Bias points in an amp are important. The bias point of the last preamp stage is the most important. Therefore Quantum firmware exposes this bias point on the Pre Dyn tab as the Preamp Bias parameter. Most amps are biased slightly towards cutoff (negative). The closer you get to 0.0 the more odd harmonics and the fewer even harmonics. Experiment with this to craft your "Ultimate Tone" (TM, all rights reserved, use only as directed, these statements have not been evaluated by the FDA).