6/30/2009
1
The Machine
Compact Discs
The compact disc has replaced the vinyl record (black label disc) for mist applications in
radio.
The advent of recordable CDs – compact discs can be recorded at the station – offers
exciting possibilities because it allows for storage and quick retrieval of sounds specific to
the station, such as station ID’s or jingles.
Compact Discs
The compact disc in 2 sizes (both less than 5 inches in diameter), the CD resembles a
traditional vinyl disc.
The information on the CD is read by a laser beam contained in a special CD player.
Compact Discs
Unlike a vinyl record, a CD does now have grooves. And because the disc itself is no
touched physically by a stylus. It is less subject to wear than a standard phonograph
record.
Compact Discs
But there is another, more profound difference between the conventional phonograph
record and the CD which is the phonograph record is an analog recording, whereas the CD
is a digital recording.
The word analog means sth that shows a resemblance or similarity to do sth else.
Compact Discs
In the case of analog recording, it means to produce a series of sound waves that closely
resemble the sound waves of the original signal.
We use the term analog recording to refer to any conventional transduction techniques
involving audiotape or vinyl records.
Compact Discs
Digital recoding means using samples of sound to produce a recording that is stored in
computer language – the on and off binary code of digital technology.
The exact method by which sounds are transcuced into digital information is not
particularly relevant to radio work,
Compact Discs
But the following basic points are important.
Digital recordings actually comprise numerically transcribed samples of the original
sounds, so in engineering terms, the digital recording is a collection of samples of sound
and not an analog of sound – hence the difference un a word usage.
Compact Discs
Digital recording produces a cleaner-sounding signal. Very little (if any) extraneous noise
is introduced into the system during digital recording and playback – no tape hiss, no
scratching of a stylus in worn grooves.
The cleaner technology produces a different sound than analog, many listeners
characterize it as ‘cleaner’ and unquestionably noise is reduced.
Compact Discs
However, some listeners claim not to like the digital sound as much as analog. Many
listeners think that it is too harsh, too mechanical or too unnatural.
Compact Discs
The preceding points have contributed to an explosion of compact disc in radio. Even
though the CD is only one link in the audio chain (since the signal still must pass through
many analog devices). Listeners feel that the CD sound I superior and many radio stations
have converted entirely to playing CD.
Compact Discs
Professional-quality compact disc-players can store many disc with virtually instant access to any cut on any disc. This make CDs an excellent choice for automation applications or in
situations where partial automation is used to assist the on air operator.
Compact Discs
Moreover, CDs provide what listeners seems to want in audio quality. Many stations
advertise themselves as being ‘all-CD’, and ratings reflect the all-CD format’s initial success
in the so called fidelity wars.
Compact Discs
Difficulty in handling CDs was once viewed as a drawback to the advancing technology, but
that perception changed as the hardware became more thoroughly established and refined
and as production and air staff become more accustomed to handling the CDs.
Compact Discs
Most experts maintain that the majority of CD ‘crashes’ have been due to poor handling by
production personnel. CDs are no immune to damage; surface scratches can badly impair
playback, and damage to the disc can result in poor audio quality, skipping, or shutdown of
the playback.
Compact Discs
CD playback is generally quite simple. Insert the disc into a mechanized drawer, which
closes automatically and brings the disc into position for playback.
The laser-reader works in reverse of a typical stylus, reading the disc from the inside out
toward the edge.
Compact Discs
CDs have several cuts, and a selector on the machine allows you to pick the cut you want
to play (select track 3, for example).
Unlike standard records, CDs have information only on one side, but that one side can hold
up to an hour of program material.
Compact Discs
When CDs are automated, the cut members are programmed into the computer. Methods
of programming range from a simple computer instruction, to play at random without
repeating any cuts for a certain time, to complete program control cut-by-cut and hour-byhour.
Compact Discs
Recordable CD-Rom, known as CD-R, allows you to ‘burn’ your own recording.
Although the technology is still not universal to radio stations, many produces do want to
‘burn their own’ in order to put frequently used sound elements on a durable and easily
accessible medium.
