Start-Up - Behringer EURODESK SX4882 User Manual

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EURODESK SX4882 User Manual
It is positively undesirable to use screened cable to wire an amp to a speaker.
Speaker leads should be as thick and short as possible, with XLR or wound
post terminals.) Line-level signals can usually be run unbalanced over short
or moderate distances (rack to desk etc.), but NOT from the back of the hall
to the stage, always provided that there are no earth loops (see section 8.3
"Looming problems" A loop acts as an aerial, positively inviting electromagnetic
radiation to flow around the system). Microphone lines, however, are another
story altogether.
Most microphones generate not volts, but millivolts. Protecting such a low
level signal requires a more sophisticated solution. Hence, all mic networks run
along balanced lines. It works like this. The mic diaphragm moves forwards and
backwards according to the air pressure increases and decreases that constitute
sound waves. Diaphragm movement generates a corresponding electrical
signal, which is either positive or negative depending on the direction of travel.
The +ve and -ve signals are mirror images of each other: if you shorted + and -
you'd end up with nothing: one would cancel out the other. In fact this cancelling
effect is what makes the balanced line work. Instead of simply shorting the
negative line to earth, as would be the case in an unbalanced system (losing half
the signal, or 6 dB, in the process), the two lines are kept apart until they reach an
electronic (or transformer) balanced input.
Here something exquisitely simple happens:
You may not know this, but whenever a signal is amplified, its polarity is
reversed. By inverting the negative side and adding it 1:1 to an unchanged
positive, a balanced input wastes none of the available signal energy. In doing
so, it also subtracts all the radiation picked up along the line. Random noise
is unaffected, but you'll hear no hum, and much reduced thyristor noise
(from poorly-screened lighting dimmers). Live, you could not run a rig
without balanced mic lines, and although in the studio cable runs are shorter,
the recorded medium's demand on signal to noise is far greater.
When patching a balanced input/output to an unbalanced one, simply short the
-ve and screen together at the unbalanced input or output.
Fig. 12.1: A balanced microphone line
13.

Start-up

13.1 A-channel setting up procedure
13.1.1 Selecting inputs
MICROPHONE:
• MIC/LINE switch (
FLIP switch ( ) UP
S 3
• LINE: MIC/LINE switch DOWN, FLIP switch UP
• TAPE: FLIP switch DOWN
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) UP, PAD switch ( ) UP,
S 1 S 1a
13.1.2 Initializing channel for gain-setting
1) Set GAIN ( ) and all aux sends (
P 2
(fully counterclockwise).
2) EQ switch ( ) UP (off).
S 10
3) LOW CUT switch ( ) ON for microphones, OFF for signals with desired
S 11
low frequency content.
4) CHANNEL MODE set to PFL (
S 95
5) Channel PFL/SOLO ( ) switch UP (
S 26
6) Check that main PFL/SOLO LED (
7) Channel PFL/SOLO switch (
S 26
13.1.3 Auditioning a signal
1) Make a typical noise, or roll the tape. The -20 dB light should flicker,
showing that a signal is present. There should also be some activity at the
MAIN MIX bargraph meters, indicating the SOLOed level.
2) For LINE INPUTS: Adjust GAIN control (
regularly hitting 0 dB.
3) For MIC INPUTS: If your meters are reading 0 dB although the GAIN control is
completely turned counterclockwise, push the PAD switch (
the input signal by 20 dB before you continue the gain adjustment.
4) TAPE inputs do not pass through the GAIN pot (
important to match the operating level of the desk (-10 dBV or +4 dBu) to
that of your machine. If the signal is low (due to incorrect operating level
setting or too low a level having been recorded to tape), try the -10 dBV
setting. If too high, try +4 dBu. If neither gives a good level, try patching the
tape track output into a line input and repeat steps 13.1.1 and 13.1.2.
5) lf EQ is used, repeat steps 13.1.1 & 13.1.2.
6) If an insert is used to patch in a compressor, gate, EQ, etc., use any
outboard processor's BYPASS or EFFECT OFF switch to A/B monitor the effect.
Adjust the processor's output level so that effected and bypassed signals
are level matched.
7) Channel PFL/SOLO switch ( S 26
13.2 Desk/tape setting up procedures
13.2.1 Desk normalization
All board settings should be set to the normal default condition before or after
every session. Usually faders are set to zero (minus infinity), EQs set flat and
switched out, trimpots and channel aux sends turned fully anticlockwise etc.
The natural initial setting for some pots, e.g. master aux sends, is unity gain.
However, some settings, such as selecting PRE or POST for channel aux sends
and whether TAPE or MIC/LINE is flipped onto B-channel etc. will depend
on the operating environment, whether in a MIDI or A/V suite, 24-track
studio or live venue, or even just on the engineer's preferred way of working.
Ultimately, the object of the excercise is:
13.2.2 Multitrack initialization
Set up the multitrack so that any track in "record ready" condition has its input
monitored when the tape is stationary. Place all tracks to be recorded into
"record ready" status (once a recording has been made, these tracks should
automatically switch to tape playback). Check that the input levels to each
TRACK are optimized before recording commences.
, , and ) to OFF
P 12 P 13 P 14 P 15
UP).
off).
L 26
) is not lit.
L 95
) DOWN ( and should light).
L 26 L 95
) until transient peaks are
P 2
) to lower
S 1a
). This is why it is
P 2
) UP. Move onto next channel.