Yamaha MC2410M - Manual (Page 12)

INSTALLATION
IMPORTANT!
* This unit is designed to operate within + 10% of rated
voitage. Aithough, even if the power supply voltage
drops by up to -30%, the unit can still be used without an
increase in hum noise, but the maximum ouput level will
be reduced.
* Ideally, this unit should be used in a dust-free environ­
ment, with low humidity. Do not install them near heat­
ers, or near equipment that causes noise or hum.
HOOK-UP CABLES AND HUM AVOIDANCE
The MC mixing console's primary inputs and outputs fea­
ture electronically balanced circuits and connectors. When
these connectors are used with the appropriate 2-conductor
shielded cables (e.g. standard microphone cables) these cir­
cuits provide optimum protection against hum and noise
pickup. The XLR type connectors are wired with pin 2 as
"audio high" and pin 3 as "audio low", in accordance with
DIN and lEC standards. In the balanced TRS connectors, the
tip is audio high and the ring is audio low. Pin 1 in the XLR
type connectors, and the sleeve in the TRS connectors are
ground.
Some professional audio equipment and microphones are
wired with pins 2 and 3 (XLR) reversed. Generally, this will
cause no problem other than a polarity reversal. However, if
such a piece of equipment uses a balanced-type connector
for an unbalanced input, or an adaptor is used to match an
unbalanced connector to a balanced input, the high side of
the audio circuit could be grounded. In this case, reverse
the audio high and audio low wiring at one end of the con­
necting cable, or use a suitable polarity-reversal adaptor.
Regardless of connector polarity, if hum is encountered try
cutting the shield connection at one end of the cable.
All unbalanced phone jacks are intended for use with stan­
dard tip-sleeve 1/4" phone plugs and single-conductor
shielded cable. Do not attempt to reduce hum by cutting the
shield connection on these cables. Rather, restrict unbal­
anced cables to about 3 meters (10 feet), and try to set up
the system so that the equipment involved is all connected
to the same AC circuit.
IMPORTANT; Breaking the ground path can create a SHOCK
HAZARD. When routing cables, especially unbalanced
cables, avoid strong sources of electro-magnetic interfer­
ence or radio frequency interference generated by electric
motors, fluorescent lights, dimmer panels, etc. To avoid
crosstalk-induced feedback, never bundle microphone
cables with mixing console output cables: these cables
should cross at right angles where practical.
GROUNDING
Careful grounding procedures are essential for proper oper­
ation, not only of the mixing console, but of the entire audio
system. Many grounding techniques exist, and a number of
books have been written on the subject. The following are
good sources of information on grounding and related sub­
jects.
THE AUDIO CYCLOPEDIA by Howard M. Tremaine
(Pub. Howard W. Sams)
SOUND SYSTEM ENGINEERING by Don and Carolyn Davis
(Pub. Howard W. Sams)
GROUNDING AND SHIELDING IN INSTRUMENTATION
by Ralph Morrison
(Pub. John Wiley & Sons)
SOUND REINFORCEMENT HANDBOOK by Gary Davis and
Ralph Jones
(Pub. Hal Leonard Pub.)
"Ground loops" are often caused by multiple paths from
the equipment grounds to the AC mains ground (or earth
ground). Ground loops are a major cause of hum and noise
in an audio system. In severe cases, ground loops can even
cause the equipment involved to break into oscillation. This
can cause distortion and even damage to amplifiers and
speakers. One way to avoid ground loops is to make sure
that there is only one path to the AC ground of the entire
audio system. A popular method is to cut the shield ground
of balanced cables at the input end of the cable. Another
technique is to ground all shields at one piece of equip­
ment, typically the console, and cut the shields at the other
ends of the cables.
(Note: this is NOT possible with unbalanced cables).
CHECK MAINS VOLTAGES
Connect the mixing console to the AC mains only after con­
firming that the line voltage and frequency are correct. A
simple check with a voltmeter can save your equipment -
and the show. It is also a good idea to check for proper
polarity at the AC outlet. The power switch on the console
should be OFF before connection to the mains. As a further
precaution, disconnect the console from the mains while
audio cables are being installed.
MATCHING INPUT CHANNEL SENSITIVITY TO THE
SOURCE
The pad switch and gain control on each input channel per­
mit adjustment of the input sensitivity between -60 dB and
+4 dB. With the pad out, the gain control has a sensitivity
range of -60 dB to -16 dB. With the pad in, this range is
-40 dB to +4 dB. This makes it possible to match the input
sensitivity to a broad range of input sources.
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