Crinkle introduces noisy artifacts on the repeats that I like to describe as “dusty” (see the Fairy Dusty preset). It’s more apparent when the tape age is set to the right. Bias on the other hand is how sound is put on the tape. If it’s underbiased there will be dropouts after a few repeats around the zero-crossing point (crossover/zero-crossing distortion) or in the softer part of the wet signal (see the Unbiased Opinion preset). If you overbias, the sound will be pushed more into a soft-clipping circuit that can introduce some overdrive (see Mulholland Drive). I hope this clarified things! If not don’t hesitate to ask.
