Digital Clock - Alesis AI-3 Reference Manual

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Where the previous chapters explained the various connectors and switches on the
AI-3, this chapter describes how to connect it to the components in your studio. Since
the AI-3 doesn't do much on it's own, this chapter will help you get the most out of
this interface.

Digital Clock

The most important concept to understand in a studio using several digital
connectors is the digital clock. It's critical that every unit being connected with a
digital connector like an ADAT Optical cable is running at the same clock speed.
Digital audio signals like the ADAT Optical format are made up of digital sample
words. Each word is a burst of numbers: a 20-bit, 48kHz signal is made up of a word
20 bits long, played 48,000 times every second. If the sending unit and the receiving
unit aren't in perfect sync then the signal will be distorted. For example, if an ADAT
was running at 48,000 samples per second (48kHz), and your digital mixer was
running at 48,001 samples per second, you would hear a "click" when the samples
didn't exactly line up.
The way to fix this is to set every unit in your studio to run from the same master
clock. Whether it's an ADAT, computer-based editing workstation, digital mixer or
DAT machine, you need to pick one unit in your studio which is the master clock,
and every other digitally-connected unit needs to slave to this master.
How does this affect the AI-3? The easiest way to use an AI-3 in a digital studio is to
make sure that the digital input is always connected. When digital clock is coming
into the AI-3's digital input, it automatically slaves to this clock source. If you only
connect the digital output of the AI-3 to another product, such as a mixer or recorder,
then the AI-3 has to be the master clock.
The next few pages illustrate a few example setups using the AI-3. Use these
configurations as a guide when setting up the AI-3 in your studio.
AI-3 Reference Manual
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PPLICATIONS
Applications – Chapter 3
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