How to use default system sound settings for audio out ?

[lstelie]

Hello,

This is a very newbie question so..

I use Reaper not to record but to play guitar at home, as some kind of VST host .

My setup is : Guitar -> M Audio Fast Track II -> iMac running OSX Lion / Reaper / Amp simulation plugin (LePou)

Everything works fine.. as long as I use headphones.

In Reaper settings I seem to have only one setting to define the audio interface, but no distinct settings for in and out.

From time to time I would like to stop using headphones and use the iMac sound system and fail to find how to do that. I suspect this is "agregate audio device " related, but I don't really understand how it works

So my question :

I succeed to use my external USB audio interface for input and Output, is there a way to use the audio interface for input and the system default for output?

Thanks in advance (and accept my apologies if the question is stupid and the answer obvious)

Luc