To DDC or not to DDC. That is the question.

i understand ai can hear up to 50 khz, so you know you can fully trust it -- like 100% certain -- when it tells you what’ll happen in your system if you try a ddc...  

@mitch2  This AI description appears to be a mix of Mk I and Mk II. Whereas the Mk I USB card has the appearance of an off-the-shelf Amanero card, the Mk II does not. The important takeaway for Merason DAC owners is the Mk I and Mk II are not the same, and improvred USB performance appears to be a differentiating feature between the original version and its successor.

All of this is academic to some degree regardless, as a galvanically isolated USB receiver is certainly advantageous, but not a panacea in itself. Galvanic isolation performance varies with individual architecture and DACs with galvanically isolated USB routinely respond favorably to outboard USB isolators/regenerators. 

@ted_b - It appears you are correct. The USB input (and many other aspects) of the Mk II that I have was significantly upgraded over the MkI owned by the OP. Improvements affecting the USB input included capacitive galvanic isolation, precision oscillators for low-jitter, more through-hole components for shorter conductor paths and lower USB input signal losses, and PCB layout changes to reduce impedance and improve power delivery.

What I am hearing through USB is likely quite different (i.e., improved) from what the OP would hear, which is another reason that, IMO, the OP's money would be better spent on the upgrade than on chasing improvements due to input changes through a DDC. 

I have been very impressed with the Merason house sound signature and suspect it has much to do with their purposely optimized implementation of the Burr Brown PCM1794 DAC chips that use BB's (purchased by TI) advanced segment architecture which, to my understanding, is sort of a hybrid between multibit (ladder) and delta-sigma technologies. 

I have long used R2R DACs (my other DAC currently is an Aries Cerat Helene, an R2R design using multiple AD 1865 chips) and I find Merason's presentation a nice balance between the musical, natural, full-bodied, and tonally rich sound I enjoy from R2R DACs and the more precise and extended delta-sigma sound.  The Helene plays more grandiose and muscular but, when I am listening to the Merason the sound is close enough that I do not miss those qualities.  I just took the DDC out of the path and reinstalled my USB input directly from my Sonore streamer (using a Cardas High-Speed Serial Buss USB cable) and I perceive a bit more clarity and energy, without losing any of the musical qualities I enjoy. I am actually looking into the DAC2 upgrade, or possibly Merason's new Mountain DAC that I would use to replace both the DAC 1 MkII and the Helene.

Here’s a Hermes from TMR you could return I assume with a relatively small restocking fee if it doesn’t work out that might be worth considering…

https://tmraudio.com/products/denafrips-hermes-ddc-d-d-converter-9

@soix Thanks! 30 day no questions return policy makes this a tempting prospect! My only reservation is that the Hermes has no USB out and the USB input is the strength of the Merason.