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IMPORTANT!
* This unit is designed to operate within +/— 10% of rated
voltage.
`
* Ideally, these units should be used in a dust-free environ-
ment, with low humidity. Do not install them near heaters,
or near equipment that causes noise or hum.
:
* After you have finished reading this manual, be sure to
store it in a safe place, together with the guarantee certifi-
cate.
AC POWER CONNECTION
(for models with 3-wire power cable)
Mixing consoles provided with a 3-wire power cable should
be AC grounded for safety and optimum shielding against
noise. If a 3-wire AC outlet is not available, or there is any
chance that the AC outlet is not grounded, a separate ground
wire must be connected from the console chassis to an earth
ground. Cold water pipes generally provide a good ground,
unless they are insulated by PVC plastic, or are fitted with a
water meter. Avoid hot water pipes and gas pipes.
When a convenient, confirmed ground is not available, use a
length of copper
pipe driven into moist, salted earth to a
depth of at least 1.5 meters (5 feet). Alternatively, use a
chemical type grounding rod.
HOOK-UP CABLES AND HUM AVOIDANCE
The
MC
monitor
mixing
console's
primary
inputs
and
outputs
feature
electronically
balanced
circuits
ала
connectors.
When
these
connectors
are
used
with
the
appropriate 2-conductor shielded cables (e.g. standard micro-
phone
cables)
these
circuits
provide
optimum
protection
against hum and noise pickup. The XLR type connectors are
wired with ріп 2 as "audio high" and pin 3 as "audio low",
on accordance with DIN and JIS standards. In the balanced
TRS connectors, the tip is audio high and the ring is audio
low. Pin 1 in the XLR 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 connecting
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
standard 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 unbalanc-
ed cables to about 3 meters (10 feet), and try to set up the
system
so that
either (a) the equipment
involved is all
connected to the same AC circuit, or (b) the third-wire AC
mains
ground
is used
on
only one
piece of equipment,
typically the mixing console.
'IMPORTANT:
Breaking
the
ground
path
can
create
a
SHOCK
HAZARD.
When
routing
cables,
especially
ип-
balanced
cables, avoid strong sources of electro-magnetic
interference
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
operation, not only of the monitor 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 subjects.
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)
"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. [n 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 or the entire audio system.
А 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 equipment, 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
confirming 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.
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