Logic doesn't clip anymore

Pleae help me... I don't know why but today I opened my last project to record some voices and an acoustic guitar and... the peak meter of every audio track doesn't go beyond the 0 Db Fs even if i hit strongly the microfone with the gain at maximum level. Logic can't tell me anymore if I'm clipping when I record and even when I'm just playing. I have no limiter on the tracks. The signal just reaches the maximum level and goes far beyond and I hear the clip but logic seems not recognizing it. It just reaches the 0 db. The peak meter never becomes red. I also opened a new project with only one audio track... and nothing changed. I restarted Logic, I restarted my mac... nothing to do. I am not able to record in this situation. Can anyone help me please? It's a very very strange situation.

You shouldn't be approaching anywhere *near* 0dBFS when recording anyway.

 

Logic can't get anything over 0dBFS from the interface - if you've clipped the interface, the most it can deliver to Logic is 0dBFS. The proper way of handling this is to record at standard practice levels, which is *way* down from where you are...

Hi Skansa,

Beej is right.

Download PDF, read and apply:

http://www.logicprohelp.com/viewtopic.php?t=57055

Yeah I know I should record not around the 0 Db, the right level should be around -6 or -8 Db. Anyway I don't know why logic doesn't warn me anymore when I reach the 0 or I go beyond it with some transients.

It's very strange

First of all, Logic never did any sort of warning when you clip a recording.

The meters would go into the red and that's it.

 

Does this happen when you create a new project from scratch?

 

Looks like there's some limiting going on somewhere in that project.

Have you checked the Environment for an input track that doesn't show in Arrange?

First of all, Logic never did any sort of warning when you clip a recording.

 

I seem to remember it did once - basically, once you had hit stop, Logic would iirc do a clipscan and if it encountered several 0dBFS samples in a row, it would pop up a "This recording may be clipped" alert.

 

However, I don't think it does this anymore (with 24-bit recording, people should be recording around -18dBFS on average and so the overhead of scanning the recording looking for potential clips is quite large).

 

There is plenty of headroom to avoid the potential of clipping, and in any case, clipping is more a function of the interface than the software recorder, as the recorder is only writing what it's given to disk - it's the user's responsibility to set the interface to not clip recordings.

First of all, Logic never did any sort of warning when you clip a recording.

 

I seem to remember it did once - basically, once you had hit stop, Logic would iirc do a clipscan and if it encountered several 0dBFS samples in a row, it would pop up a "This recording may be clipped" alert.

 

You're right. Was it in Logic 7?

http://www.logicprohelp.com/viewtopic.php?t=17788

Yep, Logic 7. It's been a while, no wonder I forgot about the clipping warning.

Ok guys the fact is very simple:

 

the peak meter does not go on red even if I clip. I tried in post fader metering, in pre fader metering, I tried opening one audio track in one new empty project... nothing.

But in Pro Tools everything works well. So it's not an hardware problem.

 

My audio chain is very simple at all:

 

Microphone (beta 57a) - Cannon - Mbox2 - Mac Usb - Logic.

 

No limiter before logic, no limiter after.

It clips only in play, but in recording the peak never goes red.

Does this happen when you create a new project from scratch?

 

Looks like there's some limiting going on somewhere in that project.

Have you checked the Environment for an input track that doesn't show in Arrange?

 

What about these two questions I asked earlier?

the peak meter does not go on red even if I clip.

 

Think about it. A digital clip in fixed point is when a signal goes over 0dBFS. Firstly, the faders/mixer channels in Logic are already in 32f float so they don't really clip at all, but to keep things simple, the meters will display the incoming level of the audio coming in from the interface while recording.

 

The red meters kick in at *above 0dBFS* - ie, on a fixed point recording, a clip is when audio goes at or over 0dBFS for more than a few samples. So, if the audio went over 0dBFS, the meter would go red.

 

Why then does the meter not go red?

 

Because Logic *can never receive a signal over 0dBFS*. The interface will clip, it will provide a bunch of 0dBFS samples, but it cannot send +0.1dBFS or anything, because it's sending a fixed point audio stream, and with no headroom, there is literally no where to go.

 

Operating at zero headroom, whether analog or digital, is a big engineering no-no and you really should know better.

 

Now, you could argue that it might be nice in Logic to have some function that alerts you when it gets a bunch of 0dBFS samples in a row, and like I say, in older versions there was a facility for this, but as far as I know it's been removed for some reason, so the developers clearly thought the feature was either not that useful, or the overheads to provide that feature outweighed it's benefits.

 

I say again - you should be nowhere near 0dBFS, and if you are, you only have poor engineering skills to blame, rather than Logic.

 

Setting levels before recording and ensuring you have plenty of headroom is a basic fundamental. If you don't do this, you'll get bad results. Simples.

I see this when my interface clips:

 

http://farm6.static.flickr.com/5131/5500221013_3a96bed4fb_m.jpg

 

Pretty clear 'interface clips!' warning. No verbose message required or even wanted.

The OP is stating that there's "no red".

So methinks he's not hitting the 0 dBarrier in Logic. Probably the input settings on the Audio window of the Audio MIDI Setup Utility might be of help there - after reading and internalizing things outlilned in "the Lagerfeld paper", of course. 8)

 

I see you have an M-box. I don't know those, but I have heard they can be tricky to get working correctly with Logic. Anyway, if somehow it can't be done from Audio MIDI Setup, check its' proprietary input and output level setting software.

Cool - presumably Logic removed the clipscan after recording feature, and instead has a meter metric to light the over clip led if it detects a few 0dBFS samples in a row, then.

 

If the OP isn't getting this, he may indeed not be clipping Logic - maybe there is some processing in the interface drivers that mean it never delivers full 0dBFS, despite the interface clipping.

