Varying DC offsets in recording

This may or may not be an ER-301 specific question, but since it’s my main recording equipment it seems ok to ask this here. I have DC offsets that vary inexplicably (for me at least) during a recording session. This particular session uses some sample players, clocked delay, + an external sound source. It just goes up and down, sometimes abrupt, sometimes gradually. Any clues on how to avoid this, why it happens, and also how to fix it when it happens? I’ve been doing some parts by hand in Audacity but it’s very tedious.

Determine where the DC offset is coming from and put a Fixed HPF unit after it. All of the inputs on the ER-301 are DC-coupled so if your external sound source has any DC offset it will be captured unaltered inside the ER-301.

Another possibility is the way the Sample Player prevents clicks when discontinously moving the play head from one location in the sample buffer to another is to preserve the DC offset from the previous play head position and slowly fade the DC component out. The length of this fade is controlled by the ‘fade’ parameter. So make sure it is not too long, usually 5-10ms is enough. Since there is no time scale on your pictures I couldn’t tell if this was an issue so I’m just mentioning it just in case.

Or, if you are feeling lazy and don’t have the time to figure out where the DC offset is coming from, just put a Fixed HPF unit at the end of your OUTx chains.


Cool, thanks. Will check all of that and try the HPF. These are my first recording sessions where I actually start mixing and analyzing the waveforms so I haven’t taken any precaution. (I wonder if my Mangrove could have a DC offset…? I’ll check)

Oh and by the way, Audacity has a High Pass Filter (HPF) also. Just select the entire recording, Effect > High Pass Filter and use a cutoff frequency of around 20Hz.

Great! I think I may even have found the culprit already: when mixing in the wet signal from my Jellyfish delay (Plankton Electronics), it clearly dips down below the zero point.

By the way, this HPF is magic. So happy I posted here and didn’t first do this by hand for like, the entire weekend.


I wouldn’t be too surprised. Analog synthesis is peppered with DC offsets everywhere. It’s part of the territory.

Noob question here: what’s the concern with DC offsets exactly? I’ve noticed on some of my recordings, even prior to the 301, had waveforms that were “off centre” but to my ear sounded fine, maybe a little phase-y. Why exactly is this bad on the audio side of things?

Noob answer here: one thing I can think of is clipping. If your recording has offsets both below and above the zero point, then you will need way more headroom to avoid clipping. And then mixing audio signals with different offsets somehow feels weird, but that’s as technical as I will get :smiley:

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