Mastering & DC offset

  • Thread starter Thread starter ecktronic
  • Start date Start date
ecktronic

ecktronic

Mixing and Mastering.
I just heard about DC offset recently and was wondering if its the norm to remove any DC offset before mastering commences?

I found 1 of my mixes to have a DC offset of -0.008% Left and -0.009% Right.
Is this a big DC offset?

And what produces DC offset in mixes? Is it poor mixing?

Cheers,
Eck
 
I read an article, I think in "Recording", that suggested doing dc offset correction, as a rule, for all the tracks (individually), at the start of your mix...

As far as mastering and such, I imagine you'd do it one last time at that step...
 
Cheers man.
Ive noticed some strange looking snare hits in some of my snare tracks.
They are really big at one side then kinda mad looking at the other,.
oh well too late for removing DC offset on each track. :rolleyes:

Eck
 
ecktronic said:
oh well too late for removing DC offset on each track. :rolleyes:

Eck
Click to expand...

Why, you can just select the track and remove DC offset. Or have you allready mixed down and sent it out?
 
lomky said:
Why, you can just select the track and remove DC offset. Or have you allready mixed down and sent it out?
Click to expand...
Ive already mixed down and I cant be bothered rendering each track seperately then removing DC offset then bouncing down to stereo mix for 12 songs of 40 odd tracks each!
You could call it lziness, but Im getting tired of this album.

Eck
 
if you're really worried about it, just put a High Pass filter at 1hz on the mix.
 
FALKEN said:
if you're really worried about it, just put a High Pass filter at 1hz on the mix.
Click to expand...
Does that totally elminate all DC offset?
I hi pass all my tracks to 20Hz and I still had a stereo mix with a DC offset of 0.008%.
I suppose thats pretty small but I dont know if thats negligable or not.

Cheers,
Eck
 
ecktronic said:
Cheers man.
Ive noticed some strange looking snare hits in some of my snare tracks.
They are really big at one side then kinda mad looking at the other,.
oh well too late for removing DC offset on each track. :rolleyes:

Eck
Click to expand...
That's pretty normal. Lopsided waves aren't rare - Percussion, many vocalists, most horns, some wind and reeded brass -
 
ecktronic said:
Cheers man.
Ive noticed some strange looking snare hits in some of my snare tracks.
They are really big at one side then kinda mad looking at the other,.
oh well too late for removing DC offset on each track. :rolleyes:
...
I hi pass all my tracks to 20Hz and I still had a stereo mix with a DC offset of 0.008%.
Click to expand...
Like John says, that snare stuff is not necessarily offset, that's probably just lopsided waves, which is a natural representation of most real-life instruemnts such as snares. Completly different animal than offset.

Which is why I'm wondering where you're getting your "offset percentages" from. If you're just reading the overall energy balance between positive and negative, that's not reading offset unless you know your input waveform is balanced to begin with (e.g. a test instrument sine wave).

Offset is usually referred to terms of dB, representing the "resting level" or "zero crossing level" of the signal; i.e. where the "flat line" of that track with no signal is located. If that flatline/rest level is at -infinity dBFS (dead center), but the peaks are lopsided in one direction or another, that's not offset. That's natural. If, however, the flatline/rest level is not at center, *then* you have offset.

G.
 
DC offset is yet another example of how you can have too much metering - until we had DAWs with the ability to look for DC, we just listened. Use your ears, not your meters.

If you aren't hearing 'clicks' when you start and stop playback, then why do any further processing to the file(s)?
 
bblackwood said:
DC offset is yet another example of how you can have too much metering - until we had DAWs with the ability to look for DC, we just listened. Use your ears, not your meters.

If you aren't hearing 'clicks' when you start and stop playback, then why do any further processing to the file(s)?
Click to expand...


well, before DAW's we didn't have crappy converters to create a DC offset problem.
a DC offset consumes head room, not to mention the speakers aren't going to be returning to their resting point. And then if you combine one track with DC offset to another one without it...you just combine the problem. And the ears don't pick this up as easily.

