Avid Technology HD I User manual

HD I/O Guide
Version 8.1

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Contents iii
contents
Chapter 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
HD I/O Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
What’s Included . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
System Requirements and Compatibility Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
About This Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
About www.avid.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Chapter 2. HD I/O Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
HD I/O Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
HD I/O Back Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 3. Connecting HD I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Chapter 4. HD I/O Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Configuring HD I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Using Input Trims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Appendix A. Adding or Removing I/O Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Removing an I/O Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Installing an Expansion I/O Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

HD I/O Guideiv
Appendix B. Pinout Diagrams for the DB-25 Connectors . . . . . . . . . . . . . . . . . . . . . . . 33
Analog Output DB-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Analog Input (+4 dBu) DB-25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Analog Input (–10dBV) DB-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
AES/EBU DB-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
TDIF DB-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix C. HD I/O Calibration Mode Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
About Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Calibrating the HD IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Switching Jumpers on the Analog Output Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Appendix D. Compliance Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Environmental Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
EMC (Electromagnetic Compliance) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Safety Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Chapter 1: Introduction 1
chapter 1
Introduction
HD I/O is a multi-channel digital audio interface
designed for use with Pro Tools|HD®systems.
HD I/O features 24-bit analog-to-digital (A/D)
and digital-to-analog (D/A) converters, and sup-
ports sample rates of up to 192 kHz.
HD I/O comes in three standard configurations:
• 8 x 8 x 8 (8 analog in, 8 analog out, and 8
digital in and out)
• 16 x 16 analog in and out
• 16 x 16 digital in and out
You can also add or remove analog (ADC and
DAC) and digital cards for custom configura-
tions.
HD I/O Features
HD I/O provides up to sixteen discrete channels
of Pro Tools input and output, each with a 4-seg-
ment LED meter. The total available analog and
digital I/O is dependent on the configuration of
Analog and Digital Expansion I/O cards in-
stalled in HD I/O.
Analog I/O
• Up to sixteen channels of 24-bit D/A and A/D
converters for superior analog input and out-
put at sample rates of 44.1 kHz, 48 kHz,
88.2 kHz, 96 kHz, 176.4 kHz, and 192 kHz
with Analog In and Analog Out HD I/O cards
• Soft Clip and Curv limiting circuits to protect
against clipping on analog input.
Digital I/O
• Up to sixteen channels of 24-bit digital I/O,
using AES/EBU, TDIF DB-25, or Optical at
sample rates of 44.1 kHz, 48 kHz, 88.2 kHz, 96
kHz, 176.4 kHz, and 192 kHz with a Digital
HD I/O card
• Real-time sample rate conversion on digital
inputs with a Digital I/O card (up to sixteen
channels of AES/EBU, Optical, or TDIF)
• Support for S/MUX Optical for sample rates of
88.2 kHz and higher
• Support for 2 channels of S/PDIF Optical (en-
closed) with sample rates of up to 96 kHz
• 2 channels of AES/EBU I/O (enclosed) with
support for sample rates up to 192 kHz
• 2 channels of 24-bit-capable S/PDIF I/O (en-
closed) with support for sample rates up to
192 kHz

HD I/O Guide2
Synchronization
• Loop Sync input and output for connecting
additional Pro Tools|HD interfaces and pe-
ripherals
• External Clock input and output for synchro-
nizing HD I/O with external Word Clock de-
vices
Expandability
• Optional addition of I/O cards to expand ana-
log or digital I/O
• Simultaneous use of multiple Pro Tools|HD
audio interfaces to further expand system in-
put and output (for more information see the
Expanded Systems Guide)
What’s Included
• HD I/O audio interface
•ACpowercable
• DigiLink Mini cable (18 inches [0.46m])
• DigiLink to DigiLink Mini adapter cable
• BNC cable (18 inches [0.46m])
• HD I/O Guide
• Health and Safety Guide
• Registration Information Card
System Requirements and
Compatibility Information
HD I/O requires a qualified Pro Tools|HD
system.
Avid can only assure compatibility and provide
support for hardware and software it has tested
and approved.
For complete system requirements and a list of
qualified computers, operating systems, hard
drives, and third-party devices, visit:
www.avid.com/compatibility
Registration
Review the enclosed Registration Information
Card and follow the instructions on it to quickly
register your purchase online. By registering,
you become eligible to receive the following:
• Information regarding technical support
• Software update and upgrade notices
• Limited warranty on hardware
About This Guide
This guide provides a basic overview of the
HD I/O features and functionality.
For complete instructions on connecting and
configuring your Pro Tools|HD system, see the
Pro Tools|HD User Guide.
For additional information about using
Pro Tools software, see the Pro Tools Reference
Guide (in Pro Tools, choose Help > Pro Tools
Reference Guide).

