KVR Audio

Debutante · Post by **Debutante** » Sat Apr 09, 2005 2:18 pm

Hello again you geniuses...I know this topic must have been discussed before but I searched the site and didn't really find something in the archive (please point to a previous discussion if you know of) but I am beginning to understand that DC OFFSET doesn't come in a single flavour....can someone please elaborate on some different treatment methods ,because a simple plugin sometimes doesn't work effectively enough...CHEERS!

Sicklecell666 · Post by **Sicklecell666** » Sat Apr 09, 2005 2:34 pm

There's more than one way of eliminating it. Most people use a High pass filter, which is the method employed I believe in Audition & works for me well enough. If you have Reaktor, I have a macro that works as well.

IIRs · Post by **IIRs** » Sat Apr 09, 2005 2:42 pm

Sicklecell666 wrote: Most people use an all pass filter,

Don't you mean a high-pass filter?

Think of DC offset as a sine wave with a very low frequency.. any high-pass filter should remove it, even with a cutoff frequency set at 10Hz or lower..

If you're processing off-line however (eg: in an audio editor) you might find it will analyse the audio for average levels, and simply scale the whole waveform up or down..

Sicklecell666 · Post by **Sicklecell666** » Sat Apr 09, 2005 2:51 pm

platinumears wrote:
Sicklecell666 wrote: Most people use an all pass filter,
Don't you mean a high-pass filter?

That's one way. Another is to insert an allpass filter with a low cutoff-freq.

We had a discussion about it in the Reaktor forum, but I can't past the actual page for some reason; NI doesn't hotlink for me at all..

edit: but you're right: most people use HIGH pass for fixing. It was someone else that suggested all pass as an alternative. Coffee ain't sunk in yet..

Debutante · Post by **Debutante** » Sat Apr 09, 2005 2:57 pm

...thanks alot people....I didn't even know what this annoying occurence was. i'll try this my new filtering trick!

Sicklecell666 · Post by **Sicklecell666** » Sat Apr 09, 2005 2:57 pm

platinumears wrote:If you're processing off-line however (eg: in an audio editor) you might find it will analyse the audio for average levels, and simply scale the whole waveform up or down..

So are you recommending it NOT be repaired offline, then?

rockstarfx · Post by **rockstarfx** » Sat Apr 09, 2005 3:14 pm

dc offset pisses me off >:O

ObsoleteAcc99 · Post by **ObsoleteAcc99** » Sat Apr 09, 2005 3:17 pm

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IIRs · Post by **IIRs** » Sat Apr 09, 2005 3:55 pm

Sicklecell666 wrote:
platinumears wrote:If you're processing off-line however (eg: in an audio editor) you might find it will analyse the audio for average levels, and simply scale the whole waveform up or down..
So are you recommending it NOT be repaired offline, then?

It depends: reparing it off-line with a simple scaling algo is guaranteed not to change the audio in any way other than to remove the off-set (eg: phase will not be altered at any frequency).. otoh many signals benefit from being high-pass filtered in the mix anyway, in which case it will simply take care of itself.

Sicklecell666 · Post by **Sicklecell666** » Sat Apr 09, 2005 4:00 pm

Gotcha, thanks! I don't tend to use High passes in the final mix, but I guess I should anyways to roll off the heavy stuff that muds me up on the bottom end..

Rellik · Post by **Rellik** » Sat Apr 09, 2005 9:31 pm

ANY hi-pass filter will remove DC offset, no matter how low the cutoff is set.

Removal of DC offset should happen anytime the signal is going to be fed through a push-pull pair of transistors - so before the final output. Since mixing of signals is additive, the DC offset will be added up until you get to the final mix, so any and all constant DC offset should be removable there. However, DC offset can cause clipping on one side of the signal if it's extreme, so it's best to remove it anywhere it shows up, to preserve the purity of the signal.

EDIT: and could someone tell me what an all-pass filter is? If it's what it sounds like, then

, but I know from Antti's ASynth that it has a cut-off frequency, and it actually does affect the audio signal - so I'm really curious now.

IIRs · Post by **IIRs** » Sun Apr 10, 2005 12:52 am

Rellik wrote: EDIT: and could someone tell me what an all-pass filter is? If it's what it sounds like, then , but I know from Antti's ASynth that it has a cut-off frequency, and it actually does affect the audio signal - so I'm really curious now.

All-pass filters pass all frequencies, but change the phase of those at or near the cutoff. (Think of it as a short frequency specific delay if you like.) Adding the output of an all-pass back to the original signal will produce cancelation at the cutoff freq, and this technique is the basis behind phaser effects.

Panda · Post by **Panda** » Sun Apr 10, 2005 8:07 am

Rellik wrote:Removal of DC offset should happen anytime the signal is going to be fed through a push-pull pair of transistors - so before the final output.

What exactly is a push-pull pair of transistors?

stefancrs · Post by **stefancrs** » Sun Apr 10, 2005 8:11 am

ttoz wrote:when should it be applied? to every audio file recorded right? and to the final master? what about after vsti outputs?

Depends. I tend to dislike synths that produce DC offset.

Apart from that, I can't remember ever having a problem with it. I always use highpass filtering on the master and also on most of my other tracks. Usually before a compressor.

ObsoleteAcc99 · Post by **ObsoleteAcc99** » Sun Apr 10, 2005 10:50 am

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DC Offset