the sound man

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2011

Call Theeditor

Ntege Eric

2/2/2011

The Sound Man



CABLES

Cables carry an audio or video signal from one device to another such as DVD players and TVs,stereo receivers and speakers, and computers and video projectors. Cables don't change the

nature of the audio or video signal they carry. They don't convert or process signals in any way.

That's the job of the devices on either end. A cable in itself is just the messenger. Cables aremade up of three basic parts:

1. CONDUCTOR

The conductor is the wire that actually carries the signal.

2. SHIELDING

One or more layers of shielding prevent the wire from acting as an antenna that picks up

radio frequency interference (RFI) and electromagnetic interference (EMI)

3. CONNECTOR

The connector is the plug at the end of the cable that connects to your device.

Cables are important components of any home stereo or home theater setup. If you don't use the

right cables for the right job then you could end up with a below an average level of sound or picture quality. And if you use cables that are damaged or otherwise junky, you could really end

up with a lousy experience. We can chose to look at the overwhelming amount of cable types

into three categories: audio-only, video-only and audio/video cables that carry both sound and picture.

AUDIO CABLES

1. The most common audio cables are called analog RCA cables. These are the cables with

red and white, or sometimes red and black connectors. RCA cables are widely used toconnect devices like VCRs and DVD players to TV sets or CD players to stereo

receivers. RCA audio cables come in pairs with two connectors on each end, a red one for right stereo and a white (or black) connector for left stereo. They are often bundled with

video cables. Experts recommend gold-plated RCA connectors for extra protection

against corrosion, especially if you live in a humid environment

2. The other most common type of audio cable is speaker wire. Speaker wire runs from astereo receiver to all speakers except the subwoofer (that requires a coaxial cable). Each

speaker needs its own dedicated wire. Speakers not only receive audio signals via speaker wire, but also power. Speaker wire is made from 99 percent oxygen-free copper and



usually comes "unshielded," which means you can see the copper conductor. Speaker wire comes in different thicknesses or gauges rated from 12 to 18 (thickest to thinnest).

As a general rule, the longer your speaker wires, the thicker the gauge you should use.For speaker wire lengths up to 20 feet (6.1 meters) long, 14-gauge is sufficient, but

anything longer than 60 feet (18.3 meters) requires 12-gauge wire.

3. Most audio recordings are digital nowadays, and there are several newer cables thatspecialize in carrying high-bandwidth digital audio signals. O ptical digital cable (alsoknown as fiber-optic and Toslink) transmits audio signals as pulses of light and is

impervious to interference

4 . Another digital audio cable is called digital coaxial . It looks the old coaxial cables that

connect satellite dishes or cable TV signals to televisions, except this is speciallydesigned to carry digital audio. You'll find optical and digital coaxial jacks on newer

DVD players, CD players and stereo receivers.

5. XL R cable originally designed for professional audio use, XLR audio cable is used primarilywith high-performance audio gear. The connector has three pins ² a positive conductor, a

negative conductor, and a ground. The ground wire helps reduce electronic noise throughoutthe cable. A clasp built into the round XLR plug locks it tightly into the socket, ensuring asecure connection. XLR cables are also used with microphones requiring "phantom power."

An electrical charge runs through the ground wire, powering the microphone's internal pre-amps and allowing it to function.

V IDEO CABLES

1. The most common type of video cable is called composite video. A composite video

cable consists of one yellow RCA connector that's usually bundled with red and whiteRCA analog audio cables. It's called composite video because all of the video

information -- color, brightness and sync -- is composited, or squeezed, onto one cable.Composite video cables were designed for older TVs and have a maximum resolution of

330 lines. They're fine for watching VHS tapes on the old TV in the basement, but if you

have a newer television, or an HDTV, composite video cables simply won't cut it.

2. S -video cables are a step up from composite video with a maximum resolution of 400

lines. You will recognize an S-video cable by its circular, nine-pin connector. S-videoseparates color information from picture information, resulting in a crisper image.



Although S-video jacks are found on a lot of TVs, DVD players and home theater receivers, the cable's initial popularity was quickly eclipsed by component video.

