Audio monitoring- external mixer or Mac line-out?

Question

Is it preferable to monitor audio from FCP through an external mixer (Mackie 1202) or is it OK to simply set output to the Macpro line-out?
(I notice the Bars and tone peak at -12- which reads as -10 on my mixer.
For some reason i have always been used to setting my peak at 0 on the mixer
So I'm confused if i should forget the external mixer all together- and just turn it on for the rare occasion I import analog signal)

Answer 1

The main reasons for using an external analog mixer like the 1202 are:
1. if you need a level control for your monitor speakers.
2. if you have other analog sound sources that you want to mix in with your computer output
3. if you need to need two headphone outputs for a voiceover session
For most activities, you don't really need it.
However, monitoring from your headphone output, whether it goes through
a mixer or not, is not the best choice for computer audio.
The best way to monitor your computer's audio is with a Firewire audio
interface, taking digital out from FCP, and using high-quality converters
to convert it to analog. Something like this:
http://www.mackie.com/products/onyx820i/
The meter on your 1202 is for analog signals. Typically you set those
levels to be about 0dB on the Mackie's meter, which should correspond
to +4 dBu on your main analog outputs.
The meter in FCP is for digital audio. On that meter 0dB represents the
absolute maximum, with no headroom, so you'll want to keep your levels
around -12dB, more accurately -12dBFS.
Since the headphone output is not pro, it would make sense that
-12dBFS = -10dBu. In other words, your headphone jack's normal
analog output level is lower than the normal pro audio +4dBu.