If you want to connect from an XLR to a mono jack (tip and sleeve only) both the screen (pin 1) and one of the other pins (2 or 3) must be connected to the sleeve of the jack. Otherwise you WILL get noise.

I assume your MacPro tosLink connectors are for stereo S/PDIF. If so, these should work at 96K. Eclipse does not support an ADAT format (4 or 8 channels) at 96K.