What is DC?

  • Thread starter Thread starter Chewie
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Chewie

Chewie

New member
I keep seeing this term all over recording software. What does it mean?
 
(A) Where the President lives.

(B) Direct Current

As opposed to AC which is

(A) Alternating Current

(B) The noisy box on the side of your house that runs when it's hot outside.

Other fun ones -

FM - Frequency Modulation
AM - Amplitude Modulation
RFI - Radio Frequency Interference
BM - Bowel Movement / Bad Mastering :rolleyes:

In software, it's a measure of DC Offset - You want it as close to "nothing" as possible. Say you have a wave - The tops are at 0dBfs and the bottom swing is at -1dBfs. You would have a (negative?) DC offset of 1dB.

Once the DC offset of that wave is corrected, both swings would measure -0.5dBfs.
 
this is kind of related....but what exactly causes the DC offset problem? Is it an issue with the A/D conversion or something else?
 
It can be caused by a bunch of different things. Really old converters used to have this problem (on purpose) but it must be compensated for now. Your preamp or anything else you are running through could have DC leaking into the audio path.
 
:D

DC = "Don't Chill."

"Dumb Choice"

"Dominic Calliastro"

AND,

Dos cervasas es mas major entonces UNA!

Salute`

Vespa Verde :cool: :eek: :D :D
 
Dc?

I'm still not really sure what this is. How does it affect the sound and how do I know when to correct it?
 
If you hit stop at a silent part of audio and you hear a pop, you have DC.

If you zoom in on a silent part of the waveform and see that it is not at 0, you have DC.

If your overall waveform is not centered around the 0 point, you might have DC.

If you are worried about it and have not experienced it, don't know how to detect it, and don't know what it is, don't worry about it. Just make music.
 
DC offset correction

So if I use DC offset correction like in Soundforge it will automatically fix it?
And what if there is no problem but I run the correction anyway?
 
It shouldn't do anything. There are other reasons why the wave might be lop-sided, like heavy compression. You would not want to run it on everything, only when you think you have a problem.
What makes you think you have this problem?
 
I don't know if I have this problem. I just wat to learn about the DC Offset thing.
 
chewie. if you get significant dc offset this sometimes indicates a poor soundcard design. consumer sound cards typically have poor dc offset.
on board sound as well.
so - when your looking at a new sound card take something like forge or even download the old cool edit 96 at the dealers shop (most have net access now) and measure the dc offset of the soundcard your thinking of buying. if it exhibits bad dc offset, look at another sound card.
most decent sound cards these days have immesurable dc offset now.
 
Remember I know nothing.

How would I use those apps to test?
And is DC Offset a property of the card itself or also it has to do with the source?
 
dc offset is a property of the sound card.
read up about it on google.
the dc "rides" on the coattails of the audio waveform.
to test just record some audio, and usually just hilite a blank piece of audio
where a track waveform isnt playing for example and choose the menu option.wherever dc offset is located.
in cool edit if i remember its under an analysis function.
you can also see the dc offset in areas of audio between the
waveforms. look for a line just offset from the horizontal guide line.
i havent used forge in a while. as my multitrack software shows me this.
so just use help in forge..
 
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