Compact Discs
The process is fairly complex, requiring not only a burner but also a computer with a
healthy hard drive. For example, atypical burnable CD-Rom holds 74 mins of data – data
that must first be loaded into your computer hard drive. Seventy-four mins of studio will
occupy about 718MB.
Structure of Turntable
A turntable operates in the same way as a record player, except that it is heavier-duty
device and uses a different type of mechanism to turn the record.
The broadcast turntable has several components. Although some minor operational and
cosmetic differences exist among various turntable models, all work in much the same
fashion.
The plate
The disc us plated on the plate; this is the part of the turntable that actually turns around.
The Switch
The switch, also known as start switch, is a smooth action, noiseless switch that turns the
turntable on and off.
It is noiseless because you do not want a click sound while the microphone is turned on.
The Speed Control
The speed control on some turntable resembles the gearshift in a manual-transmission
auto.
The operator can select from among speeds 33 1/1, 45 and 78 rpm (revolutions per
minute) by merely pressing one of the three buttons.
The Speed Control
The 12-inch discs play at 33 1/3 (sometimes shortened to read 33 on turntables settings),
whereas the smaller discs with the large holes play at 45 rpm.
Although 78rpm ate not made anymore; many turntable units retain the option of playing
the speed.
The Speed Control
On some models (particularly older models), there is a neutral position too, which allows
the motor to idle out of gear.
The Drive Mechanism
The gearshift controls a rubber drive wheel, which makes contact with a rim on the inside
of the plate.
Some newer broadcast turntables are known as direct-drive turntables, that is, the motor
drives the plate directly.
With these turntables, there is no neutral position, and speed change is accomplishes
electronically.
The Tone-arm
The tone-arm is the movable device that is put onto the disc.
At the end of the tone-arm are the stylus and cartridge.
The stylus is usually a pointed piece of diamond; some people call it a needle, but it really
is not one.
The Tone-arm
The stylus is attached to a strip metal called cantilever, which in turn is attached to the
cartridge.
The cartridge translates the physical vibration of the stylus into an electrical signal.
The Tone-arm
The process of changing one form of energy into another is called transduction; this is a
very important concept, as similar to the process of a microphone.
The Disc
Where do the vibration picked b the stylus come from? They are impressed into the
grooves on the disc.
The vibrations cut into grooves correspond to variations in the sound that was recorded.
Actually, the vibration patterns are pressed into the grooves of the dics.
The Disc
At the beginning of the manufacturing process, the master disc is cut with a stylus, which is
connected to the output of a tape machine.
When the master disc is cut, an electrical signal is transduced into a physical vibration.
The Disc
There are gaps between the cut (tracks), or individual pieces of music, on the disc; these
separating grooves and the groove at the beginning of the disc) carry no sound. They are
called lead grooves.
The Disc
During the operation of the turntable, you will want to place a disc on the plate, place the
stylus at the beginning of the cut you select, and position the disc so that the beginning of
the music will start immediately, or at least within a second or so or you starting the turntable.
The Disc
Positioning the disc is called cueing.
Handling Disc
Putting your fingers on the grooves of the disc will coat the grooves wear out, or worse,
the stylus may picked up that oil, causing the sound quality of the playback to deteriorate.
Handling Disc
You can avoid this problem by handling the disc shown. To turn the disc over, hold the
edge of the disc with the palms of your hands and flip it.
Handling Disc
These ways of handling discs may seem awkward at first, but with practice, you will find
that they become second nature.
Good handling, with clean, static-free disc will produce much better audio quality.
Cueing a Disc
The first step in cueing the disc is to select the cut you wish to play and place the stylus in
the lead grooves (the gape preceding the cut).
If the cut that you wish to play is the first on the disc, place the stylus at the beginning
groove.
Cueing a Disc
All cueing operations involve a backtracking of the disc. You will spin the record backward
and forward until you have pinpointed the spot where the sound begins.
Cueing a Disc
There are 3 methods of cueing a disc:
Spinning the plate
Spinning the disc
Slip cueing
Spinning the plate
Put the turntable speed control into neutral, as this will enable the heavy metal plate spin
freely.
Start the plate spinning with your hand; you should try to spin it at approximately the same
speed at which it normally spins.
