A “balanced modulator” is a module or a function within a module that multiplies two input signals, usually an audio signal (also known as the carrier) and a modulation signal (also known as the modulator). The balanced modulator is a key component in various synthesis techniques, most notably amplitude modulation (AM) and ring modulation (RM).
The term “balanced” in this context refers to the fact that the output signal of a balanced modulator does not contain any of the original input signals. Instead, it produces the sum and difference of the input signals’ frequencies, resulting in a complex and harmonically rich output signal. This process generates new sidebands (sum and difference frequencies) while suppressing the original carrier and modulator frequencies.
Balanced modulators are commonly used in modular synthesizers to create a wide variety of timbres and effects, such as metallic or bell-like sounds, dissonant textures, and complex evolving timbres. They can also be used for audio-rate modulation of other parameters, such as filter cutoff frequencies or oscillator pitch.
In a modular patch, a balanced modulator might be used in the following way:
- An audio signal from an oscillator or other sound source is connected to the carrier input of the balanced modulator module.
- A modulation signal, which could be another audio signal, an LFO, or a control voltage from a sequencer, is connected to the modulator input of the balanced modulator module.
- The output of the balanced modulator module is then connected to other modules in the synthesizer, such as filters, effects, or the final output.
By adjusting the input levels and the frequencies of the carrier and modulator signals, a musician can explore a vast range of sonic possibilities, creating unique and distinctive sounds.