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INSTALLING THE 896MK3 HARDWARE
31
Sample rate conversion
With sample rate conversion (SRC), an extra level
of master/slave clocking is added to the equation,
as demonstrated below in Figure 4-13, which
shows the clocking going on when you transfer
digital audio from the 896mk3 (AES/EBU OUT) to
a DAT deck (AES/EBU IN) using SRC. Notice that
with SRC, the DAT deck is not slaved to the
896mk3’s system clock. Instead, their clocks are
running completely independently of one another.
But also notice that the DAT deck must still slave to
the sample-rate-converted output from the
896mk3 for a clean digital audio transfer (unless it
has its own sample rate converter on its AES/EBU
input).
Figure 4-13: Clock relationships when sending audio from the
896mk3 to a DAT deck using sample rate conversion. The DAT deck
needs to be slaving to its AES/EBU input. *Note: the 896mk3 AES/EBU
output can actually be clocked from a number of different sources. In
this example, it is resolved to the 896mk3 system clock. For details
about other possible clock sources, see “Clocking scenarios for AES/
EBU output” on page 32.
System clock, AES clock & rate convert settings
When you are setting up AES/EBU input and
output with the 896mk3, pay careful attention to
the following settings in MOTU Audio Console
(see the quick reference overview on page 9):
■ Clock source
■ Sample rate conversion
These options are mentioned briefly in the
following sections. For further details, see “Master
Clock Source” on page 41 and “Sample Rate
Convert” on page 44.
Clocking scenarios for AES/EBU input
There are three possible clocking scenarios for the
896mk3 AES/EBU input:
1. Simple transfer (slave the 896mk3 system clock
to the AES/EBU input signal — no sample rate
conversion).
2. Sample rate convert the AES/EBU input.
3. Use word clock to resolve the 896mk3 system
clock and the other AES/EBU device with each
other.
These three AES/EBU input scenarios are
summarized below.
896mk3 master clock
Input
clock
Output
clock
896mk3
Sample Rate
converter
(slaves to 896mk3 SRC output clock)
(master)
(slaves to 896mk3 master clock)
DAT deck
(master*)
Scenario 1 Scenario 2 Scenario 3
Description
Simple
transfer
Rate
convert
Use word
clock
896mk3 clock
source setting
AES/EBU Any setting
except
AES/EBU
Word Clock
Sample rate
conversion
setting
None AES In None
Required
896mk3 cable
connections
AES/EBU In AES/EBU In AES/EBU In
and Word
Clock In
Are the devices
continuously
resolved?
Yes No Yes
Is the signal
being sample
rate converted?
No Yes No
Example
application
Simple digital
transfer into
the 896mk3
from DAT
deck or digi-
tal mixer.
Transfer from
digital mixer
running at a
different
sample rate.
Both the
896mk3 and
other AES/
EBU device
are slaved to
‘house” word
clock.
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