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WHAT IS IMPEDANCE - PowerPoint PPT Presentation


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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. A 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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Presentation Transcript
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  • Hi z = Line level

  • Low z = Mic Level

  • Direct Box changes impedence from line level to mic level


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High / Low Impedance

  • A high impedance circuit tends to have high voltage and low current

  • A low impedance circuit tends to have relatively low voltage and high current


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Connecting Devices

  • I'M CONNECTING TWO AUDIO DEVICES. IS IT IMPORTANT TO MATCH THEIR IMPEDANCES? WHAT HAPPENS IF I DON'T?


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Connecting Devices

  • 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


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Matching Impedance

  • 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.


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low-Z source to a high-Z load

  • 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.


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high-Z source to a low-Z load

  • 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.


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high-Z source to a low-Z load

  • 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.




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Low z – High z mics

  • 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.



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Balanced connections

  • A ¼” balanced connection uses three wires

  • Tip Signal + (Positive)

  • Ring Signal - (Negative)

  • Sleeve (Ground )

  • TRS


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Balanced connections

  • An XLR balanced connection uses three wires

  • Pin 1 (Ground )

  • Pin 2 + (Positive)

  • Pin 3 - (Negative)



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Balanced connections

  • The balanced connection has the advantage that it rejects noise and interference that may be picked up on long cable runs


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Unbalanced

  • An unbalanced connection uses two cable wires

  • Signal

  • Ground


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Types of Cabling

  • 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 )



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Insert Cable

  • 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


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Speaker Cables

  • Can be used with ¼” , Banana Plug or Speakon connectors.



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¼” Speaker Connector

  • 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 )


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Banana Plugs

  • 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



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Speakon Connectors

  • Three different types

  • NL2

  • NL4

  • NL8


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Speakon Connectors

  • 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 ( Bi-Amp)

  • NL8 ( Eight Pin Connectors ) +1 -1, +2 -2, +3 -3, +4 -4

  • Used for 3 or 4 way Speaker Connections


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Speakon Connectors

  • No universal wiring configuration

  • Check amplifier specifications for pin wiring configuration




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Adaptors

  • Adaptors are available for every possible application






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RCA Adaptors

  • RCA to ¼”

  • ¼” to RCA

  • Fem RCA to Fem RCA



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AC

  • 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






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IEC

  • Powered Speakers

  • Effects outboard equipment

  • Instrument amps

  • Keyboards

  • Computers

  • Consoles

  • International Electrotechnical Commission


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Cabling Tips

  • 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


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Cabling Tips

  • 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


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