# WHAT IS IMPEDANCE? Impedance (Z) is the resistance of a circuit to alternating current, such as an audio signal. Technically, impedance is the total opposition.

## Presentation on theme: "WHAT IS IMPEDANCE? Impedance (Z) is the resistance of a circuit to alternating current, such as an audio signal. Technically, impedance is the total opposition."— Presentation transcript:

WHAT IS IMPEDANCE? Impedance (Z) is the resistance of a circuit to alternating current, such as an audio signal. Technically, impedance is the total opposition (including resistance and reactance) that a circuit has to passing alternating current. Impedance (Z) is the resistance of a circuit to alternating current, such as an audio signal. Technically, impedance is the total opposition (including resistance and reactance) that a circuit has to passing alternating current.

Hi z = Line level Hi z = Line level Low z = Mic Level Low z = Mic Level Direct Box changes impedence from line level to 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 high impedance circuit tends to have high voltage and low current A low impedance circuit tends to have relatively low voltage and high current A low impedance circuit tends to have relatively low voltage and high current

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

Connecting Devices When you connect two devices, one is the source and one is the load. 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 source is the device that puts out a signal. The load is the device you are feeding the signal into. 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. The source has a certain output impedance, and the load has a certain input impedance. Its important to match the output impedance of the source to the input impedance of the load Its important to match the output impedance of the source to the input impedance of the load

Matching Impedance If the source impedance equals the load impedance, this is called "matching" impedances. 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. It results in maximum POWER transfer from the source to the load.

low-Z source to a high-Z load Suppose the source is low Z and the load is high Z Suppose the source is low Z and the load is high Z There is no distortion or frequency-response change caused by this connection. 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. 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 If you connect a high-Z source to a low-Z load, you might get distortion or altered response 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. 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 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. 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.

high-Z source to a low-Z load A direct box or impedance-matching adapter does this. A direct box or impedance-matching adapter does this. The adapter is a tube with a phone jack on one end and a male XLR connector on the other. Inside the tube is a transformer. The adapter is a tube with a phone jack on one end and a male XLR connector on the other. Inside the tube is a transformer. Its primary winding is high Z, wired to the phone jack. The transformer's secondary winding is low Z, wired to the XLR Its primary winding is high Z, wired to the phone jack. The transformer's secondary winding is low Z, wired to the XLR

high-Z source to a low-Z load You plug the guitar cord into the phone jack, and plug the XLR into a mic input in a snake or mixer You plug the guitar cord into the phone jack, and plug the XLR into a mic input in a snake or mixer Use it with a bass guitar, electric guitar, or synth. Use it with a bass guitar, electric guitar, or synth. This impedance-matching adapter works, but is not ideal This impedance-matching adapter works, but is not ideal. The load it presents to the bass guitar might be 12 kilohms, which will slighly load down the high-Z guitar pickup, causing thin bass.. The load it presents to the bass guitar might be 12 kilohms, which will slighly load down the high-Z guitar pickup, causing thin bass.

high-Z source to a low-Z load An active direct box solves this problem. In place of a transformer, the active DI usually has an FET (Field Effect Transistor). The FET has a very high input impedance that does not load down the bass guitar. An active direct box solves this problem. In place of a transformer, the active DI usually has an FET (Field Effect Transistor). The FET has a very high input impedance that does not load down the bass guitar.

Active direct box

Low z – High z mics Most mics are low Z, and all mics with XLR (3-pin) connectors are low Z. 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 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 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. If your mixer has XLR inputs, they are low-Z balanced.

Balanced and Unbalanced

Balanced connections A ¼ balanced connection uses three wires A ¼ balanced connection uses three wires Tip Signal + (Positive) Tip Signal + (Positive) Ring Signal - (Negative) Ring Signal - (Negative) Sleeve (Ground ) Sleeve (Ground ) TRS TRS

Balanced connections An XLR balanced connection uses three wires An XLR balanced connection uses three wires Pin 1 (Ground ) Pin 1 (Ground ) Pin 2 + (Positive) Pin 2 + (Positive) Pin 3 - (Negative) Pin 3 - (Negative)

Female Male

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

Balanced connections The audio signal is sent at equal level but opposite polarity on the + and – wires. The – signal gets inverted and adds to the + signal at the receiving end. However, any interference picked up by the cable is injected equally into both the + and – wires and therefore cancels out at the receiving end where the interference on the - wire is inverted. The audio signal is sent at equal level but opposite polarity on the + and – wires. The – signal gets inverted and adds to the + signal at the receiving end. However, any interference picked up by the cable is injected equally into both the + and – wires and therefore cancels out at the receiving end where the interference on the - wire is inverted.

