DigiDesign 888/24 I/O User manual

Digidesign Inc.
3401-A Hillview Avenue
Palo Alto, CA 94304 USA
tel: 650·842·7900
fax: 650·842·7999
Technical Support (USA)
650·842·6699
650·856·4275
Product Information
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800·333·2137
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1-888-USE-DIGI (873-3444)
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www.digidesign.com
Digidesign FTP Site
ftp.digidesign.com
Digidesign
888|24 I/O Audio Interface
Installation Guide

Copyright
This User’s Guide is copyrighted ©1999 by Digidesign, a
division of Avid Technology, Inc. (hereafter “Digidesign”), with
all rights reserved. Under copyright laws, this manual may not
be duplicated in whole or in part without the written consent of
Digidesign.
DIGIDESIGN, AVID and PRO TOOLS are trademarks or
registered trademarks of Digidesign and/or Avid Technology,
Inc. All other trademarks are the property of their respective
owners.
All features and specifications subject to change without
notice.
PN 932707455-00 REV A 11/99
Communications & Safety Regulation Information
Compliance Statement
The model 888/24 I/O complies with the following standards
regulating interference and EMC:
• FCC Part 15 Class A
• EN55103 – 1, environment E4
• EN55103 – 2, environment E4
• AS/NZS 3548 Class A
• CISPR 22 Class A
Radio and Television Interference
This equipment has been tested and found to comply with the
limits for a Class A digital device, pursuant to Part 15 of the
FCC Rules.
Communications Statement
This equipment has been tested to comply with the limits for a
Class A digital device. Changes or modifications to this product
not authorized by Digidesign, Inc., could void the Certification
and negate your authority to operate the product. This product
was tested for CISPR compliance under conditions that
included the use of peripheral devices and shielded cables and
connectors between system components. Digidesign
recommends the use of shielded cables and connectors
between system components to reduce the possibility of
causing interference to radios, television sets, and other
electronic devices.
Safety Statement
This equipment has been tested to comply with USA and
Canadian safety certification in accordance with the
specifications of UL Standards; UL813 and Canadian CSA
standard; CSA C22.2 No.1-M90. Digidesign Inc., has been
authorized to apply the appropriate UL & CUL mark on its
compliant equipment.
Important Safety Instructions
When using electric or electronic equipment, basic precautions
should always be followed, including the following:
• Read all instructions before using this equipment.
• To avoid the risk of shock, keep this equipment away from
rain water, and other moisture. Do not use this equipment
if it is wet.
• The equipment should only be connected to the correct
rating power supply as indicated on the product.
• Do not attempt to service the equipment. There are no
user-serviceable parts inside. Please refer all servicing to
authorized Digidesign personnel.
• Any attempt to service the equipment will expose you to a
risk of electric shock, and will void the manufacturer’s
warranty.
• The product should be connected only to the correct power
supply as indicated on the product.

Contents iii
contents
Using the 888/24 I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The 888/24 I/O Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Changing Operating Levels of Individual 888/24 I/O Channels . . . . . . . . . . . . . . . . . . . . . . . . 6
Making Signal Connections to the 888/24 I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Using the 888/24 I/O Interface as Stand-Alone Audio Converter . . . . . . . . . . . . . . . . . . . . . . . 8
Changing the Default Sample Rate of the 888/24 I/O in A/D Stand-Alone Mode . . . . . . . . . . . 9
Changing the Default Word Clock Lock Port of the 888/24 I/O in D/A Stand-Alone Mode . . . . 10
Muting the DAC Outputs of the 888/24 I/O in A/D Stand-Alone Mode . . . . . . . . . . . . . . . . . . 11
Appendix A. Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix B. Calibrating the 888/24 I/O (Pro Tools 5.0) . . . . . . . . . . . . . . . . . . . . . . . 15
About Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Calibrating The 888/24 I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Appendix C. Calibrating the 888/24 I/O (Pro Tools 4.x) . . . . . . . . . . . . . . . . . . . . . . . 19
About Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Calibrating The 888/24 I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

