I do not what got into me. Unknowingly walk into MSB dealership and loan back a Premier DD to match with my already very good Discrete Dac. The experience is so engaging I am simply lost for words.
I thought I read somewhere that it will work. Manual only says Premier DAC and Ref Dac.
I like to ask which mode is most preferred passthrough or Filter?
Bit perfect blinking red led passthrough?
Filtered blinking green led with + logo highlighted?
Should be in Filter mode and you should see a + in the display. Make sure both have the latest software 
Yes the Discrete DAC pairs well with the Premier Digital Director and they work perfectly together.
The only time you should be using passthrough mode is when you are updating the Firmware of your Discrete DAC. In passthrough mode you do not get any benefits of the advanced digital filtering of the Digital Director.
Always use the Director with filtering turned on. The status light will be green and the plus sign on the display means that filtering mode is on.