Media College (Chương 1 : Âm thanh)(3,4)
Posted by tuyenphuc on 13 Tháng Ba, 2010
Phần 3: Cân bằng trong âm thanh.
This tutorial explains how balanced audio systems work. It is suitable for people who have a basic understanding of audio cables and connectors, as well as simple wave interactions (such as how waves from different sources interfere with each other). If you don’t understand these things, take our introduction to audio tutorial first.
What is Balanced Audio?
Balanced audio is a method of minimizing unwanted noise from interference in audio cables. The idea is that any interference picked up in a balanced cable is eliminated at the point where the cable plugs into a sound mixer or other equipment.
Balanced audio works on the principle that two identical signals which are inverted 180° out of phase will cancel each other out. The cables used in such systems are designed to carry two versions of the signal and manipulate the relative phases of these signals to eliminate noise.
This will make more sense when we look at how balanced cables work, but first we need to take a step backwards and look at unbalanced audio cables.
Unbalanced Audio Cables
Traditional unbalanced cables use two lines to transmit the audio signal – a hot line which carries the signal and an earth line. This is all that is required to transmit audio and is common in short cables (where noise is less of a problem) and less professional applications.
Unbalanced Audio Connectors
Unbalanced audio cables are commonly associated with the 1/4″ phono jack connector and the RCA connector. However any single-pin connector used for audio is unbalanced. 3-pin XLRs can also be used for unbalanced cables. For more information about these connectors, including how to wire them, see Audio Connections.
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