My experience is quite the opposite. And trust me, my FLAC rips are high quality rips - my thread.Ah... interesting!
In my setup, using a stone-age 1996 Sony as CD Transport either directly into the DAC or via DDC (Gaia) sounded worse compared to playback of ripped FLAC fils via Auralic Streamer --> DDC --> DAC. That's why I was asking.
The old Sony CDP had TOSlink only, though.
As for CD playing, source material matters - If the CD is of bad sound quality, so will the sound coming out the audio gear. As a music collector, I own a lot of quality sounding CDs (aka "audiophile" type CDs). Some examples are > here and > here. But there are others. I tend to stay away from those early CDs release CD titles of the mid 80s and 90s and opt for the better versions where possible. Another example are the Mobile Fidelity SACD releases I have. Where these are hybrid CDs, they will play on a standard CD player via the 2-channel layer of the disc. Still, they sound far better than the earlier CD releases.
Point here is the sound quality of the CD matters in how good the playback is..
I can't o Rotel to Iris, because...I'm sure you tried the Rotel-->Iris-->Pontus route as well?
1) the "Iris" only takes a single USB input, whereas both the Hermes and Gaia take both a USB and coaxial input.
2) the Rotel only provides two outputs - a pair of RCA outputs (using the internal DAC), and a single coaxial output (bypassing the internal DAC / thus transport only).
That's me. YMMV