Chapter 1: Introduction 3
Conventions Used in This Guide
All of our guides use the following conventions
to indicate menu choices and key commands:
:
The names of Commands, Options, and Settings
that appear on-screen are in a different font.
The following symbols are used to highlight
important information:
About www.avid.com
The Avid website (www.avid.com) is your best
online source for information to help you get
the most out of your Pro Tools system. The fol-
lowing are just a few of the services and features
available.
Product Registration Register your purchase on-
line.
Support and Downloads Contact Avid Customer
Success (technical support); download software
updates and the latest online manuals; browse
the Compatibility documents for system re-
quirements; search the online Knowledge Base
or join the worldwide Pro Tools community on
the User Conference.
Training and Education Study on your own using
courses available online or find out how you can
learn in a classroom setting at a certified
Pro Tools training center.
Products and Developers Learn about Avid prod-
ucts; download demo software or learn about
our Development Partners and their plug-ins,
applications, and hardware.
News and Events Get the latest news from Avid
or sign up for a Pro Tools demo.
Convention Action
File > Save Choose Save from the
File menu
Control+N Hold down the Control key
and press the N key
Control-click Hold down the Control key
and click the mouse button
Right-click Click with the right
mouse button
User Tips are helpful hints for getting the
most from your system.
Important Notices include information that
could affect your data or the performance of
your system.
Shortcuts show you useful keyboard or
mouse shortcuts.
Cross References point to related sections in
this guide and other Pro Tools guides.

HD I/O Guide4

Chapter 2: HD I/O Overview 5
chapter 2
HD I/O Overview
This chapter describes the front and back panel features of the HD I/O.
HD I/O Front Panel
Power Switch and LED Ring
This button turns the HD I/O on and off.
The LED ring around the power button will light
green to indicate that the unit has powered up
successfully and is connected to an active
Pro Tools|HD system. If the LED ring is orange,
the unit has power, but the computer it is con-
nected to is shut down.
Sample Rate
These LEDs display the current sample rate of
the HD I/O internal clock: 44.1 kHz, 48 kHz,
88.2 kHz, 96 kHz, 176.4 kHz, or 192 kHz. The
sample rate can be set in Pro Tools when you
create a new session, or in the Hardware Setup or
Playback Engine dialogs if no session is open.
See the Pro Tools|HD User Guide for complete system installation and configuration instructions. If you
are adding the HD I/O to an existing system, see the Expanded Systems Guide.
HD I/O Front Panel

HD I/O Guide6
Loop Master LED
The LOOP MASTER LED indicates which
Pro Tools audio interface is the master Pro Tools
peripheral. The Loop Master LED will be contin-
uously lit on the current Loop Master peripheral
only, and unlit on all other peripherals. (Only
one Pro Tools audio interface can be Loop Mas-
ter at a time.) The Loop Master LED will always
be lit with a single interface.
For Pro Tools|HD systems, Loop Master defaults
to the first Pro Tools audio interface connected
to the Pro Tools|HD Core card.
Sync Mode LEDs
The SYNC MODE LEDs indicate the current
Clock Source as set in Pro Tools.
INT (Internal) Indicates the HD I/O sample clock
is generated by its internal clock, as determined
by the session Sample Rate.
DIG (Digital) Indicates that an external AES/EBU,
TDIF, Optical (ADAT), Optical (ADAT S/MUX),
or S/PDIF device is providing system clock. If no
valid clock source is detected, HD I/O will
switch to internal clock, the DIG LED will flash,
and an error message will appear on-screen in
Pro Tools.
LOOP Indicates that the HD I/O is slaving to an-
other Pro Tools|HD audio interface using Loop
Sync.
EXT (External) Indicates that the HD I/O is using
the EXT CLOCK IN port for system synchroniza-
tion.
When synchronized to Word Clock, External
Clock input and output do not have to be at the
Word Clock rate. EXT CLOCK IN synchroniza-
tion will typically be 1x the current session sam-
ple rate. However, for sample rates higher than
48 kHz, HD I/O generates a choice of 1x, 2x, or
4x of a base rate of 44.1 kHz or 48 kHz, as
follows:
Meters
These four-segment LEDs indicate signal level
for each of the sixteen channels. The top row
of meters indicates input levels, and the bottom
row shows output levels. These meters are
calibrated at –42 dB, –18 dB, –6 dB, and 0 dB,
respectively.
Session Sample Rate Word Clock Support
44.1 kHz 44.1 kHz
48 kHz 48 kHz
88.2 kHz 88.2 kHz
44.1 kHz
96 kHz 96 kHz
48 kHz
176.4 kHz 176.4 kHz
44.1 kHz
192 kHz 192 kHz
48 kHz
Note that 0 dB is not to be confused with
clipping; use the on-screen meters in
Pro Tools to determine whether a signal is
clipping.

