Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
sampling rate of 44.1 kHz, this equates to a potential drift of samples per
second. Even if two word clocks start at precisely the same time, they are likely to drift at
different rates and thus will eventually be out of sync. To avoid the errors that result from word
clock drift, you need to synchronize the word clocks of all your digital devices. There are three
basic strategies for word clock synchronization. The strategy you choose depends on the
capability of the equipment you are using.
The first word clock synchronization strategy is to slave all your digital devices to a
dedicated word clock generator. Any time you can go with a dedicated hardware solution,
chances are good that the hardware is going to be pretty reliable. If the box only has to do one
thing, it will probably be able to do it well. A dedicated word clock generator has a very stable
word clock signal and several output connectors to send that word clock signal to all the devices
in your system. It may also have the ability to generate and sync to other synchronization signals
such as MIDI Time Code (MTC), Linear Time Code (LTC), and video black burst (the word
clock equivalent for video equipment). An example of a dedicated synchronization tool is shown
in Figure 5.26.
Figure 5.26 - This is a dedicated synchronization tool from Avid
External word clock synchronization is typically accomplished using low impedance
coaxial cable with BNC connectors. If your word clock generator has several outputs, you can
connect each device directly to the clock master as shown in Figure 5.27. Otherwise you can
connect the devices up in sequence from a single word clock output of your clock master shown
in Figure 5.28.
Figure 5.27 - Synchronizing to an external word clock generator with multiple outputs