I found a rather interesting video demonstrating the advanced amp parameters of the Line 6 Helix: sag, hum, ripple, bias and bias-x. As a summary, this is what I could infer to them:
- sag – lower is tighter and less dynamics; higher sounds muffled;
- hum – the literal ground hum of the amp;
- ripple – harmonic undertone audible on single notes; hard to hear in a mix;
- bias and bias-x – changes the overdrive character when used together.
Basically, these parameters make close to zero difference in clean tones. Crunch and high gain tones can change in thousands of ways, though.
Back to the tone chasing.