Yamaha EMX312SC Owner's Manual - Page 14
Balanced, Unbalanced—What’s the Difference?, How Do Balanced Lines, Reject Noise? - powered mixer with effects
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BASIC Making the Most of Your Mixer type connectors will also handle unbalanced signals with no problem. Microphone cables usually have this type of connector, as do the inputs and outputs of most professional audio gear. Balanced, Unbalanced-What's the Difference? In a word: "noise." The whole point of balanced lines is noise rejection, and it's something they're very good at. Any length of wire will act as an antenna to pick up the random electromagnetic radiation we're constantly surrounded by: radio and TV signals as well as spurious electromagnetic noise generated by power lines, motors, electric appliances, computer monitors, and a variety of other sources. The longer the wire, the more noise it is likely to pick up. That's why balanced lines are the best choice for long cable runs. If your "studio" is basically confined to your desktop and all connections are no more than a meter or two in length, then unbalanced lines are fine-unless you're surrounded by extremely high levels of electromagnetic noise. Another place balanced lines are almost always used is in microphone cables. The reason for this is that the output signal from most microphones is very small, so even a tiny amount of noise will be relatively large, and will be amplified to an alarming Balanced noise cancellation Noise Hot (+) Cold (-) Ground Source Cable degree in the mixer's high-gain head amplifier. How Do Balanced Lines Reject Noise? ** Skip this section if technical details make you queasy. ** Balanced lines work on the principle of "phase cancellation": if you add two identical signals out of phase (i.e. one signal is inverted so its peaks coincide with the troughs in the other signal), the result is ... nothing. A flat line. The signals cancel each other out. A balanced cable has three conductors: 1) A ground conductor which carries no signal, just the "ground" or "0" reference against which the signal in the other conductors fluctuates. To summarize Microphones: Use balanced lines. Short line-level runs: Unbalanced lines are fine if you're in a relatively noise-free environment. Long line-level runs: The ambient electromagnetic noise level will be the ultimate deciding factor, but balanced is best. Noise-free signal Phase inversion Noise cancelled Receiving device 2) A "hot" or "+" conductor which carries the normal-phase audio signal. 3) A "cold" or "-" conductor which carries the reverse-phase audio signal. Balanced Hot Unbalanced Cold Shield (Ground) Outer Insulation While the desired audio signals in the hot and cold conductors are out of phase, any noise induced in the line will be exactly the same in both conductors, and thus in phase. The trick is that the phase of one signal is reversed at the receiving end of the line so that the desired audio signals become in-phase, and the induced noise suddenly finds itself out of phase. The out-of-phase noise signal is effectively canceled while the audio signal is left intact. Clever, eh? 14 EMX512SC/EMX312SC/EMX212S