Voltage Controlled Amplifier Explained

This entry aims to explain how a voltage controlled amplifier works. It is a device that can modify the amplitude of a signal. This device involves two types of inputs: the carrier and the modulator. The carrier, also known as the signal input, is where the bipolar input comes in. The modulator, also known as the control input, is where a uni-polar positive signal comes in.

Voltage Controlled Amplifier: How It Works

The voltage-controlled amplifier receives a bipolar signal at its carrier and a uni-polar positive signal at its modulator. The output signal is the result of the combination of these two signals. In other words, it is the multiplication of both amplitudes within the same period of time. Many voltage-controlled amps involve gain knobs that are capable of setting different values. 

A carrier signal can only pass through a voltage-controlled amp if a positive signal passes through the control input or if a positive bias is provided. When the signal is biased to zero and there is no modulation signal present, no signal will be received at the output. Because of this, a uni-polar positive signal is typically provided to the control input. It sends a bipolar signal when the sound changes because of certain effects.

Voltage Controlled Amplifier: Its Uses

Voltage-controlled amplifiers have many uses, such as envelope shaping, tremolo, amplitude modulation, and volume control.

Envelope Shaping

First, envelope shaping is the resulting effect of the player hitting a note on an electronic instrument. The consequence is the generation of an attack and a slow delay. This effect provides emotion and a natural quality to any given sound. The process of envelope shaping requires both a VCA and an envelope generator. This envelope generator has four parameters: attack, decay, sustain, and decay. The procedure is quite simple: an audio signal passes through the input signal of the VCA while the control input receives the signal from the envelope generator.


Second, the tremolo effect occurs if the frequency of the modulator is low and intermittent volume changes to the audio signal happen. In other words, tremolo refers to as a smooth and slow effect that generates a repeating change in loudness.

Amplitude Modulation

Third, amplitude modulation occurs if the frequency of the modulator is so fast that the shape of the original audio signal changes. As a result, you get the production of completely different sounds and pitches.

Volume Control

Fourth and last, voltage-controlled amps are capable of regulating the volume of any given sound. The process is simple. The audio signal passes through the signal input and connects the control input to the mod wheel or the foot pedal.