), there is a slight buzzing and a bit of hiss audible within about two feet from the speakers. Beyond that distance or at lower volume levels (about -5) there is no audible noise from any input (HDMI or analog audio), whether a source component is connected or not. I just checked the system a few minutes ago.
The Yamaha is currently driving a power amp from the British manufacturer Quad (front L & R speakers). Also, I tested noise levels when the receiver was initially installed, using my usual Adcom amp (rated at 350 watts per channel at my speakers' 4-ohm impedance). With the Adcom there was no buzzing, only a very slight hiss at maximum volume at no more than one foot distance from the tweeter. The Quad amp is thus a bit noisier than the Adcom, despite the latter having a higher power output.
The surround channels, which I checked today as well, are driven by a different Adcom amp (200 watts/channel). The surrounds exhibit only a very slight hiss (no buzz) at maximum volume, again at no more than one foot away (any input, as stated above).
In normal use, playing the loudest movies or blasting music, and using any of the amplifiers mentioned, there is never any audible buzzing or hiss. The Yamaha receiver, in sum, has a very quiet preamp.