autowah

Autowah, also known as auto-filter or envelope filter, is an effects pedal that creates a sweeping filter sound. Unlike a traditional wah pedal that requires manual foot control, the autowah uses an envelope follower to detect the dynamics of the input signal. The loudness of the note played directly controls the cutoff frequency of a resonant filter, causing the filter to sweep up or down in response to the playing intensity.

The core of an autowah effect is a resonant low-pass filter. When a note is played loudly, the envelope follower detects this and sends a control voltage to the filter. This control voltage raises the filter's cutoff frequency, allowing more high frequencies to pass through and creating a brighter, more open sound. As the note decays or is played more softly, the control voltage decreases, lowering the cutoff frequency and resulting in a darker, more muted sound. This dynamic interaction between the input signal and the filter creates the characteristic "quack" or "wah" sound.

Autowah pedals offer several controls to shape the effect. Typically, there are controls for sensitivity or threshold, which determines how much the input signal's dynamics affect the filter. A resonance control adjusts the intensity of the filter's peak, making the sweep more pronounced. Often, there are also controls for attack and decay, influencing how quickly the filter sweeps up and down. Some units also offer modes that invert the filter's response, sweeping downwards in frequency instead of upwards. Autowah is commonly used by bassists and guitarists in funk, jazz, and other genres to add rhythmic texture and expressive modulation to their sound.