AC, or alternating current, is electrical current or voltage that periodically reverses direction, in contrast to direct current (DC), which flows in one direction only. In a synthesizer, AC is usually associated with audio signals, because they swing above and below a zero point in the same way alternating current does.
Characteristics of AC in synthesizers
- Signal behavior: AC signals in a synthesizer are the audio itself. Their voltage fluctuations create sound waves, with amplitude heard as loudness and frequency heard as pitch.
- Audio processing: Most audio equipment and synthesizer modules are built to handle AC signals. Amplification, filtering, modulation, and effects are mostly applied to AC signals to shape the sound.
- Isolation from DC: It is often important to keep AC audio separate from any DC voltage, because DC can introduce noise, offset, and other unwanted effects. Capacitors and AC coupling settings on mixers and interfaces do this, so only the alternating part of the signal is processed.
