Sorry if I'm posting this in the wrong forum.

I recently decided I wanted to record a few samples from movies. For some reason I can't get the stereo mix to work as a way to record, so what I did is ran output 3/4 on my interface (Presonus Firebox) into Inputs 3/4.

This worked fine the first time I used it, was able to record in audacity with no problems. However, tonight I'm getting this terrible effect that almost sounds like I'm recording in a tin can.

Any idea why this would happen? Here's a sample of what it sounds like http://soundcloud.com/jisatsu_koui/recording-issue

Thanks for any help you can give me

This is a classic feedback loop.

Whatever you're recording is being simultaneously played back through the output which is being recorded back in which is being simultaneously played back through the output etc.

You need to get Audacity to stop outputting whatever is being recorded while you're recording it. I don't have much experience with Audacity, but there might be a record monitoring switch or similar somewhere. As a last resort, you could try turning Audacity's sound right down to zero in the Windows mixer (right click the speaker icon by the time in the system tray) while recording, then turning it back up when you need to play back. Not sure if the Windows mixer is available when using ASIO drivers though...

edit: Don't know about the Firebox, but some external soundcards also have record monitoring switches (i.e. located on the actual physical device, not in software.) Check both.

This happened to my friend while we were cleaning up and recording vinyl in Audacity. His laptop mike was picking up what was being played on the speakers and I don't remember what we did to fix it. One thing that would maybe help is turn off speakers while recording (if that's possible)
Also maybe Google this issue, because if it happened to him and now you, it must be common, I've never had an issue, and I think we Googled and found the fix. Sorry couldn't be more helpful. Good luck.

Thanks for the help everyone.

I was able to fix the problem by messing around with the various inputs and outputs, but I need to sit down and figure out what settings work so that I can avoid this from happening again.

If this is the problem (which is what it sounds like to me), go into volume control and mute (or turn down) the microphone input.

Good call on a built in mic as being a possible culprit. Didn't think of that.

We were kind of freaking out to. It was only after I realized that Audacity was recording from the line in (phono), but also the mic was picking up the sound of the records as we played them to record a wave. The only reason I kind of knew what to look for was it sounded like when you talk on a telephone and it's being broadcast on TV or radio and the phone gets this weird feedback loop with these crazy phasey sounds. But I do know we Googled the problem and had it right as rain in no time.