USB DAC Dumb

If the CDP has digital out, YES, it might be possible to send signal to your headphone amp/DAC assuming compatibility (with or without an adapter) between the output of your CDP and the input to your DAC.  IF the CDP only has RCAs outputting an analog signal as would go to a pre-amp or amp, then I don't think you will be able to do it.  Got to be able to access the digital stream in the CDP and send that to the DAC.  Or so I think.    

david - to me there are 2 questions that need to be answered to address your original inquiry about using an older CDP w/the DAC in your HP amp...1) Can your CDP provide a digital signal that the DAC in your headphone amp can process? 2) If the CDP does have a "Digital out", can you find a way to get that signal into the USB port on your HP amp?  If the answer to both of those questions is "Yes", then you should be able to listen to that CDP though your headphones using the DAC in the HP amp.    If either is "No", you might still be able to listen to the CDP via the HP amp using conventional RCA-type interconnects but I suspect this won't take advantage of the DAC in the HP amp.   Hope that makes sense.

Mahler's point is Question 2 in my previous post.