888/24 I/O iv

Using the 888/24 I/O 1
Using the 888/24 I/O
The 888/24 I/O
™
is an 8-channel digital au-
dio interface that features 24-bit analog-to-
digital, and 24-bit digital-to-analog con-
verters for superior dynamic range, reduced
noise floor, and the capability to work with
the full 24-bit mixing, editing, processing,
and mastering environment of Pro Tools.
The 888/24 I/O can be used in two ways:
◆
As a 24-bit Audio Interface for Pro Tools
◆
As a stand-alone 24-bit audio converter
This User’s Guide explains the indicators
and connectors on the 888/24 I/O. It also
explains how to use it with a Digidesign
Pro Tools
®
system, or as an independent,
stand-alone 24-bit audio converter in your
studio.
☞ If you own a Pro Tools system, most of the
information in this guide is covered in your
Pro Tools TDM Hardware Installation Guide .
The 888/24 I/O Interface
This section explains each of the connec-
tors and indicators on the front and back
panels of the 888/24 I/O Interface, how
they are used, and offers suggestions for
connecting the 888/24 I/O to your studio.
888/24 I/O Front Panel
The 888/24 I/O has the following front
panel indicators, moving from left to right:
1. Power
This switch applies power to the 888/24.
The “I” position is on. The “O” position is
off.
2. Sync Mode
The Sync Mode LEDs indicate which sam-
ple rate clock reference is currently used by
the analog-to-digital converters (ADCs)
and the digital-to-analog converters
(DACs).
Front panel of the 888/24 I/O

888/24 I/O 2
Internal This is the 888/24 I/O standard set-
ting. In this mode, the 888/24 I/O sample
rate is generated by its internal crystal oscil-
lator (whose frequency is determined by
the Sample Rate setting in the Session
Setup window). Internal mode should be
active whenever the 888/24 I/O is not syn-
chronized to an external clock source.
Digital This setting indicates that an
AES/EBU or S/PDIF word clock signal is cur-
rently the source for the 888/24 I/O sample
rate. This is the setting to use for inputting
material from DAT recorders or other digi-
tal devices.
To use the 888/24 I/O digital inputs and
outputs as effects sends and returns to dig-
ital effects devices, you should set the
888/24 I/O to Internal Sync Mode. You
should then set the digital effects device to
accept an external digital clock (from the
888/24 I/O) so it synchronizes itself to
Pro Tools.
The 888/24 I/O can only synchronize to
and receive word clock lock on channels
1–2 of its digital inputs. To synchronize
your system to an external digital clock
source, it must be connected to digital in-
puts 1–2 of the 888/24 I/O. In an expanded
Pro Tools system, the system clock is car-
ried by the Audio Interface connected to
the first Pro Tools card in your system. This
Audio Interface will act as the master inter-
face in your system. All other Audio Inter-
faces will be slaved to it.
▲ Because some digital audio devices do not
output proper clock when they are not playing
back, leaving the 888/24 I/O in Digital Sync
Mode may cause Pro Tools audio playback
quality to suffer, or play back at the wrong
pitch. If you are using digital I/O, reset the
Sync Mode from Digital to Internal after input-
ting material.
Slave This LED is lit when the 888/24 I/O
sample rate is synchronized to another
Digidesign Audio Interface or synchroniza-
tion peripheral. In this mode, the sample
rate of the slave interface is derived from
the frequency of the incoming master
clock signal present at the Slave Clock
(256x) port.
The 888/24 I/O automatically switches to
this mode when a Slave Clock Out signal
from another Digidesign Interface, Univer-
sal Slave Driver, Video Slave Driver, or
SMPTE Slave Driver is connected to the
888/24 I/O Slave Clock In port.
In expanded Pro Tools systems, the Super
Clock output of the master Audio Interface
locks all other interfaces together with
sample accuracy, keeping all signals phase-
synchronous.
✽ When slaving to a Digidesign Universal
Slave Driver, Video Slave Driver, or SMPTE
Slave Driver, set the clock source to Internal.
The Audio Interface will automatically switch to
Slave mode when it detects the 256x input
clock.

