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Need help on setting up aggregate device


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Ok, so this is what I'm trying to do:

I want to set up an aggregate device so that I can use a USB microphone and built-in output as the output (headphone) with the PreSonus AudioBox USB audio interface (because I still use computer speakers and a crappy USB microphone). I also have a synth connected to the audio interface, so I still want to be able to use the AudioBox's inputs to record sound from the synth. What I did was try to set this all up using Audio MIDI Setup.

 

Here's a screenshot: http://dl.dropbox.com/u/72821018/Screenshots/Trying%20to%20set%20up%20aggregate%20device.png

 

In Logic's core audio preferences, I chose the aggregate device I just created (USB mic + audio interface). I couldn't get any sound coming out of my computer speakers or any input into the USB microphone. What am I doing wrong here? :?

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Ah, I totally forgot about trying that. I found out Input 3 was for the USB mic and Out 3-4 was for the built-in output. Thanks!

 

But now I have another problem: when recording or monitoring the inputs for the USB mic or synth (which is input 1 and 2), I seem to get a weird, unwanted distortion + delay effect on the audio. What could be causing this? I don't seem to have this problem with the audio generated by software instruments in Logic.

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Anyone? :(

 

Oh, and here's a little video showing you what I mean (if you can't see what's happening, watch in HD) :

 

 

(I apologise for not using a screen recorder, because I couldn't get the sound to record.)

 

I'm running a simple sawtooth wave on a C4 note into the input of the audio interface just as an example (because I'm sure most of us know what a sawtooth wave sounds like, right?).

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Your audio track has its "I" (Input Monitor) on. You have a mic on input 1, and your monitors are on, so you're creating a feedback loop.

 

Your signal chain is a mic -> speaker. So your mic is picking up noise, the noise is amplified and reproduced by the speaker, the mic picks up that amplified noise, which is amplified again and played by the speakers... etc. On top of that, the latency creates the delay effect.

 

Use headphones, or turn off the input monitoring for the mic.

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Your audio track has its "I" (Input Monitor) on. You have a mic on input 1, and your monitors are on, so you're creating a feedback loop.

 

Your signal chain is a mic -> speaker. So your mic is picking up noise, the noise is amplified and reproduced by the speaker, the mic picks up that amplified noise, which is amplified again and played by the speakers... etc. On top of that, the latency creates the delay effect.

 

Use headphones, or turn off the input monitoring for the mic.

Thanks for the reply David!

 

I tried turning off input monitoring for the mic just as you suggested and I even deleted the audio track, but the problem still exists, so I think this might be another problem.

 

I’ll also mention that I changed the order of the aggregate device since I posted that last screenshot, so it makes it a bit more convenient for me:

http://dl.dropbox.com/u/72821018/Screenshots/Trying%20to%20set%20up%20aggregate%20device%20pt%202.png

(The USB mic is the one that says AK5370)

 

What I mean by 'more convenient for me' is that all my old projects use Out 1-2 as the output (which would be the default built-in output), and If I were to go back to an old project, I would have to change all the outputs to Out 3-4 which would be a bit annoying. Is the way I set up the aggregate device causing the problem?

 

Not sure if this helps, but I set my external instrument to inputs 1-2:

http://dl.dropbox.com/u/72821018/Screenshots/External%20instrument%20settings.png

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