DC Offset

Discussion in 'Recording' started by Halifaxsoundguy, Dec 31, 2007.

  1. Halifaxsoundguy

    Halifaxsoundguy Active Member

    Halifax, NS Canada
    I just read this from WIKIPEDIA:

    Would you see this as that one spike on your waveform in protools? Is it possible to remove DC offset after I normalize? The digidesign website doesn't really explain what the DC offset plugins do. How do I start to recognize when to use these plugins?
  2. DrGonz

    DrGonz Active Member

    Phoenix, AZ
    I am only guessing but I feel that most DC offset we are seeing today comes from the computer hardware and mainly I am talking about the DA converters. So maybe its possible your processing is causing an error which I think would affect the DC offset possibly, but I dont know much about anything.... lol. But spikes in the waveform would be really noticeable whereas just some DC offset can be corrected abit or two. Basically, what i am saying is that DC offset shouldnt be detected by an ear or maybe not my ear?

    So where are these spikes? Run a program to test for DC offset in an audio editor(Sound Forge, Wavelab, etc.) Sometimes while mixing a song I will detect little or no DC offset, many mixes rendered later, I then start to detect more. Prolly the plugins I am using and my sound card just cant do it!! right?? I have yet to figure other than that the file I am working on is becoming more corrupted? DC offset is weird :!: I have yet to understand it and I dont think I hear it.... I just havent figured it out yet But I also have heard that DC offset is not such a big problem these days as it was in the good old day... :eek:
  3. IIRs

    IIRs Well-Known Member

    DC can be thought of as a very low frequency sine wave which can be removed using a high-pass filter.
  4. bent

    bent No Bad Vibes! Well-Known Member

    Cocoa, FL
    Home Page:
    DC Offset can occur in many devices, but the most common that I've witnessed is a by-product of poorly built, poorly calibrated ADC's in many consumer soundcards. It's result is a slight shift away from the true zero point of a waveform. If you Google it you can find a lot of tech (and not so tech) explanations. Suffice to say most DAW's can remove it easily. If you suffer from DC Offset the easiest way to get rid of it is to upgrade your ADC.

    Here are a few posts if you want to learn more.
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  5. RemyRAD

    RemyRAD Member

    The DC offset can be observed in your computer waveform display. It's not spikes! The center line of the display will not be centered on the waveform. But rather, the waveform will sit above or below the center baseline indicating either a positive or negative DC voltage potential exists, that has been added to the recorded signal. This can also be a result of leaky electrolytic capacitors within the analog-to-digital converter . This anomaly generally is seen because of an input problem not because of an output problem. But there can also be an output DC offset also due to old capacitors which dry up over time like batteries where out. Especially since they are similar to batteries. Because the computer can record DC voltage values, you are seeing that DC value as an offset, from the center line zero. It's not desirable.

    Frequently, you can eliminate a DC offset by utilizing one of your amplitude oriented functions in software which may include a checkbox to correct for DC offsets. If there is no reference to DC offset try just doing a amplitude change function of "0" or no gain or loss. This may automatically correct the DC offset of that recorded track, so that your waveform appears to be centered above and below the waveform Center baseline. There are no sonic advantages but only disadvantages to DC offsets.

    I frequently see this problem in cheap blaster style sound cards. That's why we don't like them very much.

    Blast those Blasted Blasturds!
    Ms. Remy Ann David
  6. bap

    bap Member

    "Blast those Blasted Blasturds!

    Cute! :wink:
  7. bwmac

    bwmac Active Member

    ROTFLMAO, Remy, you have some awesome one liners.

    for a while I was using the Blaster Audigy 4 Pro 7.1


    the only thing that made me change was the 48khz default converters
    that required another conversion and made original bit importing messed up untill you understand why your sample rate is not what you thought it was to be.

    Other then that I really enjoyed that kit (pci card, breakout firewire box, and software)
    I really miss some of the soft ware since I sold the card and it wont run without the card. say la-ve'

    The system that I have now is far Superior and the 64 bit audio engine is super even though you might say the 64 bit drivers were a blaster to set-up.
  8. RemyRAD

    RemyRAD Member

    Thanks bwmac!

    So you're Audigy Blaster only records at 48kHz? That's dependent upon how you set your software to record. At least should be controlled by the software? I sure wouldn't want to be stuck recording at 48kHz all of the time. It's been a big enough problem when dealing with both audio and television. So convenient we've had two different sample rate standards, one for " music" & one for " TV". It was all a mathematical problem that still has not been resolved properly. LOL! Resolved! Like it will ever happen? It's a resolution revolution! It seems like everything should be simplified with DSD, since I can even add that up. But we'll need room temperature superconductors for that. Maybe in this lifetime? After I retire? If you think we're using too much energy now? Just wait.

    Maybe this will also be beneficial to "50 cent"? He'll graduate to "51 cent".

    52 cent
    Ms. Remy Ann David
  9. bwmac

    bwmac Active Member

    LOL, you will never retire Girl, and I am sure you are much closer to $.99
    ok flatery a side
    what I ment to say was... with the audigy card that I had it was a great clean record all the way up to 192kHz at 24, but no matter what I recorded at, when I rendered it down to a 41kHz 16 wave it would not burn to a CD due to it was not at 41kHz but at 48kHz.
    It didn't matter what I set the render or mixdown quallity to, it always defaulted to 48kHz.
    Once I figured this out, I would move the mixed down wave to sound forge and tweek what I wanted (light mastering) and then save as 41kHz
    actually I thought it was someone on this forum that pointed out to me the blaster 48kHz screw you over bug.
    BTW Remy, How was Christmas, was Santa good to you or were you very nauty last year :lol:
  10. RemyRAD

    RemyRAD Member

    I guess I was too naughty? All I got was dinner. Before I got laid. Laid back that is.

    I have a headache.
    Ms. Remy Ann David

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