Looking to improve CD playback

i2s over HDMI is not an industry standard.  There are several vendors that use HDMI cable to transfer i2s, but that doesn't mean that any transport can be connected to any DAC using HDMI/i2s. 

For example, both Wyred4Sound and PS Audio have solutions that transfer i2s over an HDMI cable.  However, the pin configurations are completely different, which means that you cannot just connect a PS Audio transport to a Wyred4Sound DAC using i2 over HDMI.

Some companies also transfer i2s over an RJ45 cable (same as ethernet).  Their pin configurations may be different as well.

If you're really interested, I would check with the vendors on those products and ask them about their i2s/HDMI pin configurations to see if they are compatible.

You can always upgrade to different digital COAX cables and that will have a significant improvement as well.

mesch OP
I am motivated by the thinking that use of a NOS R2R DAC with CD playback might prove best

You are correct in thinking this, try to listen to an R2R Holo Spring Level2 or 3 dac, you can switch on the fly between it’s NOS and OS modes. (And it does DSD if your into that stuff.)
https://www.stereophile.com/content/holoaudio-spring-kitsun%C3%A9-tuned-edition-level-3-da-processor

And R2R Ladder Multibit is the best way to convert 16/44 24/96 or DXD all PCM and CD.

Cheers George

Isolate the CD player. Level the CD while spinning. Stabilize the CD itself. Get rid of scattered laser light. You’ll be light years ahead of everybody on your block.

Dan, I am sure your Arcam/DAC combination sounds great. As does my Arcam/DAC. I am just looking to maximize what I am getting from my CD collection. Also thinking now is the time to replace the BDA-1 while it will still provide me ~$700 on the used market, as I believe it remains a very good DAC. It just might be that I reconsider the I2S connection. 

Auxinput, I was concerned about there not being a standard for the HDMI I2S connection. I will consult with vendors regarding pin use. Given that the I2S input and other upgrades can be installed at a later date by Mirror Audio I am considering the purchase of the basic unit 1st and make decisions on upgrades after getting accustomed to the new DAC. It may be possible that Mirror Audio can configure the pin output to compliment a transport of choice. I will get to an understanding of this prior to making a purchase. Thanks!

George, Thanks for your support for my 'subjective' approach. Also the Holo Spring DACs are of interest to me as I have read reviews. Thinking the Tubador may better fit my budget. I am pretty sold on the R2R Multibit approach. Also looking to add tubes to the output stage which will drive my tube preamp.

Geoffkait, I will do my best to isolate the transport with consideration of routing internally generated vibrations and shielding from external ones.

mesch,
I have a BDA-1, and it is a fine DAC (I now have mine in my second system).  I also have a Bryston BCD-1 CD player.  Some years ago before I got into streaming, at the same time that I auditioned the BCD-1, I also auditioned the BDA-1.  Both at the dealer and and with a borrowed BDA-1, I experimented with a number of  lesser CD players and DVD players, including my own Denon 2910 DVD/SACD universal player hooked up to the BDA-1. It was no contest, even thought the BDA-1 was the technically superior DAC to the similar DAC built into the BCD-1, in terms of SQ, the BCD-1 just simply outperformed any of the combos I compared it to.  I came into the shop thinking about buying a good DAC, but wound up buying the BCD-1 instead.  When it came to spinning plain vanilla Redbook CD's the BCD-1 with it's rock solid Redbook CD only transport was the clear winner.  So the transport really matters.  A couple years later after Bluesound integrated streaming from Tidal I picked up both an original Bluesound Node and a BDA-1 to go with it.  It was and still is a very good combo, but couldn't quite match the BCD-1.  It was only after I started using a Melco N1A as my NAS (effectively as my CD transport) that I was able to approach the BCD-1 level of performance.