Different types of audio signal
Introduction
It is useful to have a conceptual idea of the different types of audio signals in a recording studio. Many people are confused about the difference between a digital (computer) pulse wave signal and the audio pulse wave signal that a synthesiser's oscillator (for example) can generate.
This article outlines the 6 primary audio signal types.
NOTE: The diagrams shown on this page are simplified waveform diagrams.
Pulse waves
Digital audio signals ...
... are very quiet to allow them to move quickly between computer components and create as little heat, through friction (resistance) as possible. They are pulse waves, employing rising and falling amplitude to represent 1s and 0s.
SMPTE signals ...
... are created digitally inside a SMPTE generator device and then amplified (modulated) to the level of an audio line level signal in order to be recorded onto audio tape. (Old computer games employed the same system to load and save data to cassette recorders when disc drives were still too expensive for consumers).
Audio / line level pulse waves ...
... can be created by a synthesisers oscillators and used as an effective sound source to create such sounds as pianos and basses.
Mic level
Mic level signals are created by microphones, electric guitars and electric bass guitars, and record decks. They are quiet and need the protection of a balanced cable. When they reach a mixer or hi-fi amp, they are amplified to line level by a pre-amp.
Line level
Line level signals are loud and robust and do not always need the protection of a balanced cable.
Speaker level
Speaker level signals are very loud in order to power the magnets which move the cones.
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