Coax SP/DIF to USB..thoughts?

There is no such thing. A DDC will get you from USB, but It is two way tech making it impossible to convert a one way "to" it.

I have two streamers w//o USB and there is no way to get to it from there.

What makes you think I haven't played cable swap?? One variable at a time.

I suspect that this will make most coax sound better:

https://ifi-audio.com/products/spdif-ipurifier/

It did with anything I’ve thrown at it.

Agree going with a DDC like this…

https://www.vinshine.audio/product-page/denafrips-iris

USB is a relatively new requiment. It can with the need to connect computers to audio systems. Before this SP/DIFF was the connection. USB presents a completely different input to the DAC… the DAC must retime the bitstream. Which sounds better depends on your DAC and streamer. In general, if your streamer is better than your DAC then USB might sound better, and visa versa. Some DACs were produced specifically to be connected to computers and hence only have USB inputs. But of course some streamers then started to have USB outputs.

For contemporary and equal quality streamers and DACs SP/DIFF (or AES.. the balanced equivalent) is best. But you have to try both to be absolutely sure. I have very high quality equipment, there is really no substsncisl difference between the two, so I use the AES.

Avoid conversion. 

@ghdprentice   I think what you said makes a lot of sense. What connection and cable do you use from your Aurender? I believe your model has the option of all three connections, AES, Coax or USB. I would think the AES or Coax would sound better than USB. Interestingly,well respected models from Innuos only allow for USB, and I think that USB is perhaps a downgrade to Coax or AES...maybe not for their gear??