AV News 194 - November 2013
Which brings us to option 3.
So what constitutes 'wired in the correct way' and why does that vary
according to intended use? This is the nub of this F.A.Q.
Figure 1 shows a microphone connected via a coaxial screened lead to the
input amplifier of a recording device.
There is a single conductor in the cable which carries the signal, with the
outer screen providing a return path to complete the circuit. The screen is
both a screen and part of the signal path. This 'unbalanced' connection is
typical of cheap and cheerful consumer equipment. Whilst it is simple, it has
drawbacks that are outside the scope of this article.
The arrangement shown in Figure 2 overcomes these drawbacks and is
the standard 'balanced' connection, used in all professional equipment.
There are two conductors in the cable, forming the signal path. The screen
is only a screen and is not connected to the signal path.
As long as you stick to one or the other, all will be well. However in the real
world we serious amateurs tend to be working in the grey area where some
of our equipment will be professional, and some consumer. We need to be
careful.
Nowadays any even half-decent mic will have a balanced output, and will
normally have the male half of a 3 pin XLR connector built into the end of
the handle. (I would regard mics not so configured as probably best
avoided.) A professional recorder/camcorder will also have a 3 pin XLR mic
input connector, and we would connect in the standard Fig 2 manner. Fine
However, many camcorders, and virtually all computer soundcards, have
mini jack mic input connectors - indicative of an unbalanced input. In this
case you need to connect one of the signal leads to the screen, preferably
at the recorder end.
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