I see this when my interface clips:

 

http://farm6.static.flickr.com/5131/5500221013_3a96bed4fb_m.jpg

 

 

What interface are you using?

I have to tell something to Beej.

Why one enters this forum asking for some help and receives comments like "you should blame your engineering skills rahter than logic"?

I know what is Dbfs and working with digital and I know what is DbU and working in analogic. I know I should never reach the 0 DbFs, it's... Logic.

What I don't know is why 5 days ago Logic peak meter of audio tracks became red when ACCIDENTALLY clipping also telling me the amount of overclipping (the peak meter gone red and the number telling me 4 or 5 or 2 for example). Now it doesn't happen anymore. And now, even if I really know I should never record near the 0 DbFs, I can't recognize if some transients accidentally gone over the 0 DbFs when recording just because the peak meter never goes red... I can't record in this situation. Maybe I have installed an AU that made some disorder in logic drivers or preferences... don't really know. I'm asking everybody if there's a preferences o settings that I might have touched accidentally... Thanks

Does this happen when you create a new project from scratch?

 

Looks like there's some limiting going on somewhere in that project.

Have you checked the Environment for an input track that doesn't show in Arrange?

 

What about these two questions I asked earlier?

 

I'm asking for a third time now...

I have to tell something to Beej.

Why one enters this forum asking for some help and receives comments like "you should blame your engineering skills rahter than logic"?

 

Well that's not exactly the *only* thing I said, is it?

 

What I don't know is why 5 days ago Logic peak meter of audio tracks became red when ACCIDENTALLY clipping also telling me the amount of overclipping (the peak meter gone red and the number telling me 4 or 5 or 2 for example).

 

It's not possible on recording. The audio interface cannot supply anything over 0dBFS. Full stop. You only get an indication of how much over 0dBFS you are on playback, if you've increased your levels or added plugins to increase the level.

 

The audio interface cannot supply a +4dBFS signal to Logic so Logic can say "you're over by 4dB". It's not possible. Therefore I think either your memory is innaccurate, or you had something else going on (like monitoring through a plugin and the plugin itself was adding gain through the monitoring/metering path.)

 

I can't recognize if some transients accidentally gone over the 0 DbFs when recording just because the peak meter never goes red...

 

As Erik has demonstrated, it does for him, so perhaps you are not hitting the 0dBFS ceiling.

 

I can't record in this situation.

 

It should be pretty simple for you to test out the behaviour of your system to verify what behaviour you get with your gear and workflow.

 

Maybe you might want to invest in a hardware limiter to make sure you never get overs.

 

Maybe I have installed an AU that made some disorder in logic drivers or preferences... don't really know. I'm asking everybody if there's a preferences o settings that I might have touched accidentally... Thanks

 

Nope, don't think so. You need to run some tests and verify the behaviour so you understand what's going on and why...

I see this when my interface clips:

 

http://farm6.static.flickr.com/5131/5500221013_3a96bed4fb_m.jpg

 

 

What interface are you using?

 

"Interface" is a big word... it's in my sig, the Samson Gomic... It has a simple led that is green when not clipping (-0,1 dB) and red when clipped (0 dB).

Beej is actually correct.

Logic 8-9 got rid of the 0 dBFS and so many samples warning.

 

The only way to get the red warning light while recording is if the signal is being amplified(and therefore clipped) in the digital domain.

 

You can easily test this if you have use the internal microphone of an iMac or MacBook.

This is being amplified digitally.

I see this when my interface clips:

 

http://farm6.static.flickr.com/5131/5500221013_3a96bed4fb_m.jpg

 

 

What interface are you using?

 

"Interface" is a big word... it's in my sig, the Samson Gomic... It has a simple led that is green when not clipping (-0,1 dB) and red when clipped (0 dB).

 

This is being digitally amplified.

If you try it with an analog preamp you won't get it to clip(as it should be as beej has eloquently explained. )

If you try it with an analog preamp you won't get it to clip(as it should be as beej has eloquently explained. )

 

Thanks for the confirmation, Eric - I didn't have time to check out the behaviour for myself.

If you try it with an analog preamp you won't get it to clip(as it should be as beej has eloquently explained. )

 

Thanks for the confirmation, Eric - I didn't have time to check out the behaviour for myself.

 

Don't mention it.

Thanks Bradley,

I tried with the built in microphone and it clips a lot... my memory should have played a bad trick!

Actually I thought about the fact that the audio interface itself cannot give a signal that goes over 0Db... it's simply impossible. The clip forms in the audio device and then it becomes a square wave that reach the 0Db but never goes beyond just because the digital domain can't interpret anything over the 0. So the waveform arrives in logic already distorted with the peak of the square wave that gently caresses the 0Db... that's why logic can't clip in recording.

Am I right?

Actually I thought about the fact that the audio interface itself cannot give a signal that goes over 0Db... it's simply impossible. The clip forms in the audio device and then it becomes a square wave that reach the 0Db but never goes beyond just because the digital domain can't interpret anything over the 0. So the waveform arrives in logic already distorted with the peak of the square wave that gently caresses the 0Db... that's why logic can't clip in recording.

 

Exactly.

Thanks Bradley,

I tried with the built in microphone and it clips a lot... my memory should have played a bad trick!

Actually I thought about the fact that the audio interface itself cannot give a signal that goes over 0Db... it's simply impossible. The clip forms in the audio device and then it becomes a square wave that reach the 0Db but never goes beyond just because the digital domain can't interpret anything over the 0. So the waveform arrives in logic already distorted with the peak of the square wave that gently caresses the 0Db... that's why logic can't clip in recording.

Am I right?

 

Spot on.