Hüllkurventeiler

Hüllkurventeiler, often translated as envelope follower or contour generator, is an electronic circuit commonly found in synthesizers and audio effects processors. Its primary function is to track the amplitude envelope of an incoming audio signal and use this information to control a parameter of another circuit. Essentially, it "listens" to how loud a sound is and then uses that loudness to shape another aspect of the sound.

The core principle involves analyzing the peaks or overall loudness of an input signal. This analysis can be done in various ways, often involving rectification and smoothing. Rectification converts the alternating current (AC) audio signal into a pulsating direct current (DC) signal, where all the negative portions are flipped to be positive. Smoothing then averages out these pulsations, producing a relatively steady DC voltage that represents the signal's instantaneous amplitude.

This derived DC voltage, known as the envelope signal, can then be routed to control various parameters. Common applications include controlling the voltage-controlled amplifier (VCA) to shape the loudness contour of a synthesized sound (attack, decay, sustain, release), or modulating the cutoff frequency of a voltage-controlled filter (VCF) to create dynamic timbral changes. More advanced hüllkurventeiler circuits might offer adjustable attack and decay times, allowing for precise shaping of the envelope. In essence, a hüllkurventeiler translates the dynamic behavior of one audio signal into a control signal that dynamically alters another audio characteristic.