Hi unholyernest,
So I understand that you are not clipping at the recording stage, i.e. the signal your audio interface is receiving is not too high. But, your waveform that "looks like a BLACK CHUNK" definitely resembles digital clipping. I don't know for sure without looking at the waveform closely, but digital clipping can occur in digital multi-effects board and is actually a very common phenomenon.
Remember, if you are using a digital pedal, it can clip within the pedal too. What a digital pedal does is:
1) Convert your guitar into Digital
2) Add effects
3) Convert back to analog and output to 1/4" main output (some multi-effects board have digital output too, via USB or SPDIF etc... so this stage may be skipped)
It acts like a "mini" computer with a soundcard (A-D and D-A stages), so clipping is a definite possibility. To check for clipping within the digital effects board, zoom in your recorded waveform and observe the peaks. If they look flat, and your effects is not a square-wave type fuzz, it is most likely clipping within the effects board.
Try to observe for both clean and distorted waves. If it clips even in clean, you simply need to lower your guitar volume.
If it clips only in distortion, you need to:
1) Check that you don't have too much pre-gain.
2) Check that you don't have too much post-gain.
Remember that both pre and post-gain can bring the signal beyond clipping point.
One very common problem with guitarists using digital effects is that they tend to add too much pre-gain in order to achieve higher levels of distortion. You can't afford to do that in the digital domain because digital signals don't "clip in a nice-sounding way". If you need higher distortion, add more drive (compression) to the signal, and lower the pre-gain.
Hope I helped!
