How are you grounding the Chord DAC? Is it directly to the mains earth?

Have you tried splitting the shielding of the Neotech cable and connecting it to the outer part of both RCA plugs?

If it were me, I would buy a ready made 5-pin DIN to RCA phono lead from Flashback sales. They are very well made, can be made to any length, use good quality Neutrik connectors and are not expensive.

https://www.flashbacksales.co.uk/aca...ca-cables.html