Using the 888/24 I/O 3
3. Sample Rate and 1–2 Format
Indicators
These LEDs indicate the sample rate of the
888/24 I/O internal crystal oscillator and
the digital format (AES/EBU or S/PDIF) of
the audio input signal to channels 1 and 2.
The choice of digital format for these two
channels is made in the Session Setup win-
dow or Hardware Setup dialog. Digital in-
put pairs 3–4, 5–6, and 7–8 of the
888/24 I/O are always AES/EBU. Sample
Rate is set in the Session Setup window or
Hardware dialog in Pro Tools.
The 888/24 I/O provides the following
sample rates:
48 kHz This is a standard sampling rate of
many professional audio devices. It is rec-
ommended for use with devices that can-
not receive digital transfers at 44.1 kHz.
44.1 kHz This is the compact disc standard
sampling rate and the Pro Tools default
sample rate. To avoid the need for sample
rate conversion, you should use this rate
when you are recording material that will
ultimately be published on a compact disc.
▲ When you are using an external digital
source such as a DAT recorder, the front panel
of the 888/24 I/O indicates only the internal
oscillator sample rate, not that of the external
digital source.
4. Level Meters
The 888/24 I/O level meters monitor the
channel outputs of Pro Tools. Input levels
are monitored on-screen in the Pro Tools
software.
The 888/24 I/O is factory calibrated so that
a meter reading of –18 dB corresponds to
the 888/24 I/O nominal operating level
(which can be set to either +4 dBu or
–10 dBV). If you sent the output to an ana-
log device with a VU meter, this would cor-
respond to “0 VU” on the VU meter.
The red LED indicators on the Audio Inter-
face indicate both full-code (highest level
before clipping) and clipping of Pro Tools
output signals. The on-screen meters in
Pro Tools software indicate clipping when
at least three consecutive full-code samples
follow each other.
5. Input Level Trims
The 888/24 I/O analog inputs are factory
calibrated at a –18 dB nominal level, refer-
enced to a full code signal. This means at
the nominal reference input level (either
+4 dBu or –10 dBV), you have 18 dB of
headroom before clipping. The input level
trim pots allow adjustment of the
888/24 I/O input levels to match the oper-
ating level of your external equipment. Ad-
justments can be made with a Phillips
screwdriver.
6. Output Level Trims
The 888/24 I/O analog outputs are factory
calibrated at a –18 dB nominal level, refer-
enced to a full code signal. This means at
the nominal reference output level (either
+4 dBu or –10 dBV), you have 18 dB of
headroom before clipping. The output
level trim pots allow adjustment of the
888/24 I/O output levels to match the op-
erating level of your external equipment.
Adjustments can be made with a Phillips
screwdriver.

888/24 I/O 4
To calibrate the input and output levels of
the 888/24 I/O to match your mixing con-
sole or other devices in your studio, use
Calibration Tool (for Pro Tools 4.3.1 and
earlier) or use Calibration Mode and the
Signal Generator Plug-In (for Pro Tools 5.0
or later).
☞ Instructions for calibrating the 888/24 I/O
appear in Appendix B of this Guide.
888/24 I/O Back Panel
The 888/24 I/O has the following back
panel connectors, moving from left to
right:
1. Analog Audio Outputs
These are balanced male XLR connectors
for analog audio output connections. All
eight output channels are continuously ac-
tive. The 888/24 I/O analog outputs feature
24-bit digital-to-analog converters.
2. Analog Audio Inputs
These are balanced female XLR connectors
for analog audio input connections. The
888/24 I/O analog inputs feature 24-bit an-
alog-to-digital converters. Because input
channels 1–8 of the 888/24 I/O are soft-
ware selectable in pairs between analog or
digital format, analog input to a channel
pair is disabled when digital input format is
chosen for that channel.
The 888/24 I/O analog audio connectors
are balanced XLRs with pin 2 wired hot,
(or “+”); pin 3 cold, (or “–”); and pin 1
ground.
3. AES/EBU Digital Outputs 1–8
The 888/24 I/O AES/EBU output jacks are
balanced, three conductor, XLR connectors
which output a 24-bit digital data stream.
Output is continuously active on both the
AES/EBU and S/PDIF jacks even when the
888/24 I/O input selector is set to analog.
4. AES/EBU Digital Inputs 1–8
The AES/EBU digital format is used in
many professional digital audio devices, in-
cluding some DAT recorders. The Inter-
face’s AES/EBU input jacks are balanced,
three conductor, XLR connectors which ac-
cept a full 24-bit digital data stream.
For AES/EBU connections, 110-ohm cables
are highly recommended for use in profes-
sional installations. For best results, cable
lengths should not exceed 30 meters.
Input channels 1–8 of the 888/24 I/O are
software-selectable in pairs between analog
or digital format. Digital input to a channel
pair is disabled when analog input format
is chosen for that channel in the Hardware
Setup dialog. Input to AES/EBU input chan-
nels 1–2 is disabled when S/PDIF digital for-
mat is chosen for these inputs in the
Pro Tools Session Setup window.
Back panel of the 888/24 I/O

