Line input on Studio 6|2 or Studio 6|8

I have a very basic and need am wondering if either the Studio 6|2 or 6|8 can perform this task: I am looking for a box that can accept UNBALANCED, line level audio (aka, approximately -10 dBu from an analog reel-to-reel or cassette deck) and output via USB. From the literature, it seems like these units only accept BALANCED inputs -- am I correct in that thinking?

An alteate for me would be to use the S/PDIF input on the Studio 6|8, though it seems like overkill to use a box a sophisticated box like this just for that simple purpose.

Thanks for any advice you can offer!