What you're suggesting would work, but consider that your putting all the NAD pre-amp stage electronics in the signal line between your source and your HP amp. If you don't want to go Y adapters (which I don't agree would be a worse option, signal degradation wise), get a simple passive source switch to switch the output of the DAC between your NAD and HP amp. Sound quality, that would be your best bet.
I am not sure it would though? Isn't the tape loop just a passthrough connection?
Edited by nicholars - 1/25/13 at 1:35pm