Using the 888/24 I/O 5
5. 50-pin Interface Connector
This 50-pin Computer connector is used to
connect the 888/24 I/O to a MIX card, d24
audio card, Disk I/O card, or a DSP Farm
card. The necessary cable is supplied with
your Audio Interface. If you plan to con-
nect two 888/24 I/O Interfaces to a MIX
card or d24 card, a 16-channel peripheral
cable adapter is necessary. (This cable is
available from your Digidesign dealer.)
6. S/PDIF Digital Input/Output
The Sony Phillips Digital Interface Format
(S/PDIF) is used in many professional and
consumer CD players and DAT recorders.
The 888/24 I/O S/PDIF in/out jacks are un-
balanced 2-conductor phono (RCA) jacks
which utilize a full 24-bit digital data
stream. To avoid RF interference, use 75-
ohm coaxial cable for S/PDIF transfers and
keep the cable length to a maximum of 10
meters.
Because input channels 1–2 of the
888/24 I/O are software selectable between
analog or digital format, input to these two
digital channels is disabled when analog
input is chosen or when AES/EBU digital
format is chosen in the Pro Tools Session
Setup window. Output is continuously ac-
tive on both the AES/EBU and S/PDIF out-
put jacks, regardless of which digital input
format is selected for channels 1–2. To
avoid RF interference, use 75-ohm coaxial
cable for S/PDIF transfers and do not ex-
ceed a cable length of 10 meters.
7/9. Slave Clock In/Out
The Slave Clock Out jack is a standard BNC
type connector that outputs a 256 times
sample rate Super Clock signal for slaving
and synchronizing multiple Digidesign In-
terfaces and synchronization peripherals
together.
When the 888/24 I/O Sync Mode is set to
Internal, connecting a valid Slave Clock
Out signal to this port will cause the
888/24 I/O to automatically switch to Slave
mode. When the 888/24 I/O is the master
interface or the first interface in a chain,
Digital sync mode overrides the Slave
Clock input, and an incoming Slave Clock
Out signal will not switch the 888/24 I/O
to Slave mode.
Because crucial timing data is passed over
these ports, you should use high-quality,
75-ohm RG-59 cables for making connec-
tions, and keep total cable length to less
than 3 meters between interfaces.
8. Power Input
This connector accepts a standard AC
power cable. The Interface is auto power-
selecting (100V to 240V) and will automat-
ically work with a standard modular cable
to connect to AC power receptacles in any
country.

888/24 I/O 6
Changing Operating Levels
of Individual 888/24 I/O
Channels
The 888/24 I/O is factory set to +4 dBu op-
erating levels for input and output. How-
ever, the 888/24 I/O allows you to individ-
ually switch any of its analog inputs or
outputs to either a +4 dBu or –10 dBV oper-
ating level by moving internal jumpers on
its circuit board.
To change the operating level of an input
channel:
1 Turn off your computer and the
888/24 I/O.
2 With a Phillips screwdriver, remove the
screws from the top of the 888/24 I/O.
3 Using the 1/16-inch hex wrench in-
cluded with the 888/24 I/O, carefully re-
move the front four panel screws as noted
on the bag containing the hex wrench.
4 Lift the top off of the 888/24 I/O.
5 Inside the 888/24 I/O chassis, next to
each of the channel input trims, there is a
jumper switch with a removable cap. Lo-
cate the jumper switch for the channel you
wish to modify. Gently lift the cap off the
3-pronged connector. Place it in the posi-
tion corresponding to the operating level
that you desire. For +4 dBu levels, it should
be placed over the rear two prongs. For
–10 dBV levels, it should be placed over the
front two prongs.
6 After you have made the desired changes,
replace the top of the 888/24 I/O.
7 Replace the four front panel screws using
the hex wrench.
8 Replace the top screws with a Phillips
screwdriver.
To change the operating level of an output
channel:
1 Turn off your computer and the
888/24 I/O.
2 Using the 1/16-inch hex wrench in-
cluded with the 888/24 I/O, carefully re-
move the front four panel screws as noted
on the bag containing the hex wrench.
3 With a Phillips screwdriver, remove the
screws from the top of the 888/24 I/O and
lift the top off of the 888/24 I/O.
4 To find the channel output switches, de-
tach the front part of the ribbon cable at
the right side of the chassis. To do this, grip
both sides of the black connector and gen-
tly pull up.
The location of input and output level switches inside
the 888/24 I/O
output level
adjustment switches
+4 dBu or -10 dBV
input level
adjustment switches
+4 dBu or -10 dBV
Setting the input level jumper switches
pull off jumper
place jumper
in this position
to set input
to +4 dBu level
place jumper
in this position
to set input
to -10 dBV level
+4
-10
+4
-10
+4
-10

