Apple Logic Pro 7 - Manual (Page 378)

378 Chapter 10 Audio Drivers
Core Audio
Logic automatically recognizes any installed Core Audio hardware, and will use the
default settings—defined in Mac OS X’s Audio MIDI Setup utility (Applications >
Utilities > Audio MIDI Setup). It can, however, be advantageous to optimize the settings
for your individual hardware setup, particularly if you use several sound cards or a multi
I/O card. This can be done in Logic’s Core Audio pane, which offers the following
options:
Enable
Click this box to enable the Core Audio driver.
Note: In situations where the preferred hardware is unavailable, such as when opening
a song created in the studio on your PowerBook, or your audio interface is not
connected or turned off, Logic will automatically select the built-in audio hardware of
your Macintosh.
System Memory Requirement
The amount of free memory required outside Logic’s assigned memory is indicated
here. The requirement depends on the settings of the parameters described below. The
memory requirement display is immediately updated when settings are adjusted.
Driver
Allows you to choose between any Core Audio Driver installed in your system,
including the internal sound output.
I/O Buffer Size
This parameter determines the size of the buffer used by the audio hardware—for both
input and output. Options range from 1024 down to 32 samples. The smaller the buffer
size, the less “latency” you will encounter when monitoring while recording, or using
software instruments.
Note: There may be a point where the selected I/O Buffer Size is too small for your
system, and begins to affect playback. This usually takes the form of clicks, pops, and
crackles. You should therefore aim for the lowest possible I/O Buffer Size value that
doesn’t introduce these types of artefacts.
As this parameter value is reduced, it places a higher strain on the CPU(s) of the system.
On current model Macs, you should be able to reduce this value down to its minimum
value. As a word of advice, if you find a higher (larger) I/O Buffer Size setting provides
suitably low latency during record monitoring and software instrument playback, you
should use it. This will minimize the impact on the CPU(s) of your system.