I use the Topping D10 192 khz USB DAC/DDC which is only $100 USD to feed Digital MPX to my Broadcast Warehouse TX300v3. It has a SPDIF coax out, not AES/EBU. This is not a problem at all because I then use an AES/EBU digital impedance transformer adapter made by Neutrik. It is the NADITBNC-M Female 75 ohm BNC to XLR 110 ohm output version and is $45 USD. This solution works perfectly and flawlessly. The Topping D10 was personally measured to have flat audio response to almost 80 khz on it's DC coupled analog output. No tilt compensation is needed at all in Stereo Tool. Useful if you ever need to use the analog outputs to feed MPX to an older transmitter. Long story short, after testing numerous USB 192 khz DACs, the Topping D10 was the best all around winner. Not many DACs out there have analog and digital output, this one does! I have the older D10 model which has been replaced by the D10s model. Physically they are the same, but with a different chip and ever so slightly better S/N.
Just a technical question: why is this impedance transformer needed? It basically transforms spdif coax to AES EBU?