Keeping time

We're all aware that jitter in the digital audio stream is to be avoided. Jitter is all about timing deviations where the audio data isn't exactly where it is supposed to be in time. You can think of it like someone being early or late for their scheduled arrival time. For jitter to be audible it has to be unpredictably late or early. (If we know the data is always late or early by the same measure then it's easy to compensate). The reference for our digital audio data is called a clock. With every clock cycle, the digital audio system looks to see if there is any incoming data that arrived on time. If there is, life's good. If that data is slightly late or early, we get a "jerky" output of digits fed into our DACs. To make certain this doesn't happen we often add queues (buffers) where we collect all the on time, late, and early data together before passing them on to their final destination. This digital queue describes perfectly PS Audio's Digital Lens technology. Here's the thing. Data stored on a hard drive, streaming over the internet, or your home network don't have too much of a schedule to worry about. Think of them as travelers told to show up at a certain time and place where they are then expected to join a queue before being assigned to a time schedule. In other words, stored and streamed data don't have clocks that are important to their final arrival time. Thus, they cannot have jitter to worry about. Only when we enter the world of master clocks as dictated by (for example) CD/SACD transports do we need to worry about jitter. (In these cases the transport supplies the master clock to the DAC) Data entering a DAC must at some point fall in line to be properly queued up and marched in time so as to avoid jitter. Where that happens is all important.