You are here

Fixing Audio Clipping

All about the tools and techniques involved in capturing sound, in the studio or on location.

Fixing Audio Clipping

Postby MusicMadMax » Wed Jul 10, 2013 5:37 pm

Hi folks,

Been out the loop a bit, but now I'm back.

I'm recording my flamenco guitar through a pair of Peluso CEMC-6 mics using Cubase 5. Unfortunately, when I play chords I get Audio Clipping and it's ruining what is otherwise a quite nice recording.

So two questions really:

(1) What actions can I take to prevent it? (other than play more quietly and turn down the levels)

(2) Having recorded clipped notes in an otherwise okay recording, how can I use Cubase 5 to fix the blemishes?

Many thanks,

Max
MusicMadMax
Poster
Posts: 18
Joined: Sun Mar 25, 2012 12:00 am

Re: Fixing Audio Clipping

Postby Hugh Robjohns » Wed Jul 10, 2013 5:50 pm

MusicMadMax wrote:(1) What actions can I take to prevent it? (other than play more quietly and turn down the levels)

You don't need to play more quietly, but you do need to learn how to set your gain structure to ensure there is a sufficient headroom margin to cope with the transient peaks.

You should aim to have an average level of somewhere between -20 and -15dBFS on the DAW's meters, with the highest peaks no higher than -10 to -6dBFS. If in doubt, turn it down rather than up!

(2) Having recorded clipped notes in an otherwise okay recording, how can I use Cubase 5 to fix the blemishes?

Don't waste your time. There are specialist tools that can help, but you're into the domain of turd polishing and it will take considerably longer than simply turning down your mic preamp's gain and playing it again.

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound


Re: Fixing Audio Clipping

Postby shufflebeat » Wed Jul 10, 2013 6:43 pm

1) turn your headphones up.
2) use your delete function.
shufflebeat
Frequent Poster
Posts: 3310
Joined: Sun Dec 09, 2007 12:00 am
Location: Manchester, UK

People with black cats shouldn't get black stair carpet.


Re: Fixing Audio Clipping

Postby Exalted Wombat » Wed Jul 10, 2013 6:49 pm

Do you understand the gain structure through the signal path between microphone and computer? There are several places overload can occur, and it mustn't - at ANY of them!

In particular, you need to present an appropriate level to the input of your computer. An overload at the ADC cannot be subsequently corrected. All you can get is a clipped waveform, quieter.

Want to tell us about your equipment?
Exalted Wombat
Jedi Poster
Posts: 5643
Joined: Sat Feb 06, 2010 12:00 am
Location: London UK

You don't have to write songs. The world doesn't want you to write songs. It would probably prefer it if you didn't. So write songs if you want to. Otherwise, dont. Go fishing instead.


Re: Fixing Audio Clipping

Postby ef37a » Thu Jul 11, 2013 5:04 am

I checked the spec' on that mic and it has a sensitivity of 10mV/Pa, pretty typical for a SDC.
It is also said to cope with 156dBSPL (!) with the 20dB pad engaged so that's 136dB as standard. Surely you would rip the strings off before you got anywhere near that!

That is not to say the pre amps in the AI can cope and that is the most likely point that clipping will occur IMHO..IF you are following Hugh's advice re dBFS levels!

Dave.
ef37a
Jedi Poster
Posts: 7085
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

#They did not listen, they are not listening still...Perhaps they never will?#


Re: Fixing Audio Clipping

Postby Hugh Robjohns » Thu Jul 11, 2013 9:43 am

The mic is very unlikely to be the issue here, Dave. As you've found, it has only a moderate sensitivity and a pretty generous headroom. Equally, I'd be very surprised if the preamp is being overloaded given the mic's sensitivity.

So the most obvious assumption is that the OP has set the preamp gain far too high -- probably because he is working, like so many, under the delusion that you have to peak things close to the top of the meter... and is therefore clipping the A-D in the interface.

