Specifications

Pro Tools Reference Guide606
There is dissension in the audio community as
to whether or not artifacts that fall within this
area are actually audible in some way. (The nor-
mal dynamic range of human hearing is gener-
ally accepted to fall within a range of around
120 dB, from the threshold of audibility to the
threshold of pain.)
Digidesign has developed a mixer that provides
all of the benefits of the standard mixer plug-
ins, but also provide uncorrelated dither on any
summed output. This provides a steady dither
“noise floor” at extremely low level, which
causes any truncation artifacts to be converted
into steady white noise. However, the addition
of uncorrelated dither requires more DSP horse-
power. As a result, the channel instance count
from the dithered versions of the mixers is
around 15% lower (or more) than the non-dith-
ered standard versions (this varies with sample
rate and mixer type).
For this reason, we offer both types of mixer
plug-in. You may want to use the standard
mixer in most applications because of its greater
efficiency (allowing you to mix more channels
without running out of DSP power), or the dith-
ered mixer because of its theoretical advantages.
A Note About Dithering to 16-Bit
and Dither Plug-Ins
The Dithered mixers provide 24-bit dither at
their summing points. When creating a final
mix that results to 16-bits (for example, for CD
mastering), final dithering should still be han-
dled by plug-ins that provide dither (such as
Digidesign’s Dither plug-in or POWr Dither
plug-in). To properly dither the final mix result,
insert a dither plug-in on the post-fader inserts
of a Master fader. Details about dither and
proper usage of the dither plug-ins can be found
in the DigiRack Guide.
TDM Mixer Plug-Ins
(TDM Systems Only)
Pro Tools HD-series systems come with four dif-
ferent mixers: Stereo, Surround, Stereo Dith-
ered, and Surround Dithered. Pro Tools MIX-se-
ries systems and Pro Tools|24 TDM systems
come with three different Mixer plug-ins: Sur-
round, 24-bit Optimized, and 16-bit Optimized.
In most cases, the Mixer plug-in that was auto-
matically installed with your system is the best
one for all around use. The Mixer plug-in that is
installed depends on which Pro Tools system
you have:
Pro Tools HD-Series Systems The Stereo and Sur-
round Mixer plug-ins are installed by default.
When you run your Pro Tools Installer, a copy
of the Stereo Dithered and Surround Dithered
mixers are placed in the folder “Plug-Ins (Un-
used).”
Pro Tools MIX-Series Systems The 24-bit Opti-
mized Mixer and Surround Mixer plug-ins are
installed by default. When you run your
Pro Tools Installer, a copy of the 16-bit Opti-
mized Mixer is placed in the folder “Plug-Ins
(Unused).”
Pro Tools|24 Systems The 24-bit Optimized
Mixer is installed by default. When you run the
Pro Tools Installer, a copy of the 16-bit Opti-
mized Mixer is placed in the folder “Plug-Ins
(Unused).”