Unbalanced An unbalanced connection uses two cable wires An unbalanced connection uses two cable wires Signal Signal Ground Ground

Types of Cabling ¼ unbalanced line/instrument cabling ¼ unbalanced line/instrument cabling XLR balanced cable used for microphone and line level connections XLR balanced cable used for microphone and line level connections RCA unbalanced line level/ phono connections RCA unbalanced line level/ phono connections Speaker cable, various gauges depending on the application Speaker cable, various gauges depending on the application AC Cabling AC Cabling Patch bays are not common in live sound Patch bays are not common in live sound Mutipins ( Snakes, outboard racks, consoles ) Mutipins ( Snakes, outboard racks, consoles ) Inserts ( Tip, Ring, Sleeve, unbalanced x 2 ) Inserts ( Tip, Ring, Sleeve, unbalanced x 2 )

Insert Cable

Pg. 294 Pg. 294 Gives you an unbalanced input and output from a tip ring sleeve connector on the console Gives you an unbalanced input and output from a tip ring sleeve connector on the console Eqs, Compressors, Gates, Effects for a single channel Eqs, Compressors, Gates, Effects for a single channel English an American consoles may be wired differently English an American consoles may be wired differently If no signal is present flip input and output on the device being inserted If no signal is present flip input and output on the device being inserted

Speaker Cables Can be used with ¼, Banana Plug or Speakon connectors. Can be used with ¼, Banana Plug or Speakon connectors.

¼ Speaker Connector

Tip Positive + Tip Positive + Ring Negative – Ring Negative – Do not use for instruments may cause buzz 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 ) Vice Versa ( Do not use Instrument cables to run speaker, may short amplifier, causing failure or damage )

Banana Plugs 2 conductor connector positive and negative 2 conductor connector positive and negative Fit into binding terminals on amplifiers Fit into binding terminals on amplifiers Tab is usually wired to the negative terminal Tab is usually wired to the negative terminal Can be piggy backed, connected to each other Can be piggy backed, connected to each other Recently outlawed in Europe Recently outlawed in Europe

Binding Posts

Speakon Connectors Three different types Three different types NL2 NL2 NL4 NL4 NL8 NL8

Speakon Connectors Industry Standard Industry Standard NL2 ( Two Pin Connectors ) +1 -1 NL2 ( Two Pin Connectors ) +1 -1 Used for Single Speaker Connections Used for Single Speaker Connections NL4 ( Four Pin Connectors ) +1 -1, +2 -2 NL4 ( Four Pin Connectors ) +1 -1, +2 -2 Used for two Speaker Connections ( Bi- Amp) Used for two Speaker Connections ( Bi- Amp) NL8 ( Eight Pin Connectors ) +1 -1, +2 -2, +3 -3, +4 -4 NL8 ( Eight Pin Connectors ) +1 -1, +2 -2, +3 -3, +4 -4 Used for 3 or 4 way Speaker Connections Used for 3 or 4 way Speaker Connections

Speakon Connectors No universal wiring configuration No universal wiring configuration Check amplifier specifications for pin wiring configuration Check amplifier specifications for pin wiring configuration

NL 4 Speakon Coupler

NL 8 Speakon Coupler

M/XLR to ¼

M/XLR Turnaround

Fem/XLR Turnaround

RCA Adaptors RCA to ¼ RCA to ¼ ¼ to RCA ¼ to RCA Fem RCA to Fem RCA Fem RCA to Fem RCA

XLR Split and Y Cable

AC Alternating current Alternating current Standard circuits are 115 volt 15amp 60Hz Standard circuits are 115 volt 15amp 60Hz 1 amp = approximately 100 watts 1 amp = approximately 100 watts Rule of thumb Maximum amount of power you can draw from one 15 amp circuit is approximately 1500 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 Powered Speakers Powered Speakers Effects outboard equipment Effects outboard equipment Instrument amps Instrument amps Keyboards Keyboards Computers Computers Consoles Consoles International Electrotechnical Commission International Electrotechnical Commission

Cabling Tips Dont buy cheap cable Dont buy cheap cable Keep all cable runs tidy Keep all cable runs tidy Do not run cables through the performance area Do not run cables through the performance area Keep ac cabling and audio lines separate whenever possible to reduce noise 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 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 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 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 Leave speaker cable slack by the speakers not the amps

Cabling Tips Do not share ac power with lighting Do not share ac power with lighting Use the proper length cable for the application whenever possible Use the proper length cable for the application whenever possible Use Sub snakes whenever possible to reduce clutter Use Sub snakes whenever possible to reduce clutter Use strain relief whenever possible Use strain relief whenever possible Dont tug on cables Dont tug on cables Wrap over under Wrap over under Pack up and wrap cabling in the reverse order of running them Pack up and wrap cabling in the reverse order of running them

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