MOTU 896 User's Guide download pdf (Page 21)

INSTALLING THE 896HD HARDWARE

MAKING SYNC CONNECTIONS

If you connect devices digitally to the 896HD, or if

you need to synchronize the 896HD with an

outside time reference such as SMPTE time code,

you must pay careful attention to the synchroni-

zation connections and clock source issues

discussed in the next few sections.

Do you need to synchronize the 896HD?

If you will be using only the 896HD’s analog inputs

and outputs (and none of its digital I/O), and you

have no plans to synchronize your 896HD system

to SMPTE time code or other external clock

source, you don’t need to make any sync

connections. You can skip this section and proceed

to chapter 6, “MOTU FireWire Control Panel (Mac

OS 9)” (page 45) where you’ll open the MOTU

FireWire Audio Console and set the Clock Source

setting to Internal as shown below. For details, see

chapter 6, “MOTU FireWire Control Panel (Mac

OS 9)” (page 45).

Figure 4-5: You can run the 896HD under its own internal clock when

it has no digital audio connections and you are not synchronizing the

896HD system to an external time reference such as SMPTE time

code.

Situations that require synchronization

There are three general cases in which you will

need to resolve the 896HD with other devices:

■ Synchronizing the 896HD with other digital

audio devices so that their digital audio clocks are

phase-locked (as shown in Figure 4-6)

■ Slaving the 896HD system to SMPTE time code

from a video deck, analog multi-track, etc.

■ Both of the above

Synchronization is critical for clean digital I/O

Synchronization is critical in any audio system, but

it is especially important when you are transferring

audio between digital audio devices. Yo u r s u ccess

in using the 896HD’s digital I/O features depends

almost entirely on proper synchronization. The

following sections guide you through several

recommended scenarios.

Be sure to choose a digital audio clock master

When you transfer digital audio between two

devices, their audio clocks must be in phase with

one another — or phase-locked. Otherwise, you’ll

hear clicks, pops, and distortion in the audio — or

perhaps no audio at all.

Figure 4-6: When transferring audio, two devices must have phase-

locked audio clocks to prevent clicks, pops or other artifacts.

There are two ways to achieve phase lock: slave one

device to the other, or slave both devices to a third

master clock. If you have three or more digital

audio devices, you need to slave them all to a single

master audio clock.

Figure 4-7: To keep the 896HD phased-locked with other digital audio

devices connected to it, choose a clock master.

Also remember that audio phase lock can be

achieved independently of time code (location).

For example, one device can be the time code

master while another is the audio clock master. But

only one device can be the audio clock master. If

you set things up with this rule in mind, you’ll have

trouble-free audio transfers with the 896HD.

Not phase-locked Phase-locked

Device A

Device B

Master

Slave

Master

Slave Slave

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MOTU 896 User's Guide Page 21

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