DC Offset: Clicks and Pops

Robert Katz Leave a Comment

Well, I really was thinking something along the lines of, exactly is the
theory behind it? I know that dc is 0 hertz, and I know that dc
offset is when the soundfile is not centered around the baseline of the
waveform.

You’re correct! The way I determine if the DC offset is severe enough to have to deal with is if you hear a click or pop when starting or stopping the material during a soft passage. If you don’t then I would say ignore it as the cure can be worse than the disease.

What is the prefferred method for adjusting DC offset?

Very rarely is DC offset a problem in the first place. So I think the most successful and transparent method is not to do anything! However, if you have a DC offset problem that’s large enough to cause an audible pop when you start and stop the material, then the most successful methods I’ve used have been to apply an extremely-high quality linear phase high pass filter. Why linear phase? Because to my ears, the phase shift of a severely-applied minimum phase (standard variety) high pass filter is audible. Same as a capacitor in series in an analog output circuit can be heard by keen ears with a good monitoring system.

In order of preference, the best unit I have had for this is the 13.8 Hz high pass filter in the Weiss EQ1-Mk2 (in linear phase mode). Assuming that there is no extra low frequency information in the material that we want to keep (and sometimes there is, even at 13.8 Hz). The second most successful has been the high pass filter in the Algorithmix Red and the only reason it has been less successful than the Weiss is (currently) the Alg. red starts at 20 Hz; though it can be made steep, it sometimes eats into important low frequency information we want to keep (though this is not usually a problem).  Lastly, in Sequoia, the new FFT filter does a good job at this as well.

Hope this helps

Bob

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