A Common Clock
It should be noted that all digital network components should be synched to a common clock.
The best way to achieve this is with the use of a separate word clock.
This will allow all devices in the chain to be locked to each other and thus eliminate any phase shifts that may occur between devices from un-synched sampling rates.
With advances in digital technology, latencies for audio gear have dropped dramatically, to the point that some digital mixers are below 3 ms for analog in to analog out with no added time for DSP.
The problem lies in cascading multiple digital devices together if not digitally linked. When having to make A/D and D/A conversions for every piece of digital gear in a signal chain, it’s easy to see how the latencies from conversion alone can add up to an unacceptable total.
Two key factors in comparing digital audio networks are the sampling rate and the bit resolution that the network supports.
The sampling rate is the ”rate” at which a digital device ”samples” the composite analog sound waveform over time.
The sampling rate is important for the way digital audio can describe the frequencies in a sound.
Bit depth, or resolution, describes the potential accuracy of a particular piece of hardware or software that processes audio data. In general, the more bits that are available, the more accurate the resulting output from the data being processed.
For example, audio recorded with a 48 kHz sampling rate and 24 bits of resolution will have 48,000 measurements of which there are 16.7 million different values that each measurement can be per second.
Sampling rates and bit resolutions are important to digital audio networks because they need to remain consistent to keep the latency to a minimum.
A sampling rate conversion typically takes the same amount of time as an A/D conversion.
The major limitation on the number of channels a network can support is bandwidth, which is the amount of information that can be sent down the chain at one time.
The bandwidth required to pass one channel of audio varies with the sampling rate and the bit depth selected. As both increase, so too does the bandwidth demand reducing the maximum number of channels which can be transported over a particular network’s architecture.
Well, what if you could have just one A/D conversion at the start of the signal chain and one D/A at the end with all the other gear still in the chain?
Now we’re talking about the digital audio networks. Again, there are two groups of these digital audio networks, so let’s take a closer look at both.