Easy thing to fix by updating his working practices.

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound


Re: Fixing Audio Clipping

Postby turbodave » Thu Jul 11, 2013 10:34 am

Hi, If you have been out of the loop as you say , there is a good chance that you are setting your gain like you would for analogue systems. If you are recording 24 bit, don't be afraid to have far lower readings on your meters than you would have done previously. There is always the possibility that you are playing extremely dynamically , and therefore you will need to amend your performance slightly OR adjust your mic and levels (my option of choice)....but the bottom line is that because of the lower noise floor nowadays, you can set your gain with more headroom. Dave
User avatar
turbodave
Frequent Poster
Posts: 1614
Joined: Thu Apr 24, 2008 11:00 pm
Location: derbyshire uk

My head hurts!


Re: Fixing Audio Clipping

Postby Exalted Wombat » Thu Jul 11, 2013 10:35 am

We don't know what interface is between mics and computer. It seems a fair bet that its input gain is turned up too high though.
Exalted Wombat
Jedi Poster
Posts: 5643
Joined: Sat Feb 06, 2010 12:00 am
Location: London UK

You don't have to write songs. The world doesn't want you to write songs. It would probably prefer it if you didn't. So write songs if you want to. Otherwise, dont. Go fishing instead.


Re: Fixing Audio Clipping

Postby ef37a » Thu Jul 11, 2013 12:17 pm

Hugh Robjohns wrote:The mic is very unlikely to be the issue here, Dave. As you've found, it has only a moderate sensitivity and a pretty generous headroom. Equally, I'd be very surprised if the preamp is being overloaded given the mic's sensitivity.

So the most obvious assumption is that the OP has set the preamp gain far too high -- probably because he is working, like so many, under the delusion that you have to peak things close to the top of the meter... and is therefore clipping the A-D in the interface.

Easy thing to fix by updating his working practices.

H

Err? I DID add this caveat Hugh! ".IF you are following Hugh's advice re dBFS levels!"

Dave.
ef37a
Jedi Poster
Posts: 7085
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

#They did not listen, they are not listening still...Perhaps they never will?#


Re: Fixing Audio Clipping

Postby Hugh Robjohns » Thu Jul 11, 2013 12:54 pm

Sorry Dave, I should have been clearer in my response -- I was responding specifically to this line:

ef37a wrote:That is not to say the pre amps in the AI can cope and that is the most likely point that clipping will occur IMHO

It's extremely unlikely that the preamp is clipping because the mic isn't likely to be producing enough signal to overload the preamp. Instead, it is much more likely that the A-D is clipping because the preamp has been set up with too much gain.

I know -- more pedantry -- but the preamp is a separate element from the A-D even though they both coexist in the same box. it is possible to overload the preamp without overloading the converter, and vice versa, and the way of resolving each situation is different.

Hence my attempt at clarification....

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound


Re: Fixing Audio Clipping

Postby planetnine » Fri Jul 12, 2013 7:39 pm

MusicMadMax wrote:Hi folks,

(2) Having recorded clipped notes in an otherwise okay recording, how can I use Cubase 5 to fix the blemishes?


There is a plugin tool for PC, it's not "perfect", but it is bloody amazing what it can do. It might rescue your recording, but it's going to cost you £100 for a licence

-Like Hugh says, I'd re-record if it's an option...


http://www.perfectdeclipper.com/


>
User avatar
planetnine
Regular
Posts: 413
Joined: Sun Sep 12, 2004 11:00 pm
Location: lincolnshire government experimentation zone

Planet Nine, Lincoln, UK.


Re: Fixing Audio Clipping

Postby Hugh Robjohns » Fri Jul 12, 2013 8:11 pm

The declipper in iZotope RX2 is pretty good too, but again costly if you don't already have it. And there's always CEDAR's bureau service if it simply must be fixed cost what may...

