Transcript Electricity and Sound

Connectors and
Cables
Types of connectors and cables
Wiring standards
Soldering principles
Cable testing
Connectors
Microphones
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Professional quality will
always use either XLR
or RTS
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XLR is the most common
 Locking connector for
greater reliability
3 pin XLR
Connectors
Microphones
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Pin out
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Term which defines
which conductors land on
which pins
There are standards for
different devices
The standards change in
different parts of the
world
Pin 1 – Ground
Pin 2 – Signal Hot
Pin 3 – Signal Return
Connectors
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Tip – Ring – Sleeve
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Used for balanced mic
signals
More often used
unbalanced for multiple
channel connections
Balanced
Unbalanced
Pin 1 – Shield
Pin 1 – Signal Return (-)
Pin 2 – Signal Hot (+)
Pin 2 – Signal 1 Hot (+)
Pin 3 – Signal Return (-)
Pin 3 – Signal 2 Hot (+)
Connectors
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RCA plugs
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Sometimes called phono
plug
 Not to be confused with
¼” phone plugs
Always unbalanced
Pin 1 – Signal Hot (+)
Pin 2 – Signal Return (-)
Cables
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Wire
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One individual conductor
Cable
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Two or more conductors combined together in a
flexible jacket
Cables
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Cables in theatrical applications receive very rough
treatment
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Stepped on, genie lifts and forklifts roll over, twisting and
pulling…
Even the best audio equipment in the world will not
work with damaged cables!
Coiling
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The over the forearm method is about the worst thing you
can do to any cable
The wires inside the cable have a natural “lay”.
 They will coil nicely if they are allowed to
Forcing the wires to bend will weaken and eventually break
the wire causing shorts or intermittent connections.
Coiling a cable video
Cables
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Cables should always be run “cleanly”
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Use the shortest lengths you can.
Avoid large coils when possible
 This allows for an easy concentration of induced noise
Never bend cables over sharp edges or right angles
 Dropping a cable over and I-beam for example
Always tie up or tape down under carpets or mats or use
industrial cable covers.
 Avoid using “gaff tape” directly on cable jackets.
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Tape will often leave behind a residue of stickiness
If two adhesive sides come together it is very difficult to remove.
Cables
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Snakes
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A cable with multiple
pairs of conductors, each
with it’s own screen
protected by an overall
insulating jacket
“Tails”
“Break out”
box
Cables
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Loudspeaker cable
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Carries much higher electrical power than mic or line level
cables
Need to be much larger gauge with heavy duty
connectors on each end or bare wires
Wire has it’s own internal resistance which will degrade
the signal before it reaches the speaker
 12 gauge
0.159 Ω / 100 feet
 16 gauge
0.402 Ω / 100 feet
 24 gauge
2.567 Ω / 100 feet
Cable Testing
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Tools of the trade
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Multi-meter
 Device which can measure
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AC & DC voltage
 Remember AC voltage changes with time
 Most meters take and average, NOT RMS value
 RMS = root-mean-square, which is a more accurate means of
measuring voltage
AC & DC current
Resistance
 Continuity
Some meters will measure other things as well
 Battery checker
 Diode checker
Cable Testing
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Oscilloscope
 A device which draws a graph of a changing electrical
signal in real-time
 Allows you to view exactly what the sine wave looks like
 Usually a large bench test piece of equipment not usually
used in simple sound equipment testing
Line tracer
 “Fox and Hound”
 The “fox” puts an AC signal on a wire and the “hound” picks
it up at the other end
 The “hound” looks for the changing magnetic field that the
“fox” produces
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Can be measured through insulation
Soldering
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Here's a summary of how to make the perfect solder joint.
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All parts must be clean and free from dirt and grease.
Try to secure the work firmly.
"Tin" the iron tip with a small amount of solder. Do this immediately, with new tips
being used for the first time.
Clean the tip of the hot soldering iron on a damp sponge.
Many people then add a tiny amount of fresh solder to the cleansed tip.
Heat all parts of the joint with the iron for under a second or so.
Continue heating, then apply sufficient solder only, to form an adequate joint.
Remove and return the iron safely to its stand.
It only takes two or three seconds at most, to solder the average joint.
Do not move parts until the solder has cooled.
Troubleshooting Guide
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Solder won't "take" - grease or dirt present – de-solder and clean up the parts.
Joint is crystalline or grainy-looking - has been moved before being allowed to cool, or
joint was not heated adequately - too small an iron/ too large a joint.
Solder joint forms a "spike" - probably overheated, burning away the flux.
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