The Audiophilleo1 VirtualCable feature simulates the sonic effects caused by changing the length of an S/PDIF cable. It does this by slowing down the edge transitions, effectively shifting the zero cross-over point in time relative to cable reflections. Normally edge transitions are <700ps. Virtual Cable can increate this in 5 steps up to 15ns.
Why is this feature useful? Many audiophiles have observed that different types of digital cable can have a considerable effect on audio quality. This phenomenon is generally caused by impedance matching and electrical reflection problems.
"Digital” signals are, after all, simply unusually-shaped analogue
electrical waveforms, and fundamentally they interact with each other in
a manner similar to that of waves reflecting from the sides of a pool. When one electrical
reflection is superimposed on another, the receiving device may be uncertain
as to the exact moment when an “edge” or digital transition has occurred; this uncertainty is essentially a timing error, or
a form of
Such overlapping waves are mainly a concern at the moment the “downstream” DAC is looking for and evaluating the edge. If there are potentially troublesome reflections at that particular instant, the Audiophilleo1 VirtualCable can move them away from the edge by as much as 15 ns, in 5 steps.
The DAC can then measure the transition
perfectly, without uncertainly caused by a reflection, and “recover” the clock
from the S/PDIF signal with substantially greater accuracy. VirtualCable
even allows making these changes via