Technical question regarding sound quality from different zones

I’m hoping someone with a technical understanding of how the signal is affected by DACs, etc. can explain why I believe I hear better sound quality when using my Oppo 203 zone compared to my Marantz SR5010 zone.

My core is installed on a Mac Mini with 10.10.5 which is using HDMI output to my Marantz SR5010. I have Exclusive, and Integer modes enabled, and Convert to PCM.

I enabled a zone for my Oppo 203 through my network which also connects to the Marantz through HDMI.

I haven’t enabled any DSP settings in Roon, and the Marantz has Audyssey enabled.

Can someone offer an explanation for why I believe I hear a noticeably cleaner sound through the Oppo ethernet zone as opposed to the Marantz HDMI zone? Both zones ultimately play through the Marantz.