USB DAC Dumb

Unless there is such a thing as a coax or optical to USB adapter, you won't be able to.  Have you looked for that?

Mahler's point is Question 2 in my previous post.

D99, Your CD player probably has a SPDIF output.

Sending SPDIF Input to the DAC's USB input cannot be accomplished by a simple cable type of adapter/converter

You will need an electronic converter. 

USB - SPDIF converters are common, but I do not know of any SPDIF TO USB converters

Are you sure your amp does not have any other type of digital input? Such as optical

What amp do you have

Check out the Mutec-3 or even less money the Mutec-1.2

Williewonka 03-20-2016 9:23am edt
Sending SPDIF Input to the DAC’s USB input cannot be accomplished by a simple cable type of adapter/converter

+1.

Outputting a USB signal requires either a computer or a device that emulates the USB-related functionality and processing of a computer. A converter having that capability would certainly not be a simple adapter. I am not aware of any such converters, but if some exist I wouldn’t be surprised if you would be better off in terms of sonics as well as cost if you simply connect via analog, and use the player’s internal DAC.

Regards,
-- Al