Using the 888/24 I/O 7
5 With the ribbon cable out of the way
you’ll see eight 3-pronged jumper switches,
each with a removable cap. Locate the
switch for the channel you wish to modify.
6 Gently lift the cap off of the jumper
switch. Place it in the position correspond-
ing to the operating level that you desire.
For +4 dBu levels, it should be placed over
the left two prongs. For –10 dBV levels, it
should be placed over the right two prongs.
7 After you have made the desired changes,
reconnect the ribbon cable and put the top
back on the 888/24 I/O.
8 Replace the four front panel screws using
the hex wrench.
9 Replace the top screws with a Phillips
screwdriver.
Making Signal Connections
to the 888/24 I/O
Depending on how you plan to use the
888/24 I/O, the way you connect it to your
studio will vary.
Choosing between +4 dBu and
–10 dBV operation modes
The 888/24 I/O can be set to operate at
+4 dBu or –10 dBV input and output levels.
It is important that you determine which
line level mode is appropriate for your stu-
dio. In +4 dBu operating mode, the
888/24 I/O is a 24-bit digital audio device
capable of producing audio signals at or
near +26 dBu.
Check the owner’s manual for your mixer,
power amplifier or effects processor to see if
it can handle this load. If it cannot, con-
sider setting the 888/24 I/O to operate at
–10 dBV line levels.
Consider the following when connecting a
mixer:
◆ If your mixer cannot handle more than
1.5V (RMS) inputs at +4 dBu, then you
should set the 888/24 I/O to run at –10 dBV
line level.
◆
If your mixer can handle up to 8.5V
(RMS) inputs, or has pads or attenuators on
its inputs, then you can use the +4 dBu set-
ting on the 888/24 I/O.
Most manuals contain device input specifi-
cations, including whether or not there are
pads or attenuators. Consult the manufac-
turer of your mixer or power amplifier for
further information.
Setting the output level jumper switches
detach
ribbon cable
remove jumper
+4
-10
place jumper
in this position
to set output
to +4 dBu level
place jumper
in this position
to set output
to -10 dBV level

888/24 I/O 8
Setting Up Your Studio
The following diagram illustrates a typical
studio setup, with the 888/24 I/O con-
nected to a mixing console, effects and
other equipment.
The 888/24 I/O analog audio connectors
are balanced XLRs with pin 2 wired hot
(or “+”), pin 3 cold (or “–”), and pin 1
ground.
If you are connecting a balanced system,
pin 1 and shield should be connected at
the input only (not at the output). This will
prevent ground loops between the shield
and pin 1 conductor.
If you are connecting an unbalanced signal
to the 888/24 I/O inputs or outputs, con-
nect only pin 2 to the “+” signal, and pins
1 and 3 to ground at all inputs only.
Using the 888/24 I/O
Interface as Stand-Alone
Audio Converter
The 888/24 I/O can be used apart from
Pro Tools as a stand-alone 8-channel, 24-
bit, analog-to-digital or digital-to-analog
converter.
Before you use the 888/24 I/O in stand-
alone mode:
1 Turn off the 888/24 I/O.
2 Do not turn on your computer while the
888/24 I/O is in stand-alone mode. If you
do, the 888/24 I/O will stop functioning in
stand-alone mode.
To use the 888/24 I/O as a stand alone A/D
converter:
1 Turn off any digital devices that may
send a word clock signal to the 888/24 I/O
channel 1–2 digital input ports.
2 Turn on the 888/24 I/O. The 888/24 I/O
searches briefly for a word clock signal on
channels 1–2 of its digital input ports.
3 If the 888/24 I/O does not detect word
clock, it functions as a stand-alone A/D
converter using its internal clock. In this
mode you will use analog inputs 1–8 and
AES/EBU outputs 1–8.
✽
The default sample rate of the 888/24 I/O
in stand alone A/D mode is 44.1 kHz.To
change this default setting to 48 kHz, you
must open the 888/24 I/O and manually re-
set it by moving an internal jumper switch. See
“Changing the Default Sample Rate of the
888/24 I/O in A/D Stand-Alone Mode” on
page 9.
A typical studio configuration
Power Amp
and Speakers
Digital Inputs/Outputs
Channel 1-2
To DAT Recorder
Digital Inputs/Outputs
Channel 3-4
To Digital Effects Devices
DAT Recorder
Instruments
Connected to Console
Analog
Audio
Inputs 5-8
Analog
Audio
Outputs 5-8
Effects Devices
Digital Effects Devices
(set to external sync)
Channel
Outputs 1-4
Tape Returns
or Inputs 1-4
Computer 1
ANALOG OUTPUT ANALOG INPUTAES/EBU OUTPUT AES/EBU INPUT
S/PDIF
INS/PDIF
OUTSLAVECLOCK
INSLAVECLOCK
OUT
7
8
5
6
3
4
1
2
7
8
5
6
3
4
1
2
5/6
7/8
1/2
3/4
5/6
7/8
1/2
3/4

