help! no sound

Hello mcanaday!  Cables are the least reliable things in most sustems. Particularly the ones with phono (RCA) plugs used in most interconnects. You mention you were putting a system back together. Just this evening I was putting a system back into operation following a flood and I found two cables that were intermittant and had to be wigged jusst right to get the signal thru. I have lots of cables and replaced them. I am a very careful guy and these were from a reputable company. But they do suffer from a lot of pulling and pushing and go bad somtimes. Check them first. Good luck! 

I didn’t get that in the OP you were trying to use headphones.  I am also still confused what happens when you run the CD player directly into the amp with RCA cables.  Are you getting music or what?  If you are successfully playing music from the CDP into the amp then the problem is the DAC

I thought the OP was pretty clear that he also tried the RCA output from his CD player (which works fine into the speaker amp) and this gives the same no-sound results as using the Bifrost DAC. Definitely sounds like the Lyr headphone amp is the problem.

well I beg to differ, i found the original post confusing in that first there is a statement that sound is produced through the speakers from the cd player followed by a statement that there is no sound from the CDP.  I'm not trying to be pedantic, but I've been through a few rabbit holes on this forum when the original issue is unclear

The OP had a second post that provided more information. That's the one where he said he used the RCA outs of the CD player to his speaker amp, which works without issue, and runs the CD player's coax out into his Bifrost DAC which then fed the Lyr, and didn't work. In this post he explains he did try the CD player's RCA output directly to the Lyr with the Lyr still not producing sound.