3.

Component video cables consist of three RCA connectors colored red, green and blue.With component video, not only is color separated from picture, but the color portion issplit into two separate signals. The result is a super-sharp image with deep color

saturation. Component video cables are ideal for connecting high-definition videocomponents like Blu-ray players and HDTVs. Most home theater receivers come with

several sets of component video jacks.

4 . DVI (digital video interface) cables were designed specifically for use with HDTVs and

other high-definition video components. They have large, 18-pin connectors that look

like computer cables. DVI cables offer the exact same image quality as component videocables, except that DVI comes with a built-in copy protection protocol called HDCP(High-bandwidth Digital Content Protection).

5. VG A ( V ideo G raphics Array) cables while used primarily for computer monitors, VGAcables also connect to LCD flat-panel screens that display images from both traditional

audio/video and computer video sources. These 15-pin connectors carry packets of digitalinformation in a different format than that coming from other sources such as DVD players

or cable boxes.

6. RGB ( D-sub 15-pin) cable Found on some HDTV-ready TVs and HDTV tuner boxes, RGB

connections are used for transferring video signals, including high-definition content. Asimplied by its name, RGB sends the red, green, and blue components of the video signalalong separate paths. Though RGB connections can take a number of forms, one that's increasingly common on

TVs and set-top boxes is the D-sub 15-pin jack . If you own a computer, D-sub 15-pinconnections may look familiar ² they're the same ones found on standard VGA-typecomputer monitors. RGB connections pass video signals in the analog domain.

AUDIO-V IDEO CABLES

1. For years, coaxial video cables were one of the only choices for connecting video

components. Coaxial video cables have that famous one-pin connector, sometimes calleda stinger that can either be pushed or screwed into place. Coaxial video cables are now

mostly confined to outside connections, such as satellite TV or cable TV lines that comethrough the wall. A single coaxial cable carries both video and audio signals.



2. H DMI cables are an updated version of DVI. HDMI cables were also designed for usewith HD components, but their connector is much slimmer, like a large USB cable.

HDMI also includes HDCP copy protection

3. In Europe and the UK, the most popular dual-purpose cable is called S CART ( S yndicat

des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs). SCART cables have fat,21-pin connectors. In Europe, SCART cables do the work of RCA analog audio cables as

well as composite, s-video and component video cables, but they can't carry high- bandwidth digital video or audio signals, such as those necessary for high-definition TVs.

4 . F ireWire , or IEEE 1394, cables are mostly associated with connecting devices tocomputers, but a few high-end home theater receivers and HDTVs now come with

FireWire ports. FireWire is capable of carrying compressed MPEG-2 video and digitalaudio. You might use a FireWire cable to connect a digital video camera directly to your

home theater system to show off some unedited footage.



Analog RCA Cable

Composite video cable

Speaker wire Component video

Coaxial video cable

HDMI Cable



BALANCED AND UNBALANCED LINES (optional to students)

Many people refer to anything with a 3-pin XLR-type connector as a ³balanced´ line but inreality, a lot of equipment has unbalanced inputs and outputs that are carried on XLR connectors.

Lets look at the unbalanced configuration; in many electrical systems, there Is always a need

for a reference point for their voltages generally referred to as the ground along which the ³hot´signal voltage ³swings´ positive (above) and negative (below) while the ground remains with itsreference at ³zero volts´ and in a cable connecting two pieces of equipment, the shield is used as

signal ground. The larger the system and the greater the distances between the source and load,the less effective this unbalanced configuration becomes and may cause a lot of problems.

The voltages of a balanced line are not referenced to the ground or common. Instead, the signal

is carried on a pair of conductors with the signal applied to this pair differentially, their levels arethe same, but their polarities are opposite and they alternate with the frequency of the signal, andgive a total signal level which is the difference between the two individual voltages. The

interference cancels itself and hence a common mode rejection.

Example:

For example, if one conductor is at +5 volts, the other will be at -5 volts, and the signal level will be 10 volts.

Total Signal level = +5 volts minus -5 volts

= +10volts

the sound man

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