Using the 888/24 I/O 9
To use the 888/24 I/O as a stand alone D/A
converter:
1 Make sure that a digital device providing
a word clock signal is connected to
AES/EBU inputs 1–2 of the 888/24 I/O and
turned on.
2 Turn on the 888/24 I/O. The 888/24 I/O
will search for a valid word clock or a word
clock signal on channels 1–2 of its digital
input ports.
3 When a valid word clock lock is recog-
nized, the 888/24 I/O will enter digital
sync mode and function as a stand-alone
D/A converter using AES/EBU inputs 1–8
and analog outputs 1–8.
The 888/24 I/O D/A sample rate is deter-
mined by the sample rate it detects on
channels 1–2 of its AES/EBU inputs.
✽
The 888/24 I/O defaults to listening to a
digital word clock signal on channels 1–2 of its
AES/EBU digital input ports. To use a S/PDIF
device as your source of word clock, you must
reset this default by opening the 888/24 I/O
and moving an internal jumper switch. See
“Changing the Default Word Clock Lock Port of
the 888/24 I/O in D/A Stand-Alone Mode” on
page 10.
To return the 888/24 I/O to Pro Tools-based
operation:
◆
Turn on your computer.
– or –
◆
If your computer is on, launch Pro Tools.
Changing the Default
Sample Rate of the
888/24 I/O in A/D Stand-
Alone Mode
The default sample rate of the 888/24 I/O
in stand alone A/D mode is 44.1kHz. If you
wish to change this default setting to
48 kHz, you must open the 888/24 I/O and
manually reset it by moving an internal
jumper switch.
To change the default sample rate of the
888/24 I/O in stand alone A/D mode:
1 Make sure that your computer and
888/24 I/O are turned off.
2 With a Phillips screwdriver, remove the
screws from the top of the 888/24 I/O.
3 Using the 1/16 inch hex wrench in-
cluded with the 888/24 I/O, carefully re-
move the front four panel screws as noted
on the bag containing the hex wrench.
4 Lift the top off of the 888/24 I/O.
5 Inside the left-front of 888/24 I/O’s chas-
sis, near the large FPGA chip, is a set of
three jumper switches, each with a remov-
able cap. Each of these switches controls a
different default function which is shown
in Figure 1 and 2.
6 Locate the jumper switch for the default
that you wish to modify and gently lift the
cap off the 3-pronged connector.
7 Place it in the position corresponding to
the value that you desire. For a 44.1 kHz de-
fault sample rate, it should be placed over
the right two prongs. For a 48 kHz default
sample rate, it should be placed over the
left two prongs. Refer to Figure 1 and 2 for
details.

888/24 I/O 10
8 After you have made the desired changes,
replace the top of the 888/24 I/O.
9 Replace the four front panel screws using
the hex wrench.
10 Replace the top screws with a Phillips
screwdriver.
Changing the Default Word
Clock Lock Port of the
888/24 I/O in D/A Stand-
Alone Mode
The 888/24 I/O defaults to “listening” to a
digital word clock signal on channels 1-2 of
its AES/EBU digital input ports. If you wish
to use a S/PDIF device as your source of
word clock, you must reset this default by
opening the 888/24 I/O and moving an in-
ternal jumper switch so that channels 1-2
of its S/PDIF digital input ports are used in-
stead.
☞ Refer to Figure 1 and 2 for details on jumper
switches and their default positions.
To change the default word clock lock port of
the 888/24 I/O in stand alone D/A mode:
1 Make sure that your computer and
888/24 I/O are turned off.
2 With a Phillips screwdriver, remove the
screws from the top of the 888/24 I/O.
3 Using the 1/16 inch hex wrench in-
cluded with the 888/24 I/O, carefully re-
move the front four panel screws as noted
on the bag containing the hex wrench.
4 Lift the top off of the 888/24 I/O.
5 Inside the left-front of 888/24 I/O’s chas-
sis, near the large FPGA chip, is a set of
three jumper switches, each with a remov-
able cap. Each of these switches controls a
different default function which is shown
in Figure 1 and 2.
6 Locate the jumper switch for the word
clock lock default (the back-most jumper)
and gently lift the cap off the 3-pronged
connector.
Figure 1. jumper switch location in the 888/24 I/O
Figure 2. Changing jumper switch settings
stand alone mode
default word clock lock switches
AES/EBU or S/PDIF
stand alone mode
default sample rate switches
44.1 kHz or 48 kHz
stand alone mode
DAC muting switches
in this position
DACs are muted
in this position
44.1 kHz is selected
44.1 kHz
48kHz
unmute DACs
mute DACs
AES/EBU
S/PDIF
remove jumper and
place it in desired position

