For Gustard R26...which bang for the buck: DDC or LHY OCK clock?

I think the Musician Audio Pisces is a good value and worth a look.

https://www.amazon.com/Pisces-Interface-STM32F446-PCM768KHz-Isolation/dp/B0B7HPTMFW

@kereru Are you using the i2S output from the DDC?

@kereru How long is the Belden cable?  I’m using a cheap Monoprice HDMI cable that is only 6” in length and getting surprisingly great sound.  As you undoubtedly know, cable length is critical for i2S as it was designed as an internal connection inside pro audio components so the signal degrades quickly with cable length and most people who know more than I recommend 1 foot or less, which is why I went with a 6” cable and maybe a big reason why I’m experiencing such great sound.  I’ve also heard some people say they don’t notice much difference upgrading to a more expensive HDMI cable, which is why I’m like you and in no hurry to upgrade my current cable. If you’ve been using a longer cable and might like to try what I’m using it only costs $5.50 so what the heck?

https://www.monoprice.com/product?p_id=13578

I've read conflicting things re optimal cable length for digital cables, though expect it depends very much on the application. The main variable I've found for clock cables at least of which I've tried five is cable quality (conductor, shielding and termination quality) rather than length per se.

@kereru Clock or other digital cables are not the same as HDMI cables for i2S as per my last post.  For example, a digital interconnect is best at 1.5m, whereas that would kill an i2S signal.  The i2S signal is a different animal entirely and extremely sensitive to cable length.  Try the 1 foot cable and see what you think, or try the 6” cable I linked above for only $5.50.  Interested in your thoughts. 

The hdmi (i2s) cable would be 1.5 or 2 metres in length.

You should read my post above.  HDMI i2S cables need to be as short as possible, and 1-1.5m is very suboptimal.  Most people familiar with the connection recommend 1 foot or less.  Or, you can shoot yourself in the foot and use a longer cable.  I tried.