Need a high quality spdif to usb converter

Land read on that box only works with a computer 

The Mutec MC3+USB will convert spdif coax, aes/but and Toslink to USB or USB to spdif.  It is a master clock but very versatile.  Not cheap but is a great box.  

While USB is better than S/PDIF, this device is Class 1 USB, meaning not asynchronous.  

The performance gain of USB only happens when your DAC can control the incoming rate, which can't happen once you have gone to S/PDIF.  There's little upside unless the client has no other input.  Also, check that the sample rate is acceptable. 
 

Normally DAC controls this incoming rate by sending back the signal - not possible with S/Pdif, therefore it has to be synchronous USB, that is pretty bad from what I've heard.

I would look at the Denafrips models, they do a great job. The Iris is the entry level which is still very nice. Then it moves up to Hermes and Gaia. 

Musician Audio has similar unit which I guess are made in the same factory. Pisces, Leo, Phoenix in ascending order. 

Matrix and Singxer used to make really great DDC units, I'm not up to date on those these days but might be worth checking as well.