how do you correct DC offset?

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Johnisfaster
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how do you correct DC offset?

Post by Johnisfaster » Thu Jun 04, 2009 5:08 pm

when using adobe audition I can usually pretty easily come up with DC offset issues, how do you fix DC offsets?
It was as if someone shook up a 6 foot can of blood soda and suddenly popped the top.

8O
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Re: how do you correct DC offset?

Post by 8O » Thu Jun 04, 2009 5:10 pm

A small value capacitor in series...

Or the DC button on the Utility Device...
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3dot...
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Re: how do you correct DC offset?

Post by 3dot... » Thu Jun 04, 2009 5:17 pm

Johnisfaster wrote:when using adobe audition I can usually pretty easily come up with DC offset issues
what what what ?
DC offset in the digital realm is as far as I know...caused by faulty/cheap AD convertors...
in the analog...either XLR cables not wired correctly...or cheap preamps...
highly undesirable...
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3dot...
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Re: how do you correct DC offset?

Post by 3dot... » Thu Jun 04, 2009 5:18 pm

8O wrote:A small value capacitor in series...

Or the DC button on the Utility Device...
...I never checked that...
at work we work with 'Samplitude'...
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djsynchro
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Re: how do you correct DC offset?

Post by djsynchro » Thu Jun 04, 2009 5:21 pm

Real-time DC offset correction works with a high pass filter I think, in SoundForge there is also an off-line function that scans part of or better, the whole file and then corrects the offset.

arachnaut
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Re: how do you correct DC offset?

Post by arachnaut » Thu Jun 04, 2009 5:37 pm

Are you sure this is an issue? For example, a DC offset can occur in physical modelling processes like Karplus-Strong, or even in PWM situations. But it isn't necessarily an issue.

If you remove the DC offset, you will see the waveform center, but so long as there is no true DC involved,
I wouldn't worry about it.

Tone Deft
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Re: how do you correct DC offset?

Post by Tone Deft » Thu Jun 04, 2009 5:41 pm

3dot... wrote:
Johnisfaster wrote:when using adobe audition I can usually pretty easily come up with DC offset issues
what what what ?
DC offset in the digital realm is as far as I know...caused by faulty/cheap AD convertors...
in the analog...either XLR cables not wired correctly...or cheap preamps...
highly undesirable...
more likely it's from a sample that's part of a longer sample. the main sample had no offset but the section he sampled had an offset.


faulty ADC converters??? yeah, you work with them much? c'mon...
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At people who I'd much rather kick in the eye?
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sleepwalkermusic
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Re: how do you correct DC offset?

Post by sleepwalkermusic » Thu Jun 04, 2009 5:44 pm

Hi-pass filter at 10-20hz and you'll get rid of it. Then find out why you're recording with DC. You don't want to be.

3dot...
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Re: how do you correct DC offset?

Post by 3dot... » Thu Jun 04, 2009 11:01 pm

Tone Deft wrote:
3dot... wrote:
Johnisfaster wrote:when using adobe audition I can usually pretty easily come up with DC offset issues
what what what ?
DC offset in the digital realm is as far as I know...caused by faulty/cheap AD convertors...
in the analog...either XLR cables not wired correctly...or cheap preamps...
highly undesirable...
more likely it's from a sample that's part of a longer sample. the main sample had no offset but the section he sampled had an offset.


faulty ADC converters??? yeah, you work with them much? c'mon...
...tell me then... why should any audio recorded have an offset..?

and... actually yes... I'm restoring 20 year old tapes to a computer and remastering it...for about a month now...
loads of DC offset in there from engineers that might be dead already
Last edited by 3dot... on Thu Jun 04, 2009 11:04 pm, edited 1 time in total.
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3dot...
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Re: how do you correct DC offset?

Post by 3dot... » Thu Jun 04, 2009 11:02 pm

sleepwalkermusic wrote:Hi-pass filter at 10-20hz and you'll get rid of it. Then find out why you're recording with DC. You don't want to be.
+1
it should take care of most of it... then you can use a bit of compression...to even out the peaks...
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Johnisfaster
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Re: how do you correct DC offset?

Post by Johnisfaster » Fri Jun 05, 2009 3:49 am

I don't recall exactly how I achieve it but I know that sometimes when mangling a sample in audition I can cause it to happen, I've never really saw it as a problem but from what I understand you're supposed to avoid it. maybe I'm wrong?

also on my modular rig one of my filters can cause it from what I've read.

so a high pass filter should help?
It was as if someone shook up a 6 foot can of blood soda and suddenly popped the top.

Tone Deft
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Re: how do you correct DC offset?

Post by Tone Deft » Fri Jun 05, 2009 3:53 am

Johnisfaster wrote:so a high pass filter should help?
yes.

think about it for a moment... DC is literally the lowest frequency there is. 1 Hz, 0.9Hz, 0.1Hz, 0.000001Hz... 0.000000000000000000...Hz, DC is NO oscillations, 0Hz, at least that's how the maths work out. so, high pass filtering with the corner frequency set as low as possible will do the trick, or an audio editor with DC removal or ye good ol' Utility plug in.

I might shy away from filters only because you'd be pushing the filter's limits, there might be phase issues or something. in designing a filter people don't really consider DC removal, they tune it for the more usable range. I would think.
In my life
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At people who I'd much rather kick in the eye?
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Johnisfaster
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Re: how do you correct DC offset?

Post by Johnisfaster » Fri Jun 05, 2009 4:01 am

I figured it out, it's when I copy a wave that has a lot of low end and then modulate paste it on top of itself it DC offsets the whole wave. that is unless I totally misunderstand what DC offsetting is. But high pass filtering brings it back to normal
It was as if someone shook up a 6 foot can of blood soda and suddenly popped the top.

Tarekith
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Re: how do you correct DC offset?

Post by Tarekith » Fri Jun 05, 2009 5:37 am

DC Offset is a weird thing, it seems the strangest (or most mundane) process will bring it on, and the benefits of removing it are usually negligable in most cases. I scan all my mastering jobs for DC offset at the beginning, but unless I see a difference in offset greater than say 0.05 between the left and right channels, and with a value greater than 0.1, I rarely bother correcting for it.

Johnisfaster
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Re: how do you correct DC offset?

Post by Johnisfaster » Fri Jun 05, 2009 5:41 am

I think in my case and what I'm doing with adobe audition it's well worth correcting though, for instance if I leave it there the master meter stays really high and doesn't bounce much, if I remove DC all the sudden the master is bouncing quite a bit and I can't actually even hear a difference, but the wave looks very different.
It was as if someone shook up a 6 foot can of blood soda and suddenly popped the top.

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