Sound Equipment: Part 1
| Site: | QSC |
| Course: | House of Worship Audio Training |
| Book: | Sound Equipment: Part 1 |
| Printed by: | Guest user |
| Date: | Saturday, 23 November 2024, 2:11 AM |
Description
Lesson Description
In this lesson we discuss source equipment and capture tools that one is likely to find on stage, ie. Cables, stage equipment, microphones. We’ll also discuss basic audio terminology.
Video Transcript
00:15
Every specialized field has its own collection of jargon and audio is no exception.
00:21
When you’re working with others in the audio field, it’s super helpful if you’re all speaking the same language.
00:27
Let’s start with common audio cables.
00:30
It’s important to understand the types of signals that different cables carry.
00:35
First of all, an audio cable can either be unbalanced or balanced.
00:40
An audio cable carrying an unbalanced signal uses two wires: a signal and a ground.
00:47
The signal wire, as the name suggests, carries the audio signal to where it needs to go.
00:53
The ground wire acts as a reference point for the signal.
00:57
However, the ground wire itself also acts like an antenna that can pick up unwanted noise along the way.
01:04
Because unbalanced cables can pick up noise as a signal is sent along the cable,
01:09
they’re best used for short distances, like connectinga guitar to a nearby amp.
01:14
Doing so will minimize the risk for unwanted noise.
01:18
Unbalanced cables should be no longer than 25 feet.
01:22
So, where does the noise come from?
01:25
Noise can come from a variety of electrical and radio interferences,
01:29
but it most commonly comes from power cables, which can create a humming sound if they are near cables carrying unbalanced audio.
01:38
Older, non-LED stage lighting for example, spotlights or dimmers can also add signal interference.
01:46
The best technique for reducing noise when using unbalanced cables is to be careful with cable placement.
01:53
A single perpendicular crossing of power & audio cables is much better than a parallel run.
02:00
If parallel cannot be avoided, leave as much space as possible between audio and power cables.
02:06
So let’s look at some unbalanced cables that you’re likely to work with.
02:11
This is a typical “quarter inch”.
02:13
It’s called that because it’s a quarter inch in diameter.
02:18
It can also be called a TS quarter inch; which stands for tip, sleeve,
02:23
because the connector transfers the signal using the tip of the connector, while the sleeve serves as the ground.
02:30
The TS quarter inch cable is also referred to as an instrument cable.
02:36
Instruments such as guitars and keyboards will use this cable.
02:40
This is a mono cable meaning it sends 1 signal down the line
02:44
This is an RCA cable.
02:48
These aren’t quite as common as they used to be.
02:50
But, you can find these connections on CD and DVD players.
02:55
Some DJ gear utilizes RCA connections as well.
02:59
RCA Audio Cables are an unbalanced analog audio connection
03:02
that sends stereo audio over a right channel which has a red housing, and a left channel, which will either have a white or black housing.
03:11
You might even find RCA audio cables bundled with a video component cable, which will have a yellow housing.
03:19
These bundled cables are commonly used with consumer media equipment such as DVD, Blu-ray players,
03:25
gaming consoles and things of that nature.
03:29
Now for balanced audio cables.
03:32
The structure of a balanced audio cable is similar to an unbalanced cable –
03:36
with one addition.
03:38
A balanced audio cable has a ground wire, but it also carries two copies of the same incoming audio signal,
03:46
sometimes referred to as a “hot” or positive and a “cold” or negative signal
03:52
What’s the difference between the hot and cold signal?
03:56
The two signals are reversed in polarity, so as they travel down the cable, they cancel each other out.
04:03
Think of how adding positive and negative numbers of equal value amounts to zero.
04:09
Once the hot and cold signals get to the other end of the cable, however,
04:13
the polarity of the cold signal is flipped, so that both signals are “in phase”, and perfectly in sync.
04:21
Here’s the really cool part: if the cable picks up noise along the way,
04:26
the noise added to both of those cables is not reversed in polarity.
04:31
So when the cold signal flips in polarity upon arriving at the input to match the polarity of the hot signal,
04:39
the noise that was carried along the cold signal cancels out with noise in the hot signal.
04:45
This "canceling out" process is called "common-mode rejection,"
04:49
with the noise being the "common" signal between the two.
04:54
Because balanced signals send two “in-phase” signals, they’re also louder.
04:59
Roughly 6 to 10 dB. than what unbalanced signals can provide.
05:04
So now, let’s look at some balanced cables.
05:08
This is an XLR cable.
05:10
It can also be referred to as a microphone cable.
05:13
XLR It stands for external line return.
05:17
XLR cables can send balanced audio signals up to 200 feet.
05:23
You can recognize an XLR by their three pin male and female connectors.
05:28
The three pins serving as the ground wire, the hot signal with positive polarity,
05:33
and the cold signal with negative polarity.
05:36
This is a quarter-inch TRS cable. TRS stands for Tip, Ring, Sleeve and can be identified by looking at the cable end.
05:46
Here’s the tip, the ring and the sleeve.
05:51
It can be used to send either mono (balanced) or stereo (unbalanced) signals.
05:56
The cable on your professional audio headphones has a TRS quarter connector.
06:02
This is a stereo 1/8 inch.
06:04
It could be referred to as a TRS 1/8 inch, 3.5mm or a stereo mini plug.
06:11
The structure is the same as the TRS quarter inch but this is smaller in diameter.
06:17
This connector is often used for music or content coming out of a smart device or a computer.
06:23
So, really quickly, I just wanted to clear up a common misconception.
06:27
While it is less common, XLR and TRS cables are also capable of carrying unbalanced, stereo audio.
06:36
Both left and right chann els on one cable to a destination.
06:40
They are however, still susceptible to the noise that unbalanced signals are prone to in these scenarios.
06:47
Ok, Let’s talk about a few other cable types you’re likely to work with.
06:51
This is an NL-4 connector, also commonly referred to as a speakON™ connector.
06:57
This type of connection is the industry standard for amplifier and passive loudspeaker connections.
07:04
They come in a few different varieties relating to the number of connection pins they have.
07:10
You will have NL-2, NL-4 and NL-8 connection types. The common one being the NL-4.
07:18
This is a Euroblock connector.
07:20
Euroblock is short for “European-style Terminal Block.”
07:25
This allows a large number of connectors to be placed on an equipment chassis, for example, amplifiers and digital signal processing units like Q-SYS.
07:35
They are also known as “Phoenix” connectors since a dominant manufacturer is Phoenix Contact.
07:42
They are also sometimes referred to as Combicon connectors.
07:47
The type of cable required, will be dictated by the connection type on any particular device that a connection is being made to.
07:54
So, if a device has a ¼ connection for example, you wouldn’t use an XLR or RCA cable to make that connection.
08:02
On the other hand, some devices might have multiple connection types. In this case, you have a little more flexibility on what cable you use.