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Author Topic: "Remove DC offset (center on 0.0 vertically)" in Audacity  (Read 1648 times)

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Offline jagraham

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"Remove DC offset (center on 0.0 vertically)" in Audacity
« on: January 28, 2018, 02:05:51 PM »
So I've been leaving this box checked while normalizing stereo files in Audacity. I record with Nak CM-100s/300s and they are not matched so the levels vary sometimes depending on recording setup. It just dawned on me I don't even know what this means.

Is this something I should be leaving checked while normalizing the files, or should I be turning this feature off? Does it matter? Have I been helping or harming the resulting wav files in any way?
Mics: Nak CM-300s, Nak CM-100s, CP-1s, CP-2s, AT-853s(Cards, Hypers, Omnis) CA-14s(Cards, Omnis)
Pres: CA STC-9200, CA-UBB
Recorders: Tascam DR-70D, DR-2D, Edirol R-09

ISO: 1 Teac ME-120, CP-3 Caps, AT-853 Subcard Caps

Offline mjwin

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Re: "Remove DC offset (center on 0.0 vertically)" in Audacity
« Reply #1 on: January 28, 2018, 05:04:06 PM »
This option has nothing to do with equalizing the difference in levels between the 2 channels, so you needn't worry.

Audio waveforms are "Alternating Current" & should be, on average, symmetrical about zero. Any  "Direct Current" offset will show up as  a vertical shift in the position of the waveform for that channel. If this is very obvious, it can lead to premature clipping of the signal as, being shifted, it will hit one end-stop before the other. 

Leaving the "remove offset" box checked certainly won't do any harm, as it's good policy to remove any offset before normalizing/exporting the final file, if only to prevent clicks & pops when starting & stopping playback.

If you do see a significant offset, which is quite rare,  it's usually caused by some anomaly in the mic-pre stage, often due to mic power leaking into the input through a faulty capacitor or suchlike.


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