The harmony (micro) Dac is the only Dac I know so far that allows one to choose which clock to go with, I2s vs local (dac) clock. I try both and it seems local clock option yield slight better SQ but I won’t swear to it. Both units (U18 & micro Dac) might have similar grade of clock. I use Ifi Ipower X for the micro Dac and I use 0.5m DHL hdmi 2.1 cable as shown earlier.
With that said, @sns, what you have said below confuses me a bit and please provide some clarification.
By the way, I have Harmony with Denafrips Gaia DDC, sync’d to Gaia via Tubulus Ximius I2S cable.
What clock option you have chosen in Harmony Dac to sync., local (dac) or i2s clock?
This superior to optimized usb vis Sonore OpticalRendu via Audioquest Diamond usb.
This makes sense. The U18/micro DAC via I2s also outperforms the usb (galvanized isolated) input on micro Dac BUT that is because of the weaker source (Wiim Ultra; but still very good when combined with DDC). That is why I am thinking about the upgrade.