Connectivity of an external DAC to an NAD M33 integrated amp

I have looked into this connectivity issue without answers as I have a friend with a new NAD M33 which evidently has an on-board DAC and I am keen to connect my Aqua LaVoce DAC to his system.  I personally think that on-board DACs might not be as revealing as better external DACs.  Can you fellas help out as to the proper connections to be able to connect my DAC to his NAD integrated amp and thereby bypass its internal DAC.  Thanks for any suggestions. 
The M33 digitizes its analog inputs.  I cannot see any reasonable way to bypass the on-board DAC.
this is the problem with combo units... hard to decouple the piece-parts sometimes... 
Thanks for the responses.  I can't imagine that the internal DAC in the $5K NAD M33 yields music as revealing as with the addition of a fine DAC, but that is just stating the obvious.  Thanks again.  
I had a similar problem.  I had the M12 (the preamp/DAC) which likewise had no upgrade path (other than to a better server than the BluOS module).  I ended up selling the unit because of this perceived limitation. 

In hindsight, I shouldn’t have sold it - as it was actually a very good unit and better than many like to believe.  I’ve spent more than I care to admit chasing incremental gains.