Using the 888/24 I/O 11
7 Place it in the position corresponding to
the value that you desire. For an AES/EBU
word clock lock port, it should be placed
over the right two prongs. For a S/PDIF
word clock lock port, it should be placed
over the left two prongs. Refer to Figure 1
and 2 for details.
8 After you have made the desired changes,
replace the top of the 888/24 I/O.
9 Replace the four front panel screws using
the hex wrench.
10 Replace the top screws with a Phillips
screwdriver.
Muting the DAC Outputs of
the 888/24 I/O in A/D
Stand-Alone Mode
In certain cases, you may wish to mute the
888/24 I/O’s D/A converters when in A/D
stand-alone mode. This is useful if, for ex-
ample, you need to eliminate potential ex-
ternal analog feedback through a console.
To do this, you must open the 888/24 I/O
and move an internal jumper switch so
that the DACs are muted during stand-
alone operation.
☞Refer to Figure 1 and 2 for details on jumper
switches and their default positions.
To change the DAC output mute setting of the
888/24 I/O in stand-alone D/A mode:
1 Make sure that your computer and
888/24 I/O are turned off.
2 With a Phillips screwdriver, remove the
screws from the top of the 888/24 I/O.
3 Using the 1/16 inch hex wrench in-
cluded with the 888/24 I/O, carefully re-
move the front four panel screws as noted
on the bag containing the hex wrench.
4 Lift the top off of the 888/24 I/O.
5 Inside the left-front of 888/24 I/O’s chas-
sis, near the large FPGA chip, is a set of
three jumper switches, each with a remov-
able cap. Each of these switches controls a
different default function as shown in Fig-
ure 1 and 2.
6 Locate the jumper switch for the DAC
muting default (the middle jumper) and
gently lift the cap off the 3-pronged con-
nector.
7 Place it in the position corresponding to
the value that you desire. To mute the
DACs, it should be placed over the left two
prongs. To unmute the DACs (as in normal
operation), it should be placed over the
right two prongs. Refer to Figure 1 and 2 for
details.
8 After you have made the desired changes,
replace the top of the 888/24 I/O.
9 Replace the four front panel screws using
the hex wrench.
10 Replace the top screws with a Phillips
screwdriver.

888/24 I/O12

Appendix A: Technical Specifications 13
appendix a
Technical Specifications
General
Analog Inputs/Outputs:
■Actively balanced XLR connectors,
outputs internally switchable between
+4 dBu and –10 dBV line levels
Analog Level Trimming:
■Accessible from front panel
Digital I/O AES/EBU:
■8 channel; balanced XLR connectors
Digital I/O S/PDIF:
■2 channel; coaxial RCA connectors
Sample Rate:
44.1 kHz or 48 kHz, ±10ppm
Clock Reference:
■Super Clock (256x) sample clock In/Out;
BNC connectors; additional clock refer-
ences supported via Digidesign's Universal
Slave Driver, SMPTE Slave Driver, Video
Slave Driver and other optional synchro-
nizers
Nominal Operating Level:
■+4dBu; factory calibrated at –18dB
headroom
A/D Specifications
SNR (signal-to-noise ratio):
■≥113 dB (balanced, A-weighted)
■≥110 dB (unweighted)
THD:
■0.003% –0.01 dB @ 1kHz; 20 Hz-20 kHz
(band-limited)
Maximum Input Level:
■+26dB
Frequency Response:
■±1 dB, 20 Hz–20 kHz
Clock jitter:
■< 40pS RMS 22Hz-22kHz BW

888/24 I/O14
D/A Specifications
SNR (signal-to-noise ratio):
■≥110 dB (balanced, A-weighted)
■≥107 dB (unweighted)
THD:
■0.003% –0.01dB @ 1kHz; 20 Hz- 20 kHz
(band-limited)
Maximum Output Level:
■+26 dB/channel (bridging loads)
Frequency Response:
■±1dB, 20 Hz–20 kHz
Physical Specifications
Power requirements:
■90–260 VAC, 47 63 Hz; 30 VA;
auto-switching
Weight:
■7.6 lbs (4.1 kg)
Dimensions:
■2U external rackmount device
19" x 3.5" x 9.75"
(48.26 cm x 8.89 cm x 24.77 cm)

