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DC Offset in mastering - how much does it matter

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DC Offset in mastering - how much does it matter

Postby Mick C » Tue Nov 10, 2020 11:59 pm

I work in Studio One and it has a meter showing DC offset in the mastering Project Page.
Whilst I know what DC offset is - I don't know how important it is.

Here's why I'm confused:
I have a song that the meter reports as having L & R DC offset at infinity dB. If I make a subtle change on a limiter, re-check, and it now reports -84L / -102R. Another subtle limiter change and its now -87L / 0R, and another back to infinity L&R, and another -89L / -108R. It feels like I could do this all day...
So I imported Elbow's "One Day Like This" from a CD, and running the same test yielded a DC offset of -76.7L / -77.8R

But in all these experiments I can't actually hear a difference. So my question is twofold:
a) is it something I should be concerned with at all?
b) if it is then what kind of target figure should I aim for, and how would I go about it?

Thnks
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Re: DC Offset in mastering - how much does it matter

Postby James Perrett » Wed Nov 11, 2020 1:48 am

True DC offset matters if you are editing material with a DC offset in with something with a different (or no) DC offset because you'll end up with clicks or thumps at the joins. However, I doubt that you are seeing a real DC offset as most hardware can't record down to DC (although some convertors do and it is becoming more fashionable for people to use audio channels to record synth control signals which do require a response down to DC).

What you are really seeing is an imbalance in positive and negative going signals which is probably simply down to the type of waveforms that you are recording. The human voice produces asymmetric waveforms and brass instruments are even worse. However, the imbalances that you are seeing are very small and probably not worth worrying about.

The only reason to worry is if you are trying to squeeze the absolute highest level out of the end product. Pop radio stations use phase rotation in order to make asymmetric waveforms more symmetrical which allows them to increase the level a little more without obvious artefacts but I've not heard of it being used for music production.
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Re: DC Offset in mastering - how much does it matter

Postby Hugh Robjohns » Wed Nov 11, 2020 1:54 am

I think James has explained what's going on very well. You're seeing the effects of asymmetrical waveforms -- and that asymmetry will inherently change with different dynamics settings.

But as long as the reported offset is below about -75dB I wouldn't worry about it at all.

...but if you are still worried about it, most DAWs (and some plugins) have a DC-offset filter option somewhere.
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Re: DC Offset in mastering - how much does it matter

Postby Mick C » Wed Nov 11, 2020 4:37 pm

Thanks James & Hugh for the advice.

Studio One has a plugin called Mixtool, which includes a switch labelled 'Block DC Offset' so for fun I followed your lead Hugh, and inserted it systematically at the start, end, and between every plugin within the mastering chain, and it made no difference at all.

I won't worry about it. Clearly my vocal is asymmetric and very offsetting - as anyone that's heard me sing will testify :lol:

thanks again guys
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Re: DC Offset in mastering - how much does it matter

Postby Hugh Robjohns » Wed Nov 11, 2020 5:17 pm

Mick C wrote:Studio One has a plugin called Mixtool, which includes a switch labelled 'Block DC Offset' so for fun I followed your lead Hugh, and inserted it systematically at the start, end, and between every plugin within the mastering chain, and it made no difference at all.

Perfect. Then you know you have no DC offset, just normal asymmetrical waveforms!
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