Specifications

HD I/O Guide38
For example, to have 12 dB of headroom above
0 VU with the HD I/O, you must align the in-
coming 0 VU 1kHz tone to a level of –12 dBFS.
For 18 dB of headroom, you would align it to
–18 dBFS. (Since it is assumed that you are using
the HD I/O with a +4 dBu device or console, a
0 VU signal level coming out of the device or
console is actually equivalent to a nominal
+4 dBu level signal.)
Calibrating the HD IO
To calibrate HD I/O, enable Calibration mode
and use the Signal Generator plug-in to generate
a test tone for alignment.
The Pro Tools installer includes a standard
eight-channel calibration session for the
HD I/O. You can use this session as is and
change the input and output assignments for
more HD I/O channels or use it as a base to make
your own calibration template.
The following instructions show how the cali-
bration session was created. You can create a ses-
sion from scratch or open the calibration tem-
plate and walk through these instructions.
To calibrate the HD I/O Outputs:
1 Launch Pro Tools and create a new session.
2 Choose Setup > Preferences and click the Oper-
ation tab.
3 Enter the desired Calibration Reference Level
value in dB. A level of –18 dB is typical. (It is not
necessary to type a minus sign here.)
4 Click OK.
5 Create a new mono audio track by choosing
Track > New.
6 Insert the Signal Generator plug-in on the
track.
7 Set the Signal Generator plug-in output level.
This should be the same value you entered as
the Calibration Reference Level (such as –18 dB).
8 Set the Signal Generator frequency to
1000 Hz. 1000 Hz is typical, but any frequency
will work. Other typical values are 250 Hz and
500 Hz.
9 Set the Signal Generator signal waveform to
Sine.
10 Route the track’s output to Bus 1. In the cal-
ibration template, Bus 1 has been renamed to
“1k Tone.”
11 Create a mono Auxiliary Input track for each
HD I/O output you want to calibrate. Set the
output assignment for each of these Auxiliary
Inputs to its respective I/O output.
12 Set the input of each Auxiliary Input track to
Bus 1, or 1k Tone for the template session.
13 Create an additional mono Auxiliary Input
track for each input you want to calibrate. Set
the input assignment for each of these Auxiliary
Inputs to its respective I/O input. Then set the
output of each of these Auxiliary Inputs to an
unused bus pair (for example Bus 3–4). In the
template session the bus names are Null and
Out. This makes sure feedback doesn’t occur
when monitoring main outputs 1–2.
14 Connect an external VU meter to each of the
I/O outputs in turn. (One at a time as you cali-
brate.)
15 Set all Pro Tools track faders to their default
of 0 dB by Option-clicking (Mac) or Alt-clicking
(Windows) any fader.
Turn down your monitoring system before
beginning calibration. The Signal Genera-
tor plug-in emits a continuous signal when
inserted on a track.