Specifications

Appendix B: TDM Mixing and DSP Usage 601
Mixing with Sends and Busses
Each send will add an input to the destination
output pair. For example, a send to output 1 will
add another input to the output 1–2 mixer. If
the send destination doesn’t already have a
mixer for its output pair, then a new mixer will
be created. A send to bus 3 will make a 1x2
mixer for bus 3 if no other bus 3 sources have
been created yet.
In addition, adding a new track and assigning its
input to a bus source will create a mixer for that
bus pair if there isn’t one already. For example,
creating a new Auxiliary Input track and setting
its input to bus 5 will create a 1x2 mixer for bus
5, even if no sources have been created yet.
Submixing
When the number of channels that must be
mixed exceeds the capacity of a single DSP, ad-
ditional “main” mixers are created automati-
cally, along with summing submixers (which
sum together the “main” mixers). The use of
submixers allows large mix configurations to be
created.
For example, on a Pro Tools HD-series system,
when a Stereo mixer running at 44.1 kHz needs
to grow to more than 68 inputs, a submixer is
created along with another “main mixer” that
provides “n” number of inputs beyond 68. Both
the original 68x2 mixer and the new “N x 2”
mixer which provides additional inputs are
routed to a submixer, and its outputs are finally
sent to the desired destination (such as Output
1–2 on your main audio interface).
Note that any small delays (on the order of a few
samples) that are created remain equal between
these main mixers because they are summed to-
gether by means of submixers, and are not cas-
caded.
The total number of voiceable tracks supported
by your particular Pro Tools configuration will
ultimately determine the maximum number of
channels for your TDM mixer.
Mixers and DSP Hardware
Different mixer plug-ins are available, each of
which uses DSP power at slightly different rates
on the different audio cards (and their DSP
chips), as shown in the following tables.
See also “TDM Mixer Plug-Ins” on
page 606.