Logic Pro 9 User Manual - Help Library - Apple

A post fader signal level, routed to a send, changes along with Volume fader movements.
If you are using the send to route a signal from the channel strip to a reverb inserted on
an auxiliary channel strip, this means that the relationship between the original signal
and the effect signal remains constant. When you pull the channel strip’s Volume fader
all the way down, the reverb disappears as well. This setting is generally the most useful,
and is the default in Logic Pro.
If a send is set to Pre Fader mode, the level of the signal routed to the send remains
constant, regardless of any Volume fader movements on the source channel strip. The
signal is still fed to the selected aux channel strip—even if the source channel strip’s
Volume fader is completely pulled down. Pre fader sends are mainly used for monitoring
tasks: headphone monitoring in the studio or foldback monitoring on stage. Pre fader
sends are also useful when you want to hear the effect signal in isolation (without the
original signal). The equalizer still affects the sends in Pre Fader mode (pre fader, post
EQ).
If you choose Post Pan, the signal is not only post fader, but also post pan. This means
that the pan position of the send signal on the aux (which needs to be stereo or
multi-channel) follows the Pan/Balance or Surround Panner position of the channel strip.
To select one of these options in Logic Pro
µ Click a used Send slot, then choose Post Pan, Post Fader, or Pre Fader at the top of the
menu.
Making Sends Low Latency Safe
If you activate Low Latency mode (see Working in Low Latency Mode), the signal paths
of all sends that create a latency that exceeds the set Low Latency mode limit are muted.
However, if you want to keep a particular send signal path open, you can switch it to Low
Latency Safe mode.
This setting is available in each individual Send menu of audio and software instrument
channel strips, and in aux channel strips that are hosting live input signals.
294 Chapter 10 Working with Instruments and Effects