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For the best results and the satisfaction from your new unit, please read
this manualthoroughly, and retain it for future reference.
Balanced, Unbalanced-What's the Dierence?
In a word: "noise." The whole point of balanced lines is noise rejection, and its
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 conned to your desktop and all connections are no more than a meter
or two in length, then unbalanced lines are ne-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 amplied to an alarming degree in the
mixer's high-gain head amplier.
Balanced Noise Cancellation
Signal Levels and the Decibel
Let's take a look at one of the most commonly used units in audio: the decibel
(dB). If the smallest sound that can be heard by the human ear is given an
arbitrary value of 1, then the loudest sound that can be heard is approximately
1,000,000 (one million) times louder.
That's too many digits to deal with for practical calculations, and so the more
appropriate "decibel" (dB) unit was created for sound-related measurements.
In this system the dierence between the softest and loudest sounds that can
be heard is 120 dB. This is a non-linear scale, and a dierence of 3 dB actually
results in a doubling or halving of the loudness.
You might encounter a number of dierent varieties of the dB: dBu, dBV,dBM
and others, but the dBu is the basic decibel unit. In the case of dBu, "0 dBu" is
specied as a signal level of 0.775 volts. For example, if a microphone's output
level is -40 dBu (0.00775 V), then to raise that level to 0 dBu (0.775 V) in the
mixer's preamp stage requires that the signal be amplied by 100 times. A mixer
may be required to handle signals at a wide range of levels, and it is necessary
match input and output levels as closely as possible. In most cases the ''nominal"
level for a mixer's input and outputs is marked on the panelor listed in the
owner's manual.
Most professional mixers, power ampliers, and
other types of equipment have inputs and outputs
with a nominal level of +4 dBu
The Inputs and outputs on home-use audio gear
usually have a nominal level of -7.8 dBu (-10 dBV).
Microphone signal levels vary over a wide range
depending on the type of microphone and the
source. Avarage speech is about -30 dBu, but the
twittering of a bird might be lower than -50dBu
while a solid bass drum beat might produce a
level as high as 0 dBu
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