Chapter 2: HD I/O Overview 7
HD I/O Back Panel
The HD I/O has the following back panel features:
Although the HD I/O is a sixteen-channel audio
interface, it has up to 94 inputs and outputs
available through its various back panel connec-
tors.
HD I/O comes in three standard configurations:
• 8 x 8 x 8 analog and digital in and out
• 16 x 16 analog in and out
• 16 x 16 digital in and out
Input and Output Cards
The HD I/O features four bays for HD I/O Expan-
sion cards. With the standard 8 x 8 x 8 configu-
ration, bays 1–3 contain Analog In, Analog Out,
and Digital I/O cards, respectively. The fourth
bay (as shown in this 8 x 8 x 8 configuration) is
an expansion bay, for which you can purchase
an additional Expansion I/O card of your
choice.
By installing an optional AD Expansion card,
DA Expansion card, or Digital Expansion card,
you can add even more I/O capacity (up to a
maximum possible 110 inputs and outputs). See
Appendix A, “Adding or Removing I/O Cards.”
HD I/O Back Panel, 8 x 8 x 8 configuration shown
964530300294856
WORD CLOCK LOOP SYNC
PRIMARY PORT
EXPANSION PORT
IN
OUT
AC ~ 100-240V;50-60HZ; A
S/PDIF
IN
OUT
AES/EBU
INPUT
AES/EBU
OUTPUT
OPTICAL
IN OUT
ACCESSORY
12345678
ANALOG INPUT
+4 dBu BALANCED -10 dBV BALANCED
12345678
ANALOG OUTPUT
BALANCED
DIGITAL I/O
AES/EBU
ADAT
IN
TDIF I/O
ADAT
OUT
Bay 2: Analog Out card
Bay 1: Analog In card Bay 3: Digital I/O card
Bay 4: Empty for Optional card
Enclosure
Input and Output cards for 192 I/O are not
supported in HD I/O.

HD I/O Guide8
Analog Input
The HD I/O Analog In card contains connectors
for analog audio input with 24-bit, 192 kHz A/D
converters. Input is provided through two dis-
crete DB–25 connectors (one for +4 dBu sources,
and the other for –10 dBV sources). You can
connect sources at both operating levels and
choose between them from within Pro Tools.
+4 dBu Balanced Provides eight balanced input
channels at +4 dBu nominal operating levels.
–10 dBV Balanced Provides eight balanced input
channels at –10 dBV nominal operating levels.
For wiring information, see Appendix B, “Pin-
out Diagrams for the DB-25 Connectors.”
For each channel, you can select input level
from within the Hardware Setup dialog (see
“Hardware Setup” on page 17).
Input Trims
The Input Trims below the DB–25 connectors
are used to individually calibrate each channel’s
input level. See “Input Trims” on page 26.
Additionally, the Limiter function helps avoid
digital clipping (see“Limiter” on page 22).
Analog Output
The HD I/O Analog Out card contains a single
DB–25 connector and Output Trims for eight
channels of analog audio output. These bal-
anced outputs operate at +4 dBu levels. See
Appendix B, “Pinout Diagrams for the DB-25
Connectors.”
Output Trims
The Output Trims below the DB–25 connector
are used to individually calibrate each channel’s
output level. For more information, see
Appendix C, “HD I/O Calibration Mode Instruc-
tions.”
Most consumer electronics operate at –10 dBV
levels, and may not feature balanced inputs
and outputs. You can connect –10 dBV
signals to the –10 dBV inputs, but you will
need to make sure that the negative terminals
are not connected.
For –10 dBV gear, you can switch a jumper
on Analog Output cards (on a channel-by-
channel basis) from the default Hi position
to Lo for a –6 dB pad. You can then adjust
the Trim pot for the corresponding output
channels by an additional –4 dB to accom-
modate –10 dBV gear. For more information,
see Appendix C, “HD I/O Calibration Mode
Instructions.”

