SoundCraft SPIRIT POWERSTATION, Руководство пользователя

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Balanced and Unbalanced
All channel inputs are balanced, i.e. there are separate
+ve(hot) and -ve (cold) wires for each signal plus a ground.
The design of the differential input amplifiers is such that
interference picked up on these wires is cancelled out. This is
because, since both wires are in close proximity, the same
interference will be picked up on each wire and balanced
input amplifiers will only amplify the difference between
+ve(hot) and -ve(cold). Any signal on both hot and cold (i.e.
noise) will not be amplified - this is known as common mode
rejection (CMR). Balanced inputs should always have both
+ve and -ve connected or if only an unbalanced source, the
-ve pin shorted to ground.
Note: many modern audio/musical instruments have
electronically balanced outputs which should not be
unbalanced by shorting one wire to ground. Always use your
inputs balanced where possible to minimise noise.
The Mixer and Graphic Equaliser outputs are all impedance
balanced and provide a very effective way of optimising noise
immunity, without the cost and complexity of balanced
outputs (note: This is the method used in most condenser
mics)
Polarity
You will probably be familiar with the concept of polarity in
electrical signals and this is of particular importance to
balanced audio signals. Just as a balanced signal is highly
effective at cancelling out unwanted interference, so two
microphones picking up the same signal can cancel out, or
cause serious degradation of the signal if one of the cables has
the +ve and -ve wires reversed. This phase reversal can be a
real problem when microphones are close together and you
should therefore take care always to connect pins correctly
when wiring audio cables.
Grounding and Shielding
For optimum performance it is vital that all signals are
referenced to a solid, noise-free earthing point and that all
signal cables have their screens connected to ground. You
should be aware that you may introduce ground loops with
screens connected to ground at both ends of a cable, and it
may be necessary to lift the ground at one end to avoid this
problem. Note that microphones must always be grounded.
The
SPIRIT POWERSTATION
should be used as the
grounding point for the system, and an earth stud is provided
beside the power connector.
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