Thanks for the answers, Torq!!
I have an iFi xCan that I bought through Headphone.com. It has two digital inputs. One is a 3.5 mm unbalanced which I am now using to connect via an adapter from my iPhone to my Etymotics. It works quite well. Based on your suggestion, I ordered a Belkin connects to avoid the adapter.
I also found and purchased a USB Male to 2.5 mm male connector that I have not yet received/ I will try to use it to connect the MacBook to the xCan.
I am not sure if I agree or understand your comment of digital not being balanced or unbalanced. My Theta Casablanca has an AES/EBU digital input which I understand is “balanced”. So, I don’t understand then the xCan input and if it will work from the MacBook or even I I can find one for the iPhone. I am sure I can find an adaptor from lightning to USB female.
I do not intend to use Bluetooth but as my wife has a pair of Sony blootooth noise cancelling headphones, I got this model as a precaution (if she ever intends to borrow it).
Thanks,
Carlos