Chapter 2: HD I/O Overview 9
Digital I/O
The Digital I/O card contains connectors for
eight channels each of AES/EBU I/O, TDIF I/O,
and Optical (ADAT) I/O. Only one digital format
can be used at a time.
AES/EBU DB–25 connectors for eight channels
of AES/EBU input and output. Each of the paired
channels is a balanced three-conductor signal,
and supports 192 kHz sample rates in single-
wire mode up to eight channels. Dual-wire
mode uses two HD I/O physical I/O channels of
AES/EBU I/O to carry each single stream of
176.4 kHz or 192 kHz audio. Therefore, only
four simultaneous channels of AES/EBU I/O are
available at 176.4 kHz or 192 kHz.
TDIF DB–25 connectors for eight channels of
TDIF input and output. Conforms to standard
eight-channel TDIF pinouts. For more informa-
tion, see Appendix B, “Pinout Diagrams for the
DB-25 Connectors.”
Optical (ADAT) Dedicated, eight-channel 24-bit
capable Optical ports (up to 48 kHz), with real-
time sample rate conversion on input (only).
Note that Optical S/PDIF is not supported with
the Digital I/O card and is supported with the
enclosed Optical ports only (for more informa-
tion, see “Optical (ADAT) [Encl]” on page 10).
The inputs on the Digital I/O card feature real-
time sample rate conversion. For example, you
can stream audio with a sample rate of 44.1 kHz
into a 96 kHz session.
Enclosure Connectors
The right half of the back panel of HD I/O fea-
tures a set of non-removable connectors that are
mounted to the enclosure.
These connectors include two channels of
AES/EBU IO, Optical I/O (for another eight
channels of ADAT format, or two channels of
Optical S/PDIF), and two channels of coaxial
S/PDIF I/O. On-screen, these connectors are
identified as AES/EBU [Encl], Optical (ADAT)
[Encl], Optical (S/PDIF) [Encl], and S/PDIF
[Encl].
Other connectors include Loop Sync, External
Clock, and ports for attaching the HD I/O to
Pro Tools|HD cards or to other Pro Tools|HD au-
dio interfaces.
We recommend using Avid DB-25 TDIF ca-
bles for optimum compatibility.
For more information, see“Hardware Setup”
on page 17.

HD I/O Guide10
AES/EBU [Encl]
These are balanced, three-conductor XLR con-
nectors that accept and output a stereo, 24-bit
AES/EBU audio signal. These two ports support
up to 192 kHz sample rates.
S/PDIF Digital In and Out
These are unbalanced RCA jacks that receive and
send two channels of S/PDIF audio. S/PDIF sup-
ports up to 24-bit audio, at sample rates up to
192 kHz.
Optical (ADAT) [Encl]
These Optical ports provide up to eight channels
of Optical (ADAT) input and output, or two
channels (stereo) optical S/PDIF input and out-
put. Optical (ADAT) mode supports sample rates
up to 48 kHz. Using S/MUX, these Optical ports
support provide up to four channels of Optical
S/MUX input and output at sample rates of 88.2
and 96 kHz, and up to two channels of Optical
S/MUX input and output at sample rates of
176.4 and 192 kHz. In TOS-Link mode, the ports
support two channels of Optical input and out-
put at sample rates up to 96 kHz.
About Lightpipe-Compatible Devices
Lightpipe is an industry standard, eight-channel
optical digital audio connection created by Ale-
sis. Lightpipe is found on many devices, includ-
ing Optical (ADAT) decks, modular digital mul-
titracks (MDMs), A/D or D/A converters,
S/MUX, and digital consoles.
DigiLink Mini Ports
PRIMARY PORT
Use the PRIMARY PORT to connect HD I/O to
your Pro Tools|HD system using a DigiLink Mini
to DigiLink cable (adapter included).
The Primary port sends and receives 32 channels
to and from a Pro Tools|HD card. Input and out-
put channels 17–32 (if active) are passed
through to the EXPANSION PORT.
EXPANSION PORT
The EXPANSION PORT lets you connect an ad-
ditional Pro Tools|HD audio interface to
HD I/O. The EXPANSION PORT passes input
and output channels 17–32 to the expansion (or
secondary) audio interface.
This port is only available when HD I/O is con-
nected to a Pro Tools|HD card (it is not available
when the HD I/O is connected to the Expansion
Port on another audio interface).
To maintain data integrity and minimize
jitter, use only 75-ohm coaxial cable for
S/PDIF connections.
Configure HD I/O for ADAT S/MUX on the
enclosed ADAT port and also on the ADAT
port on the Digital I/O card to get 8 chan-
nels at 88.2/96 kHz or 4 channels at
176.4/192 kHz.

