Uberwaltz, a possibility that comes to mind, which could account for the symptoms you’ve noted with both the phono stage and the Oppo, is that the balanced cables are miswired such that their ground pin (pin 1) is interchanged with one of the two signal pins (pin 2 or pin 3) at one end. Thereby causing one of the two signals, as provided by the source component, to be connected to ground in the 2170. Which would adversely affect the performance (and eventually perhaps even the health) of the output stage of the source component.
If you have or can obtain a multimeter, check that each of the three pins at one end of each cable is connected to the corresponding pin at the other end. And also check that each of the three pins is not connected to either of the other two pins.
In doing so, it would be best to use a magnifying glass to view the pin numbers that are marked next to each of the pins, as their symmetrical layout makes it easy to confuse pins 1 and 2 with each other when comparing the two ends. And for that matter, perhaps the assembler became confused for exactly that reason :-)
Best regards,
-- Al