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6 - Appendix
Word Clock In/Out
76 Creative Professional
Word Clock In/Out
f Word clock and
S/PDIF synchronize at the
sample rate and are used
to transfer digital data
between machines.
Word clock provides a standardized means of synchronizing multiple digital audio
devices so that data can be transferred digitally. In order to digitally transfer from one
device to another, the two devices MUST be synchronized. Clicks and pops in the
audio will result when transferring digital audio which is not synchronized.
The E-MU 0404 PCI card can be externally clocked from the S/PDIF input (either optical
or electrical) or from the Sync Daughter card (if installed). In a digital studio, all
digital devices in the system should run off the same master Word Clock.
To Synchronize PatchMix DSP to an External Clock Source:
1. Make sure an external clock source is connected to the E-MU Digital Audio System
hardware via the word clock or S/PDIF input.
2. Open the Session Settings dialog box.
3. Under the System tab, select External Source, then select either Word Clock or
S/PDIF.
4. Press OK to close the dialog box.
5. Check the Sync section of PatchMix DSP to verify that the Locked indicator is
illuminated.
Devices can be connected in daisy chain fashion (word clock out connected to the next
unit’s word clock in) or in parallel for one or two devices, but professional digital
studios normally use a master word clock generator or “House Sync” with a distribution
system so that each device receives a phase-coherent and jitter-free word clock.
Word Clock In: Receives word clock (sample clock) from another digital device such as
a digital video deck, digital recorder or digital mixer.
Word Clock Out: Sends word clock (sample clock) to another digital recorder. Word
clock is always output, whether it is generated by the internal clock or passed through
from the word clock input.
75Ω On/Off: Termination for the word clock input can be switched on or off in the
Sync Card menu of the PatchMix DSP application. Normally word clock termination
should be left on. If you have problems with a weak word clock signal, try turning termi-
nation off. See Word Clock Termination.
The diagram below shows the proper way to connect and terminate a serial word clock
chain. Using a BNC “T” connector ensures that word clock is precisely in phase for both
devices. The middle device has termination turned Off and the last device in the word
clock chain has termination turned On.
House Sync
Generator
Digital
Device 1
Digital
Device 2
Digital
Device 3
Digital
Device 4
A master word clock generator is preferable for larger digital setups.