Yes I did on the DAC's that were mentioned because its not a characteristic of digital (good or bad).
Sorry, I don't think I understand you. Sustain and decay are characteristics of sound, so yes, in that respect they are certainly not a characteristic of the digital system that may be rendering them. How can they be "missing in digital", or present with one DAC and not with another? The way you have stated it, to me implies that when listening with an Ayre DAC sounds cut out abruptly, and the natural decay of the sounds that were recorded (and which exists on the digital recording) was just not there via your system... While that same missing decay was present with the other DAC you tried. And how was sustain missing? From wiki: Sustain level is the amplitude of the sound during the main sequence of its duration. How can this be missing from digital?