I have previously posted on this forum that to get analog audio into the ATEM TVS AES/EBU input, the cheapest way to do this is with the Behringer SRC 2496, which will convert analog audio to AES/EBU.
http://www.bhphotovideo.com/c/search?Ntt=SRC2496&N=0&InitialSearch=yes
$163 at B&H Photo. This still makes the ATEM TVS an incredible purchase - no manufacturer - new or used, can come close to the price of the ATEM TVS.
Bob Zelin