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WHO IS IN CHARGE? | Kent Morris
Photo by Sebbi Strauch on Unsplash
The clock, that immortal timepiece set as a regulator on our lives, is in charge. It tells us when to arise, when to eat, when to work, and when to sleep. It is in constant motion and brings solidity to that ethereal sense of time eclipsing our lives. Its face, whether in a sweeping analog mode or ever disappearing numbers on a digital scale, seems to make a mockery of our attempts to relish its presence. The clock never stops ticking, always reminding us of the fleeting aspect of life; how it slips past us even as we focus on its importance. For audio devices, however, the clock has a different meaning. It tells everything in the audio chain who is in charge and what to do and when. It rules what we hear.
Analog audio has no clock. Since the signal is pure energy modulation, it moves blazingly at roughly two-thirds the speed of light through circuitry and wiring. Time is irrelevant within analog audio. Digital audio, on the other hand, is very much beholden to the clock, because it is slow and simply represents audio, it is not audio. Audio must be converted into numbers and math must be accomplished for it to work. And since math takes time, time becomes the normative aspect of the process. When something arrives matters and it differs greatly from device to device and input to output. Knowing when to start and stop falls to the master clock. If the console is the only digital part of the chain, its internal clock is all that matters. However, when a digital stage box, a digital wireless, a digital LMS, or other console connects, their clocks may conflict and the result is often dropped audio packets, some large enough to be audible as missing sound.
Generally, the console’ s Analog to Digital Converter( ADC) is the preferred master clock in a simple system. Since the ADC is designed to be precise and stable, it fits the role well. Within the console settings, the internal ADC should be selected as the master and then other devices can be set to slave mode to ensure smooth audio delivery. When the system grows, though, an external master clock is in order. Capable of syncing not only audio, but also video, an external master clock is essential and uses its word clock output, often via a BNC connector, to connect to other devices. The clock identifies when each sample should be activated and provides the exact timing needed for the waveform to be reconstructed as the correct analog signal.
Knowing when there is a clocking issue can be a simple or complex situation. A dropout is the clearest signal something is amiss. Usually, there will be a two or three second gap in audio response without buzzes, pops, or other noises. The conflict is between two devices both seeking to be in charge of the timing. The disparity between them builds until both collide in a wide enough spread to cause the dropout.
The solution is to select one as master and one as slave. When on a Dante network, the
console’ s internal clock can be the master, then with Dante Controller set the console’ s Dante card to master and select“ Sync to External”. The Dante card can instead be chosen to lead by setting the internal console clock to slave mode for the Dante card. Then, using Dante Controller, set the console’ s Dante card as the master.
Once the system moves into a complex state with numerous clocks involved, the process becomes tricky as what appears to be a previously unknown glitch asserts itself during the service. Tracing the source is impossible during an event, making the network’ s log an essential detective tool. The log will register conflicts and issues on a timeline and may deliver enough information to be as useful as a fingerprint is at a crime scene. Tracking down the problem then becomes easier as patterns emerge, and culprits are apprehended.
Digital audio requires synchronized timing via clocking devices. Knowing when to use the internal clock and when to go external falls to the complexity of the rig and how stable the internal device is relative to the need.
Kent Morris Kent Morris is a 45-year veteran of the AVL arena driven by passion for excellence tempered by the knowledge all technology is in a temporal state.
94 April 2025 Subscribe for Free...