Live Sound Quiz 2
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What is a block diagram for?
They are for showing signal flow and structure of a device.
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.
How are block diagrams useful?
they help show signal path for changing or customizing signal path
What is "noise"?
Sound you didn't intentionally create, and don't want to hear
What is the difference between pink and white noise?
Pink noise is equal energy per octave; White noise is equal energy per hertz
Why is pink noise used more often than white noise when testing?
Pink noise better represents how we hear
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
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
What is the purpose of audio snakes?
- save time in setup
- neater than a large bundle of cables
What are the 3 types of cables used in an audio system?
power, mic/line, speaker
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)
What is TRS?
balanced phone plug, low impedance (tip for hot, ring for neutral, sleeve for shield)
What is TS?
unbalanced line level phone plug, high impedance (tip for hot, sleeve for shield)
What is RCA?
unbalanced line level, high impedance; usually used in consumer electronics
What are the mass pin speaker connectors?
Neutrik NL-4 and NL-8
How do you wire an XLR to TRS?
- pin 1: sleeve (shield)
- pin 2: tip (hot)
- pin 3: ring (neutral/cold)
What is a DI used for?
it's used to take a high impedance signal and make it low impedance
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
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)
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.
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.
On an electrical outlet, where is the power, neutral, and earth ground?
- Left (bigger blade): neutral
- Right (smaller blade): hot
- Rounded one: earth ground
What is the voltage at an outlet?
Why is disconnecting an earth ground dangerous?
There is nothing protecting you from being electrocuted
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.
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.
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
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
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
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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