An even-order harmonics control technique for analog pedal effector

摘要

The primary distortion mechanism of the analog guitar pedal effector is saturating nonlinearity of a transfer function, which consists of operational amplifier and diode clippers with filters. The output spectrum of this system shows odd-order harmonics primarily, but it also contains even-order harmonics. We found that the intensity of this even-order harmonic varies depending on the power supply voltage, and clarified the mechanism by analysis of the internal circuit topology of the operational amplifier. The analysis was justified compared with the conventional single-ended transistor pedal operation. Based on the analysis, we proposed a new concept of even harmonic control technique, which was applied for analog "Distortion" pedals and demonstrated distinguished experimental results with a prototype.