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What is a block diagram for?
They are for showing signal flow and structure of a device.
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What is the difference between a block diagram and a schematic?
A schematic has the components and values labeled where a block diagram doesn't.
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How are block diagrams useful?
they help show signal path for changing or customizing signal path
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What is "noise"?
Sound you didn't intentionally create, and don't want to hear
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What is the difference between pink and white noise?
Pink noise is equal energy per octave; White noise is equal energy per hertz
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Why is pink noise used more often than white noise when testing?
Pink noise better represents how we hear
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Why is it important to have good cables?
Good cables make sure to carry a good signal from your other high-end gear; you don't want your quality gear to sound crappy because of cheap cables
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What is the four conductor cable called?
Star Quad or Quad; have a shield and four conductors (2 pairs) that are twisted around each other for extra conductivity
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What is the purpose of audio snakes?
- save time in setup
- neater than a large bundle of cables
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What are the 3 types of cables used in an audio system?
power, mic/line, speaker
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What is an XLR?
balanced mic level, low impedance; 3 pin connector with one shield and a twisted pair of conductors that carry the signal (one out of phase with the other to cancel out interference)
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What is TRS?
balanced phone plug, low impedance (tip for hot, ring for neutral, sleeve for shield)
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What is TS?
unbalanced line level phone plug, high impedance (tip for hot, sleeve for shield)
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What is RCA?
unbalanced line level, high impedance; usually used in consumer electronics
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What are the mass pin speaker connectors?
Neutrik NL-4 and NL-8
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How do you wire an XLR to TRS?
- pin 1: sleeve (shield)
- pin 2: tip (hot)
- pin 3: ring (neutral/cold)
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What is a DI used for?
it's used to take a high impedance signal and make it low impedance
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On a DI box, what does the "ground" switch do?
it lifts the ground if your amp is already grounded so you don't get a ground loop
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What is an insert cable used for? How is it made and wired?
- An insert cable is used for connecting dynamics signal processing to a mixer using a Y-split.
- It's made by wiring two TS plugs to one TRS (both TS have sleeve wired together; one TS has tip to tip, other TS has tip to ring)
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What is the basic principle of balanced audio circuits?
A balanced circuit outputs a low impedance signal via three conductors, a hot, a cold (hot polarity reversed), and a ground.
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How do balanced circuits differ from unbalanced circuits?
- Balanced circuits have two conductors (one is flipped phase) and sometimes a third that is referred to ground. They are less susceptible to pick up interference.
- Unbalanced circuits have two conductors, one for signal and one for ground. They are more susceptible to interference than balanced lines.
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On an electrical outlet, where is the power, neutral, and earth ground?
- Left (bigger blade): neutral
- Right (smaller blade): hot
- Rounded one: earth ground
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What is the voltage at an outlet?
120V AC
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Why is disconnecting an earth ground dangerous?
There is nothing protecting you from being electrocuted
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What are the 3 types of grounds?
- -Earth Ground: literally the electrical
- potential of the earth, which is the round prong on a US standard 120
- volt outlet.
- -Chassis Ground: the connection point
- of a component on the chassis; this is usually connected to the earth
- ground if a 3-prong plug is being used on the equipment.
- -Signal Ground: the reference point for
- expressing signal potentials against.
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Why is grounding important?
- Grounding is how a signal conductor is
- protected against unwanted induced currents (radio frequencies, AC
- power lines, motors, etc.). It also protects against electrocution
- in case there is a faulty wiring or maybe a short.
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How do the 3 grounds interconnect with each other?
Shield (signal ground) gets connected to the chassis ground, which is connected to the third prong on a power cable for the earth ground
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What is a ground loop?
two pieces of equipment share a common earth ground and create a 60Hz hum; only made by things that need to be plugged into an outlet
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How do you prevent ground loops?
- make sure everything is plugged into same earth ground
- use DI box to lift ground in problematic circuit
- use SHUNT adapter to lift ground in cable
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How do you remove a ground loop from a system during setup?
- First locate the source by muting or unplugging different electrically connected components
- once found, plug it into something with a common earth ground
- you can use a DI box or Shunt adapter to lift ground
- if all else fails, use a noise gate
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