Chapter 2: HD I/O Overview 11
DigiLink Mini and DigiLink Cables
Use DigiLink cables with a DigiLink to DigiLink
Mini adapter cable to connect HD I/O to a
Pro Tools|HD card, as well as to legacy
Pro Tools|HD audio interfaces (such as 192 I/O).
Use DigiLink Mini cables to connect HD I/O to
other Pro Tools|HD audio interfaces (such as an-
other HD I/O or HD OMNI).
DigiLink Mini Cable Length Specifications
There are six different lengths of DigiLink Mini
cables:
•18”(0.46m), included with HD I/O
•12’(3.6m) (sold separately)
•25’(7.62m) (sold separately)
•50’(15.25m), the maximum length sup-
ported for 176.4 kHz and 192 kHz sessions
(sold separately)
• 100’ (30.5m), the maximum length sup-
ported by 88.2 kHz and 96 kHz sessions
(sold separately)
• 200’ (30.5m), the maximum length sup-
ported by 44.1 kHz and 48 kHz sessions
(sold separately)
DigiLink to DigiLink Mini Adapter Cables
Use DigiLink to DigiLink Mini adapter cables to
connect HD I/O to Pro Tools|HD cards. You can
also use DigiLink to DigiLink Mini adapter ca-
bles to connect older HD peripherals (such as
192 I/O) to the Expansion port of HD I/O.
There are two types of DigiLink to DigiLink Mini
adapter cables:
•12”DigiLink female to DigiLink Mini male,
included with each interface
• 12” DigiLink Mini female to DigiLink male
The DigiLink to DigiLink Mini adapter cables let
you connect your HD I/O to Pro Tools|HD cards
in your computer (Pro Tools|HD cards include a
12’ DigiLink cable for connecting Pro Tools|HD
audio interfaces). They also let you connect leg-
acy Pro Tools|HD audio interfaces (such as the
192 I/O or the 96 I/O) to the expansion port of
HD I/O (legacy Pro Tools|HD audio interfaces
include an 18” DigiLink cable).
Clock and Synchronization Ports
WD CLOCK IN and OUT
The Word Clock I/O ports are standard BNC
connectors that receive and output word clock
signal. These ports can be used to synchronize
HD I/O with any word clock-capable device.
Word Clock In can be configured by selecting it
as the Clock Source in the Hardware Setup dia-
log in Pro Tools. Word Clock Out can also be
configured in the Hardware Setup dialog using
the External Clock Output selector.
For more information about DigiLink Mini
and DigiLink Mini to DigiLink cables, visit
the Avid website (www.avid.com).
Because crucial timing data is passed
through the Loop Sync and Word Clock ports,
you should use high-quality, 75-ohm RG–59
cables for making connections.