Appendix B: Calibrating the 888/24 I/O (Pro Tools 5.0) 15
appendix b
Calibrating the 888/24 I/O (Pro Tools 5.0)
Before you use the 888/24/I/O Audio Inter-
face, you may want to calibrate its input
and output levels to the level of your mix-
ing console.
The 888/24 I/O is factory-calibrated so that
its input operating level is set to +4 dB
nominal with 18 dB headroom nominal at
full code, unity gain, making calibration
unnecessary for most professional applica-
tions.
If you do need to recalibrate your interface
or other components of your studio, you
can use the alignment procedure described
here.
About Calibration
Calibrating levels on a digital recording de-
vice is different from calibrating levels on
an analog recording device. Unlike analog
devices, most digital devices do not have a
standard “0 VU” level setting that corre-
sponds to nominal input and output levels.
Instead, with an interface such as the
888/24 I/O, the meters are calibrated in
decibels below peak (digital clipping) level.
Headroom
The concept of headroom is slightly differ-
ent for analog and digital devices.
Analog Most analog devices allow for a cer-
tain amount of headroom above 0 VU. If
you send a signal above the 0 VU level to
an analog recorder, you still have a margin
of headroom, and if tape saturation occurs,
it does so fairly gracefully, giving the audio
a compressed sound that some find desir-
able.
Digital Digital devices, on the other hand,
do not allow for signals that exceed the dy-
namic range of the input. When a signal
exceeds the maximum input level for a dig-
ital device, clipping occurs, causing digital
distortion, which is harsh and usually un-
desirable.
The 888/24 I/O provides an industry stan-
dard headroom of 18 dB. The exact value
you use will be determined by the amount
of headroom available in the rest of your
system. For example, if your mixing con-
sole has 15 dB of headroom above nominal
level, then you may want to calibrate the
888/24 I/O to have 15 dB of headroom.

888/24 I/O16
The Calibration Process
Analog To calibrate the input level of an an-
alog device to a mixing console’s output
level, you would typically send a 1 kHz
tone at 0 VU from the console to the ana-
log deck and align the recording deck’s
meters to read 0 VU.
Digital With a digital recording device such
as the 888/24 I/O, however, in order to al-
low for headroom, you must align a 0 VU
tone from the console to a value less than
zero on the 888/24 I/O, by exactly the
amount of headroom that you want.
For example, to have 12 dB of headroom
above 0 VU with the 888/24 I/O, you must
align the incoming 0 VU 1kHz tone to a
level of –12 dB. For 18 dB of headroom,
you would align it to –18 dB. (Since it is as-
sumed that you are using the 888/24 I/O
with a +4 dBu console, a 0 VU signal level
coming out of the console is actually equiv-
alent to a nominal +4 dBu level signal.)
Calibrating The 888/24 I/O
If you are using Pro Tools 5.0 or later, you
can put Pro Tools software in a special op-
erating mode called calibration mode, then
use the Signal Generator Plug-In to gener-
ate a test tone for calibration of the
888/24 I/O.
If you are using Pro Tools 4.3.1 or earlier,
refer to Appendix C: Calibrating the
888/24 I/O (Pro Tools 4.x) for calibration in-
structions.
The Pro Tools Installer includes several pre-
configured calibration session templates
that cover most common calibration set-
ups. You can use these in addition to the
calibration procedure given below.
▲Turn down your monitoring system before
beginning calibration. The Signal Generator
Plug-In emits a continuous signal when in-
serted on a track.
✽During calibration, set all Pro Tools track
faders to their default of 0 dB by Option-Shift-
clicking (Macintosh) or Alt-Shift-clicking (Win-
dows) on any fader in the session.
To calibrate the 888/24 I/0:
1 In Pro Tools, choose Setups > Preferences
and click Operation.
2 Under Output Options, select Direct Out-
puts.
3 At the bottom of the Operation Prefer-
ences dialog, enter a Calibration Reference
Level value (a level of –18 dB is typical).
4 Click Done.
5 Create a new audio track and insert the
Signal Generator Plug-In on the track.
6 Set Signal Generator’s output level. This
should be the same value you entered as
the Calibration Reference Level in step 3.
7 Set Signal Generator’s frequency to
1000 Hz.
8 Set Signal Generator’s signal waveform to
Sine.
9 Route the track’s output to Bus 1.
10 Create a mono auxiliary input track for
each 888/24 I/O output you want to cali-
brate. Set the output assignment for each of
these auxiliary inputs to its respective
888/24 I/O output.
11 Set the input of each auxiliary input
track to Bus 1.