Data on hard disk has no timing. It goes thru all sorts of buffers to audio card or converter where timing is recreated. Different type of Hard Drive might have influence possibly reducing overall system noise (if lower power) but it won't affect serial stream. Playback program, or computer speed might affect data stream but they will change timing and not the data itself. Variation in time is jitter - removed by reclocker. I use wireless to completely isolate noisy computer from my system. Receiver, Airport Express is known to have a little bit more jitter than desired (258ps peak-peak while >50ps peak-peak becomes audible). Reclocking in my DAC reduces jitter to inaudible levels.
