USB DAC Dumb

Yes im sure there is , check at Fryes or another electronic parts store, Heck Best Buy might sell a cable or adapter.

Matt

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.    

Just to clarify. 
I want to use the DAC in the headphone preamp.
The headphone preamp has a USB input, a pair of RCA inputs and a pair of RCA outputs.