Logic Glitch- ugly digital scraping noise

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Trem2
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Logic Glitch- ugly digital scraping noise

Post by Trem2 » Tue Jun 09, 2009 3:50 pm

I recorded 3 tracks in logic, listened back and they all sounded fine. I started mixing and to my horror heard a nasty burst of noise about a half second long. Sounds like digital clipping which it can't be cause I recorded at levels well below clipping. The weird thing is when I solo each track to see which one was making this noise, none of them have anything on it but the normal sounding audio. but when i play them all together I hear it, always at the same point in the song !

anyone experienced this? what the hell ?

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Post by ThePitz » Tue Jun 09, 2009 4:31 pm

Sounds to me like you are clipping the master outs. So - none of the tracks are clipping on their own - but when added together they're too loud for the master outs. Have you tried turning down all of the tracks simultaneously? Or turning down the master outs? Maybe the clipping is happening somewhere else in the gain stages? At your monitor amps or something?

Just some guesses. I think it's extremely unlikely that it's a Logic problem. I think it has to be a problem with the way you've gain-staged your outputs - either in logic, or after the sound leaves logic.

What's your monitoring setup?
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Post by Trem2 » Tue Jun 09, 2009 11:28 pm

pretty certain its not a gain staging thing. I know the sound of digital clipping. This sound is similar but WAY louder than any other part of the music. The master bus is metering far below any level that would cause clipping. Its seriously like a burst of insanely loud digital clipping during a really quiet part of the song... loud enough that it sounds like its about to blow my speakers. Anyways...

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Post by ThePitz » Wed Jun 10, 2009 1:20 am

quite odd, indeed - have you tried opening up any other sessions to see if it does it on other songs?

Have you tried exporting your three tracks and importing them back into a fresh new session?

Either one of those causing the noise would certainly narrow the hunt for the culprit.
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Post by ThePitz » Wed Jun 10, 2009 1:23 am

Oh - and also - does it make the noise when just ONE of the tracks is muted? It would be interesting to see if it was a combination of two specific tracks that made the noise - or the lack of one specific track that prevented it.
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Weird noises...

Post by woodhenge » Wed Jun 10, 2009 12:29 pm

Recently I was mixing a song in Logic and had a similar thing happen. My mix had a few dozen tracks, but the combination of 2 overdriven guitar tracks and 1 electric bass track was causing a subsonic buildup at a repeatable point in my song. I stuck a high-pass filter on all the tracks in question and *poof* the noise was gone!

In my case, each channel was well below clipping, and the output bus wasn't getting hit too hard either. But the noise was definitely there! And now it's not. : )

Hope this helps!!!
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Post by Trem2 » Wed Jun 10, 2009 12:47 pm

thanks- I tried re-importing the files into another project and it went away. But still would like to know what caused it so I can avoid it in the future.

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re: weird logic glitches.

Post by woodhenge » Wed Jun 10, 2009 5:11 pm

I've noticed these weird track interactions before in other projects before, now that I think of it. Mine always seems to sound like a damaged speaker hitting the bottom of the basket really hard, even though my monitors are at too low a level for something like that to happen. (Not to mention I'd probably be able to see the speaker moving!) They don't ever seem related to any one instrument, but rather the combination of several tracks. Mute any one of the interacting bunch, and the 'artifact' goes away.

I have narrowed a few other things down that seem to be related, but not really a fix for it. This 'artifact' seems to be way more pronounced when I have something inserted on the main buss... but when I check the meters in whatever plug-in I have inserted are actually WELL below clipping. It makes me wonder... Is the front end of the plug-in where it's getting clipped? Confusing. Something is crunching out somewhere, that's for sure.

Either way, the high-pass thing always seems to work. I've not tried importing into another project, though... I'll have to give that a whirl and see if it works on this recent tune!
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