The "problem" is that Pd doesn't recompute the DSP graph when you *add* an object. Instead it recomputes the graph when you make a new signal connection (or when you delete an object, save a patch, etc.) So when you add the [dac~] object, the graph is not updated and it doesn't compute audio (yet).
So one solitary dsp~ object does not make a graph yet, correct?
Thänks, P