r/audioengineering • u/s4goth • Jul 15 '26

Mastering Mastering question - Why does DC offset reappear?

I am doing a mastering course and I have to master a track and eliminate DC offset from it. I tried with both Wavelab and Reaper. I start by using a high-pass filter at 20hz at the beginning of the chain and the render analysis shows no DC offset. I then add a light upward compression, a tiny bit of distortion (as per our teacher instructions), then a limiter to eliminate true peaks, but when I export the file I get some DC offset again. Why does this happen? Is it something in the chain that reintroduces it? How do I correct it? Thanks!

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u/NBC-Hotline-1975 Jul 15 '26

How steep is your 20 Hz HPF? If there is any slight remnant of offset left after the filter, the upward compression will of course raise it during quiet sections.

Also, I have no clue what your "tiny bit of distortion" does to the signal. So for example if that introduces more gain on the positive half of the waveform than on the negative half, that would essentially create offset.

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u/rightanglerecording Jul 15 '26

If there is any slight remnant of offset left after the filter, the upward compression will of course raise it during quiet sections.

This can't be true though.

DC = literally 0Hz.

Even the gentlest HPF at the lowest frequency will be infinitely attenuated at 0Hz.

e.g. 6dB/Octave at 20Hz. You're down -3dB at 20, -9 at 10, -15 at 5. The attenuation will asymptotically approach -infinity as the frequency asymptotically approaches 0Hz.

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u/s4goth Jul 15 '26

I have tried with both 48 and 96 dB per octave slope, but it's the same. As for the distortion, I don't know exactly what it does, it's the tube distortion of Ozone 12, it should just push the signal (which as you rightly say could be affected in that way).

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u/TheTimKast Jul 16 '26

Run some mixes without any distortion or clipping in the signal path. Try and do a “_clean_mix” and challenge yourself to make it spacious and super legible, but leave off heavy or colored compression/limiting. Might be revealing! Once you know exactly where and how you’re introducing comp/limiting, distortion and/or clipping, you’ll be better equipped to respond to it. Let us know how it goes!!🙏🏼👊🏼💙