Jitter is the phenomenon of a drift in the digital audio data delivered so that it does not precisely match the sampling frequency, causing confusion in the receiving equipment as to the appropriate value of the sample. A host of allegedly audible problems with CDs and other digital formats have been laid at the feet of jitter. In my view this is considerably overstated. Jitter was a problem in the early days of all-digital production studios because each piece of equipment would have its own circuit to generate a digital clocking signal, and these would tend to drift apart from each other. The results were sometimes subtle, as when they resulted in dropped samples (due to the receiving device reading a little more slowly than the source). But they were equally likely to be obvious as a result of the source running more slowly than the receiving device. From time to time a 'zero' sample would result, producing an audible click in the sound. Professional studios have long-since overcome these early problems by providing a standard clocking signal source which controls all equipment, ensuring that they remain fully synchronised. For consumer equipment connected using the universal S/PDIF standard, there is equally no problem. The source always runs in master mode, providing the clocking signal to the receiving device (for example, a home theater receiver) which always runs in slave mode with its timing locked to the incoming clocking signal.