Confused about adapter for RCA to BNC

Some adapters are 50 Ohm and Some are 75 Ohm so be aware if you use an adapter,  you need a 75 Ohm 

I would go with a factory made cable

https://wireworldcable.com/products/starlight-10-coaxial-digital-audio-cable?variant=47931732623656&country=US&&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&srsltid=AfmBOooTBKmwaWEZNWx1JI9tvdkcsAFhzzEJ4_cDKSOSLG__ZoD2CX6mpno

They make higher grades , this is an example. 

If you order one they are available as BNC to RCA or RCA to BNC.   If the source is RCA and the DAC is BNC you want a RCA to BNC.   It has to do with the grounding I believe. 

@stuartk confirm the specs on your bnc cable to make sure it is 75ohm before you buy adapters 

I’d rather use AES from transport to DAC or a proper 75ohm coax cable and not introduce any adapters unless you have a fancy and expensive bnc cable that you can’t part with. I wouldn’t add variables such as adapters to compromise the results.

As @audphile1 has suggested, and my favorite, is AES if your DAC has an AES input.  This comes after trying everything else.

I have used any number of 75ohm, off-the-shelf, BNC-RCA and RC-BNC adapters (often marketed for video use) for S/PDIF connections without any problems.  Never paid more than $2 for any of them.  What have got to lose?