User`s guide

Pro Tools Reference Guide324
24-bit Input and Output with
Pro Tools 24 MIX and Pro Tools 24
Systems
Pro Tools 24 MIX and Pro Tools 24 are full
24-bit audio recording and mixing envi-
ronments, supporting record, playback,
mixing, and processing of 24-bit audio
files. You can record to and from other
24-bit recording systems without any bit-
depth conversion.
24-bit Input and Output with
Pro Tools III Systems
Pro Tools III TDM systems are capable of
24-bit mixing. The only 16-bit restriction is
on recording and playback of audio files.
Digital Input and Output Because PCI-based
Pro Tools III cards are capable of 24-bit
data transfer, your system can send and re-
ceive digital audio with a sample size up to
24-bits directly through the digital inputs
and outputs of an 888/24 I/O, 882/20 I/O,
888 I/O, or 882 I/O Audio Interface. In ad-
dition, mixing within the Pro Tools III en-
vironment (both disk tracks and live inputs
to the audio interfaces) produces a 24-bit
output word. This result can be dithered
down to 16-bits if you are outputting to a
16-bit recorder (such as a DAT machine).
This 24-bit mixing capability is useful if
you work with digital devices such as audio
converters, mastering recorders, or effects
devices that support 20-bit or 24-bit input
and output. It allows you to mix your audio
within Pro Tools with the full 24-bit resolu-
tion of the TDM mixing environment, pro-
viding greater dynamic range and a lower
noise floor.
Analog Input and Output PCI-based
Pro Tools III Systems support full 24-bit
A/D and D/A from the 888/24 I/O Audio
Interface; 20-bit A/D and D/A from the
882/20 Audio Interface; and 18-bit A/D and
D/A from both the 888 I/O and 882 I/O Au-
dio Interfaces. To obtain best results when
recording to disk, you may want to dither
your audio inputs.
☞ For more information about the Dither plug-
In, refer to the DigiRack Plug-Ins Guide.
Mastering and Audio Compression
Although audio compression is often an in-
dispensable tool in analog recording, it can
present problems in the digital domain. If
you compress an input signal at a very high
ratio, you create a signal that contains a
much higher overall power level compared
to its transients. By recording a number of
such signals at the highest possible level on
multiple tracks, you create a scenario that
is more likely to clip the mixed output sig-
nal.
High-power compressed signals, when
mixed together, create an extremely high-
level output. This output may rise above
the full-code level, resulting in clipping. To
avoid this problem, watch the overall level
of your program material—use a meter on a
Master Fader, or use an external mastering
deck’s meters to help avoid clipping. If you
are mastering to hard disk, avoid mixing
full-code audio signals together at unity or
“0” level, as this invariably causes clipping.