Edirol UA-1EX Owner's Manual page 60

Noise or pops are heard when recording/playing
on your computer
Noise is heard during audio playback
Pops/clicks occur during audio playback
Noise is heard in the recorded sound
In Macintosh, check the Energy Saver settings.
In the Mac OS System Setup, set Energy Saver as follows.
60
Click the Sleep tab.
Set "Put the computer to sleep when it is inactive for:" to
Never.
Set "Put the display to sleep when the computer is inactive
for:" to Never.
Click the Options tab.
If there is a Processor Performance setting, set it to Highest.