HDMI Multichannel on Mac: zipper noise (distortion) [solved: use power-of-2-buffer size]

On most 5.1 content with higher rate than 24bit/48kHz I get some sort of zipper noise distortion in most of the channels … somehow it sounds like a conflict of sample rates.
My system: iMac 5K 3,5 GHz >> HDMI >> Yamaha CX5100 Pre
Up until now I was playing multichannel recordings through Audirvana. All sample rates (up to DSD 5.1 converted to 176 kHz) played without a problem. I didn’t change anything on the Receiver side. If I close Roon and go back to Audirvana they play flawlessly.
Did I miss something?
Here are my settings: (all DSP off)

Try “use power-of-2 hardware buffer size”. One of my macs needs that to avoid audible artifacts using HDMI.

Yeah … it seems it’s gone now! No more artifacts.
Thank you! What a service!

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