But personally, I'd record it again

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound


Re: Fixing Audio Clipping

Postby MusicMadMax » Sun Jul 14, 2013 2:44 pm

Hi all,

Thanks very much for taking the time to reply.

There are people asking about the setup I'm using. It's a pair of Peluso CEMC-6 mics through a DAV BG1 and into a RME Fireface UC.

You say you think the Gain is too high - if this is the case it must be on the BG1, which is turned to the second lowest 'notch' so I suppose I can only go one lower. It can't be the Fireface, because the Gain is already as low as it goes!

I play the guitar just under a foot away from the mics. Unfortunately I can't move further away because the room I'm now in is a load of crap (it's like an IKEA showroom; only the sofas are soft!). When I started the current recording I was doing it in a bedroom which, with hindsight, had great accoustics.

Slightly gutted to re-record it all, having taken so long in the first place (perfectionist or rubbish musician, you decide!) but I'll play with the settings and do some testing. If it solves the issue then I'll just have to man-up and get on with it.

Max
MusicMadMax
Poster
Posts: 18
Joined: Sun Mar 25, 2012 12:00 am

Re: Fixing Audio Clipping

Postby Hugh Robjohns » Sun Jul 14, 2013 3:32 pm

MusicMadMax wrote:There are people asking about the setup I'm using. It's a pair of Peluso CEMC-6 mics through a DAV BG1 and into a RME Fireface UC.


How is the BG1 connected to the RME, Max?

The BG1 does produce a generous output, but the RME's line inputs should be able to cope... provided you have the RME set to the 'hi' mode for its input sensitivity. If it is set for +4 you only have 13dB of headroom, and the -10 mode gives even less...

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound


Re: Fixing Audio Clipping

Postby Exalted Wombat » Sun Jul 14, 2013 7:01 pm

MusicMadMax wrote:There are people asking about the setup I'm using. It's a pair of Peluso CEMC-6 mics through a DAV BG1 and into a RME Fireface UC.

What's the DAV BG1 for? There are two perfectly good mic inputs on your Fireface. It's been demonstrated that the differences between any two competent mic preamps, used in their linear range, are negligible.
Exalted Wombat
Jedi Poster
Posts: 5643
Joined: Sat Feb 06, 2010 12:00 am
Location: London UK

You don't have to write songs. The world doesn't want you to write songs. It would probably prefer it if you didn't. So write songs if you want to. Otherwise, dont. Go fishing instead.


Re: Fixing Audio Clipping

Postby MusicMadMax » Mon Jul 15, 2013 8:13 am

Hugh Robjohns wrote:How is the BG1 connected to the RME, Max?

Straight out the back of the BG1 and into line inputs 3 and 4 of the RME - does that make sense?


Wombat, I got the BG1 because I noticed a difference in the sound when I tested it - it seemed much bigger and richer.
MusicMadMax
Poster
Posts: 18
Joined: Sun Mar 25, 2012 12:00 am

Re: Fixing Audio Clipping

Postby Hugh Robjohns » Mon Jul 15, 2013 8:29 am

MusicMadMax wrote:Straight out the back of the BG1 and into line inputs 3 and 4 of the RME - does that make sense?

Yes, that's fine. So with the BG1 at almost minimum gain, feeding line input at minimum gain it appears you are running out of headroom.

I suspect the issue, then is that the RME is configured with the incorrect sensitivity. As I said above, check that you have it set up in it's 'hi' gain mode which will clip at +19dBu and thus give you a sensible headroom margin. The +4 mode clips at +13dBu and gives 5dB less headroom, while the -10 mode clips at about +4dBu.

I got the BG1 because I noticed a difference in the sound when I tested it - it seemed much bigger and richer.

It is a nice preamp and very good value for money.

H
User avatar
Hugh Robjohns
Moderator
Posts: 16781
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK

Technical Editor, Sound On Sound



Who is online

Users browsing this forum: No registered users and 3 guests