Krell Showcase preamp , how to connect headphones ?

Problem : The Krell Showcase preamp does not have a headphone jack. How do you use headphones with it ? 
Connection: I plugged my 4K player coaxial out to the Krell Showcase Digital Audio inputs 1.  
Krell Tape Out L-R connects to a Schiit Magnus 3+ headphone amp using RCA cables. 

Operation:  On the Krell , I click on DVD. The display says Coax 1. I click on the Tape monitor. No sound is output to my headphones.  

The Krell Showcase manual does not mention how to output audio. 
I will appreciate advice how to resolve. 

Happy New Year,
I wonder if the tape out is muted in normal operation unless you do something with the unit.  Did you try running from the normal left and right analog output jacks to see if anything comes out?
I do not think you want to click on "tape monitor" because that will route the "tape in" to the system. When set to "source," the tape out - in your case, your headphone preamp - should receive the output of whatever other input is selected.

The tape monitor function is really intended to use with a three-head tape deck, allowing monitoring of a signal just after it has been recorded.
Thanks, I did try connecting the headphone amp to the preamp L-R output jacks. Still not working.  
I did try connecting the headphone amp to the preamp L-R output jacks. Still not working.

I'm not sure you understand how this should work. Or, maybe I'm not understanding you properly.

The headphone preamp input should be connected to the Krell's "tape out" jacks. Whatever source is selected on the Krell should then go the the headphone preamp -  but do not select "tape monitor" on the Krell. That should be left on "source."

Please try that and report back.
If you fed the signal from your source via analog interconnects rather than the digital input, would it work?
My 4K player only as HDMI out, Coax out. No analog out.
I would like to use my headphones with my CD player too, so I do not want to tap directly from 1 source and always have to switch cables between the CD and 4K.

I emailed Krell tech support today. Maybe they will have advice, not counting on it. I’ve never contacted them before.