Amplifier Distortion + Amplifier Feedback

Distorted Electric Guitar with Amplifier Feedback

• Distortion can be preceded and followed by EQ
  E.g., integrator ``pre'' and differentiator ``post''

• Distortion output signal often further filtered by an amplifier cabinet filter, representing speaker cabinet, driver responses, etc.

• In Class A tube amplifiers, there should be duty-cycle modulation as a function of signal level¹
  • 50% at low levels (no duty-cycle modulation)
  • 55-65% duty cycle observed at high levels
    $\Rightarrow$ even harmonics come in
  • Example: Distortion input can offset by a constant
    (e.g., input RMS level times some scaling)