Cabling - Pacific Audio Visual Institute

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Transcript Cabling - Pacific Audio Visual Institute

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Hi z = Line level
Low z = Mic Level
Direct Box changes impedence from line
level to mic level
High / Low Impedance
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high impedance circuit tends
to have high voltage and low
current
 A low impedance circuit tends
to have relatively low voltage
and high current
Connecting Devices
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I'M CONNECTING TWO AUDIO
DEVICES. IS IT IMPORTANT TO
MATCH THEIR IMPEDANCES? WHAT
HAPPENS IF I DON'T?
Connecting Devices
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When you connect two devices, one is the source
and one is the load.
The source is the device that puts out a signal.
The load is the device you are feeding the signal
into.
The source has a certain output impedance, and
the load has a certain input impedance.
It’s important to match the output impedance of
the source to the input impedance of the load
Matching Impedance
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If the source impedance equals the load
impedance, this is called "matching"
impedances.
It results in maximum POWER transfer
from the source to the load.
low-Z source to a high-Z load
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Suppose the source is low Z and the load is high Z
There is no distortion or frequency-response
change caused by this connection.
When you plug a low-Z source (microphone) into a
high-Z input you get a weak signal. That's because
a high-Z input is designed to receive a relatively
high voltage from a high-Z mic or instrument, and
so the input is designed to have low gain. So you
don't get much signal amplification.
high-Z source to a low-Z load
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If you connect a high-Z source to a low-Z
load, you might get distortion or altered
response
For example, suppose you connect an
electric bass guitar (a high-Z device) into an
XLR-type mic input (a low-Z load). The low
frequencies in the signal will roll off, so the
bass will sound thin.
high-Z source to a low-Z load
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We want the bass guitar to be loaded by a
high impedance, and we want the mic input
to be fed by a low-impedance signal.
Impedance-matching adapter
Active direct box
Low z – High z mics
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Most mics are low Z, and all mics with XLR
(3-pin) connectors are low Z.
A low-Z mic can be used with hundreds of
feet of cable without picking up hum or
losing high frequencies.
A high-Z mic will lose highs and pick up hum
if the cable exceeds about 10 feet
If your mixer has XLR inputs, they are low-Z
balanced.
Balanced and
Unbalanced
Balanced connections
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A ¼” balanced connection uses three wires
Tip Signal + (Positive)
Ring Signal - (Negative)
Sleeve (Ground )
TRS
Balanced connections
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An XLR balanced connection uses three
wires
Pin 1 (Ground )
Pin 2 + (Positive)
Pin 3 - (Negative)
Female
Male
Balanced connections
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The balanced connection has the advantage
that it rejects noise and interference that
may be picked up on long cable runs
Unbalanced
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An unbalanced connection uses two cable
wires
Signal
Ground
Types of Cabling
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¼ unbalanced line/instrument cabling
XLR balanced cable used for microphone and
line level connections
RCA unbalanced line level/ phono connections
Speaker cable, various gauges depending on the
application
AC Cabling
Patch bays are not common in live sound
Mutipins ( Snakes, outboard racks, consoles )
Inserts ( Tip, Ring, Sleeve, unbalanced x 2 )
Insert Cable
Insert Cable
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Pg. 294
Gives you an unbalanced input and output
from a tip ring sleeve connector on the
console
Eq’s, Compressors, Gates, Effects for a
single channel
English an American consoles may be wired
differently
If no signal is present flip input and output
on the device being inserted
Speaker Cables
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Can be used with ¼” , Banana Plug or
Speakon connectors.
¼” Speaker Connector
¼” Speaker Connector
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Tip Positive +
Ring Negative –
Do not use for instruments may cause buzz
Vice Versa ( Do not use Instrument cables to
run speaker, may short amplifier, causing
failure or damage )
Banana Plugs
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2 conductor connector positive and negative
Fit into binding terminals on amplifiers
Tab is usually wired to the negative terminal
Can be piggy backed, connected to each other
Recently outlawed in Europe
Binding Posts
Speakon Connectors
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Three different types
NL2
NL4
NL8
Speakon Connectors
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Industry Standard
NL2 ( Two Pin Connectors ) +1 -1
Used for Single Speaker Connections
NL4 ( Four Pin Connectors ) +1 -1, +2 -2
Used for two Speaker Connections ( BiAmp)
NL8 ( Eight Pin Connectors ) +1 -1, +2 -2,
+3 -3, +4 -4
Used for 3 or 4 way Speaker Connections
Speakon Connectors
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No universal wiring configuration
Check amplifier specifications for pin wiring
configuration
NL 4 Speakon Coupler
NL 8 Speakon Coupler
Adaptors
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Adaptors are available for every possible
application
M/XLR to ¼”
M/XLR to ¼”
M/XLR Turnaround
Fem/XLR Turnaround
RCA Adaptors
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RCA to ¼”
¼” to RCA
Fem RCA to Fem RCA
XLR Split and Y Cable
AC
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Alternating current
Standard circuits are 115 volt 15amp 60Hz
1 amp = approximately 100 watts
Rule of thumb Maximum amount of power you
can draw from one 15 amp circuit is
approximately 1500 watts
Hubble to Camlock
Camlock, Twist Lock, U-Ground
30 amp Break out
Stove Plug 40 amps
IEC
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Powered Speakers
Effects outboard equipment
Instrument amps
Keyboards
Computers
Consoles
International Electrotechnical Commission
Cabling Tips
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Don’t buy cheap cable
Keep all cable runs tidy
Do not run cables through the performance area
Keep ac cabling and audio lines separate whenever
possible to reduce noise
Try not to run ac lines and audio lines parallel to
each other to reduce noise
Leave mic cable slack by the stand or instrument
Do not leave mic cabling slack at the snake head or
piled up on top of each other
Leave speaker cable slack by the speakers not the
amps
Cabling Tips
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Do not share ac power with lighting
Use the proper length cable for the application
whenever possible
Use Sub snakes whenever possible to reduce
clutter
Use strain relief whenever possible
Don’t tug on cables
Wrap over under
Pack up and wrap cabling in the reverse order of
running them