HD I/O Guide12
LOOP SYNC In and Out
Loop Sync is a dedicated clock loop for synchro-
nizing multiple Pro Tools|HD peripherals to-
gether (multiple audio interfaces, or a SYNC HD
and one or more audio interfaces). Loop Sync
technology lets you synchronize to any digital
peripheral connected to any of the Pro Tools|HD
audio interfaces in your Pro Tools system. Loop
Sync uses a word clock signal based on sample
rates of either 44.1 kHz or 48 kHz. As sample
rate increases in the system, Loop Sync contin-
ues to operate at a base rate of 44.1 kHz or
48 kHz, depending upon the higher rate.
The Loop Sync In and Out ports are standard
BNC connectors that output a 1x Word clock
signal. Loop Sync should only be used to chain
multiple Pro Tools|HD peripherals together
(such as Pro Tools|HD audio interfaces and
SYNC HD).
AC Power
This connector accepts a standard AC power ca-
ble. HD I/O is auto power-selecting (100V to
240V) and will automatically work with a stan-
dard modular cable (IEC) to connect to AC
power outlets in any country.
Accessory Port
This port currently has no functionality.

Chapter 3: Connecting HD I/O 13
chapter 3
Connecting HD I/O
You can get a full sixteen channels of analog
and digital I/O with HD I/O connected to a
Pro Tools|HD card using a DigiLink Mini to
DigiLink cable.
You can add additional Pro Tools|HD audio in-
terfaces to your Pro Tools|HD system using the
Expansion port on the back of HD I/O or using
additional Pro Tools|HD cards.
To connect HD I/O to a Pro Tools|HD system:
Connect HD I/O Primary Port to the DigiLink
Port on the first available Pro Tools|HD card
with a DigiLink Mini to DigiLink cable (in-
cluded with your Pro Tools|HD system).
For more information about installing
Pro Tools|HD cards, see the Pro Tools|HD
User Guide.
Pro Tools|HD audio interfaces need room at
their sides to maintain proper air flow for
cooling. Do not block the sides of the unit or
disconnect the internal fan. If the units are
rack-mounted in a case, remove the case
lids or doors before operating the system.
Failure to do so can result in the units over-
heating very quickly, which can perma-
nently damage sensitive components.
Figure 1. HD I/O connected to the DigiLink Port on a Pro Tools|HD Core card (16-channel I/O system)
12-foot DigiLink Mini
Pro Tools|HD Core card
to DigiLink cable, or a
12-foot DigiLink cable
with a DigiLink to
DigiLink Mini adapter

HD I/O Guide14
To connect multiple HD I/Os to a Pro Tools|HD
system:
1 Connect the Primary Port of the first HD I/O
to the DigiLink Port on the Pro Tools|HD Core
card with a DigiLink Mini to DigiLink cable (in-
cluded with your Pro Tools|HD system).
2 Do one of the following:
• Connect the Primary Port of the second HD
I/O to the Expansion Port on the first HD
I/O with the included 18-inch DigiLink
Mini cable.
– or –
• Connect the Primary Port of the second HD
I/O to the next available Pro Tools|HD card
with a DigiLink Mini to DigiLink cable (in-
cluded with your Pro Tools|HD system).
3 Connect additional HD I/Os to additional
Pro Tools|HD cards.
4 Make the necessary Loop Sync connections.
Connecting Loop Sync
If you are using two (or more) Pro Tools audio
interfaces or a SYNC peripheral, Loop Sync must
be connected to maintain proper clock among
the devices. For an example of connecting mul-
tiple Pro Tools|HD audio interfaces, see Figure 2
below.
To make Loop Sync connections:
1 Connect (daisy-chain) the Loop Sync Out of
each interface to the Loop Sync In of the next
interface with the BNC cables included with
your audio interface.
2 Connect the Loop Sync Out of the last inter-
face to the Loop Sync In of the primary interface
or SYNC peripheral.

Chapter 3: Connecting HD I/O 15
Figure 2. HD OMNI connected to the DigiLink Port on a Pro Tools|HD Core card and HD I/O connected to the DigiLink
Mini Expansion port on HD OMNI. A second HD I/O is connected to the DigiLink Port on a Pro Tools|HD Accel card
with a third HD I/O connected to the Expansion port on the second HD I/O. Loop Sync (BNC) cables connect the HD
OMNI and all three HD I/Os.
12-foot DigiLink Mini Pro Tools|HD Core card
to DigiLink cable
Pro Tools|HD Accel card
Loop Sync cables
18-inch DigiLink
Mini cable

HD I/O Guide16