Avid Technology Pro Tools SYNC HD, Manual, Page: 34 / 166

Pro Tools | SYNC HD Guide 28
About Digital Clock
AES/EBU
The SYNC HD AES/EBU In connector
only recognizes and uses the clock portion of an in-
coming AES/EBU audio signal. All audio infor-
mation will be ignored and will not be passed to the
SYNC HD AES/EBU Out connector.
Word Clock
Word Clock is a digital clock refer-
ence signal that runs at 1x sample rate (44.1, 48,
88.2, 96, 176.4, or 192 kHz). Avid HD audio inter-
faces have dedicated BNC-style Word Clock con-
nectors. A wide variety of professional audio de-
vices have Word Clock connectors, including
digital mixing consoles, DASH-standard digital
multitrack tape recorders and MDMs (modular
digital multitrack recorders).
Avid HD audio interfaces are always connected
using Loop Sync (see “Clock for Avid HD Audio
Interfaces and Video Peripherals” on page 5 for
more information).
LTC and Clock Reference
LTC can provide both positional and clock infor-
mation in the same timecode signal. LTC can be re-
corded onto and played back from an analog track,
or a VTR audio, address or cue track. LTC cannot
be read when the reference deck is stopped, or
playing back at slow or fast wind speeds (roughly
10x playback speed). Pro Tools will not lock until
the LTC signal is close to playback speed.
While resolving to LTC as clock reference, the
SYNC HD provides five options to optimize your
system for different types of tasks. This lets you
choose between faster response (for when fast
lock-up time is critical), or highest sound quality
(during critical laybacks, for example).
LTC Servo Gain
The Session Setup window provides a submenu for
LTC Clock Reference choices. The five choices
provide different servo gain settings to reduce the
effects of jitter when locking to linear timecode.
In Standalone mode, these settings are also avail-
able from the front panel.
Servo Gain settings include the following:
LTC 0 (fastest)
Allows the quickest resolving to
incoming LTC, but with greater jitter. This is the
default setting, and should be used when fast lock
ups are critical.
LTC 1
Provides an intermediate fast setting.
LTC 2 (average)
Offers a compromise of lock up
time and jitter quality.
LTC 3
Provides an intermediate slow setting.
LTC 4 (smoothest)
Offers the lowest jitter from
LTC resolve, but can take six to ten seconds to
achieve full resolve. This setting is most appropri-
ate when loading audio from an analog master,
where reducing or eliminating jitter is more im-
portant than lock speed. When using this setting,
be sure to allow adequate pre-roll before punching
in.
To resolve SYNC HD to Linear Timecode using
Pro Tools:

In the
Sync Setup
section of the Session Setup
window, choose an LTC and Servo Gain setting
from the
Clock Reference
pop-up menu.
To resolve SYNC HD to Linear Timecode using the
front panel controls:
1
Press the Clock Reference switch to select LTC.
2
Set the LTC Servo Gain from the front panel.
See “Servo Gain” on page 48.
For additional digital clock signal informa-
tion, see “Digital Clock Signal Types” on
page 59.