I'm an advocate of doing FALKEN suggested. Putting a hi pass filter on the entire mix. It also removes any subsonic frequencies that you might not be able to hear. 20Hz or below usually (depends on what the mix is).
 
bennychico11 said:
well, before DAW's we didn't have crappy converters to create a DC offset problem.
Click to expand...
Sorry, this is incorrect - we've had digital converters for about 3 decades, the first DAW that checked for DC offset probably appeared 10-15 years ago.

Crappy converters? That's all there was in the first 15 years of digital.

Continue as you wish, but at some point you have to ask yourself if unnecessary processing is good or bad.
 
bblackwood said:
Sorry, this is incorrect - we've had digital converters for about 3 decades, the first DAW that checked for DC offset probably appeared 10-15 years ago.

Crappy converters? That's all there was in the first 15 years of digital.

Continue as you wish, but at some point you have to ask yourself if unnecessary processing is good or bad.
Click to expand...


no, that's true.....but what I was getting at was before digital we had analog which is why we didn't see any problem. Cheap gear (or problematic gear) can usually give you the DC offset. I think we get more problems now with products like Sound Blaster and such that are marketed towards the consumer market than we did in the past when gear was concentrated more on the professional market.
But DC offset tools aren't just used in the DAW world...take a look at an oscilloscope.

I can't see why putting a 1Hz hi pass filter (or even 20Hz) is going to harm your mix. If anything it's cleaned up a lot of my stuff. And I do a lot of audio for video...which you come across a lot of problems in. DC offset, low frequency problems (remember, low frequencies consume up a lot of headroom as well). I don't see it as unnecessary.
 
Funny, I just had a bunch of tracks come in that were poorly done, and they had something like 3% DC offset. Very obvious on the graphical display. It is weird, where the flat line normally is (-infinity) these tracks have their flat line at around -30.5 on the negative (bottom) side of the scale. Not sure that makes sense to anybody, but sure enough a highpass filter brought it back up to where it should be. Of course the "remove DC offset" command works too. This is an extreme case where correcting the offset certainly gives you a few more db of headroom. No idea what they were using to create this, but there are quick little digital pops occassionally too. Crazy Mexican DAWs...
 
During mixing it's not uncommon (actually very common) to use filters to high pass and low pass the frequencies of the tracks that aren't contributing to the mix. I can't see where anything in the 20 Hz range of a snare track would be contributing anything to the mix so a high pass here (or more like 30-40 Hz for a snare) shouldn't do any damage and take care of the DC offset issue.
 
Last edited:
One question I have had about this subject ever since I started using NLEs is, is there any source of information describing just how the "DC Offset" process in the various software titles does it's job? Not analog offset circuitry, for which there is a plethora of information. but digital software processing.

I would think - but I really don't know - that a proper digital DC Offset algorithm would perform a simple value shift. In other words it would just re-offset the data to counter the offset, rather than apply a LF filter to the signal. Am I wrong to think that would be (at least theoretically) a much more transparent way of countering offset than the application of a filter to the signal.

While one may often apply a LF filter to a track to get rid of mud anyway, this is not always the case. In such cases, if given the choice, I'd rather just shift bit values down (or up) by a simple amount than apply a filter transform.

Maybe it's splitting hairs, maybe not. But I's something I've always wondered.

G.
 
Just curious.

Everyone in this thread who has mentioned "seeing" DC Offset......Did you hear any difference when you removed it???
 
RAMI said:
Just curious.

Everyone in this thread who has mentioned "seeing" DC Offset......Did you hear any difference when you removed it???
Click to expand...
You mean other than the pop or click at the beginning and end of the clip? ;)

The difference can be quite subtle, but yes it can sometimes be audible if the offset is big enough, depending upon the quality and design of the loudspeaker it's being played through. Because the DC current holds the speaker at a "rest position" different from it's natural zero voltage rest position, offset causes the loudspeaker to operate under potentially different physical operating conditions (throw, damping, etc.). This *can* - but not always will - audibly affect the sound.

G.
 
SouthSIDE Glen said:
You mean other than the pop or click at the beginning and end of the clip? ;)
Click to expand...
Oh, is that how you know if it's offset or not??? I didn't know that.

Does that mean that if I don't get those pops, I'm OK??? Or it's not as simple as that???
 
You must log in or register to reply here.
Back
Top