Spinning the plate
The plate is heavy and will keep up to speed for a surprising amount of time.
Drop the stylus in the beginning or separating grooves and let the disc turn until the sound
begins. (Remember to use the sue or audition channel of the console so that the cueing
noises ill not go out over the air.)
Spinning the plate
Then stop the motion of the disc with you hand, and move the plate in the opposition
direction, backtracking the disc.
By rocking the disc clockwise or counterclockwise, you will be able to pinpoint the exact
spot where the sound bagins.
Spinning the Disc
The pieces of hard rubber or (on very old turntable) felt covering the turntable plate
provides just the right amount of friction. This materials holds the disc as the plate spins
but also allows the operator to spin the disc separately from the plate.
Spinning the Disc
To cue up by spinning the disc, leave the speed selector in gear; this way, the plate will not
spin freely.
Drop the stylus into the grooves preceding the cut you want to play.
Then, placing your finger on the label, spin the disc until you hear the first sound.
Spinning the Disc
This method is somewhat difficult to do, and it is not as popular as spinning the plate.
Slip-cueing
To perform slip-cueing, first find the point where the sound begins, either by spinning the
plate or spinning the disc.
With the turntable in gear, and the motor started, hold the disc by the very edge.
The
Slip-cueing
Then, at the instant you want the music to start, release the disc.
With slip-cueing, of course, you do the actual cueing in the cue or audition channel. You
hold up the turntable before releasing the disc.
Tape Recording and Playback Units
Magnetic tape
Workings of the Reel-to-Reel Tape machine
The heads
The tape transport mechanism
Tape machine controls and indicators
Magnetic tape
Audiotape is a strip of material with a thin coating of iron oxide (a fancy name for rust) on
one surface.
The iron oxide particles line up when they are an electromagnetic field and are the
elements that hold the magnetic information.
Magnetic tape
The backing of the tape – the material over which the coating is applied – is made of
acetate or Mylar.
Acetate is similar in composition to Scotch tape. It is somewhat brittle and can be snapped
easily.
Mylar us a resilient, extremely tough substance that will stretch before it breaks.
Magnetic tape
This is not necessarily an advantage because a snapped tape can be repaired, whereas a
stretched tape can’t.
The most commonly used tape in radio is ¼ inch wide although there are different sizes for
specialized applications.
Magnetic tape
The larger reels need special kind of hub arrangement to hold them on the tape machine.
Workings of the Reel-to-Reel Tape machine
The process if magnetic tape recording will happens when a tape passes by an
electromagnet which arranges the pattern in the particles to correspond of that of the
sound message being fed into the decoder.
Workings of the Reel-to-Reel Tape machine
A device called a head is the electromagnet in the tape machine. The head in a typical tape
recorder perform three functions, but before describing them, let’s see where the heads are
and how the tape is brought into contact with them.
Workings of the Reel-to-Reel Tape machine
A reel-to-reel tape machine, regardless of their design differences, operate in pretty much
the same way.
The tape machine draws the tape from the left reel to the right reel. The technical names
of the left and the right components respectively are supply reel and take-up reel.
Workings of the Reel-to-Reel Tape machine
As tape passes from the supply reel to take-up reel, it is drawn across the heads, where a signal is implanted on the tape or played back from the tape.
The Heads
The heads perform 3 distinct function:
Erase
Record
play
The Heads
The erase head produces a magnetic field, called a flux that scrabbles the pattern of the
iron oxide particles and obliterates any information previously stored on them.
The Heads
The record head produces magnetic filed that arranges the iron oxide particles in a
particular order, storing the information on tape.
The Heads
The playback head reads the patterns formed by the arrangement of the iron oxide
particles and produce an electrical signal carrying the sound information on the tape.
The Heads
The head are always arranged this order, from left to right.
Erase, must come first; if the erase head were sound in line, you would erase whatever had
just been recorded on tape.
The Heads
And it makes sense to have the record head in the second position because this allows the
tape to pass over the playback head, which is in the third position.
The Heads
Since the tape passes the record head immediately before the playback head, the operator
of the tape machine can play back what was just recorded to make sure that there is
indeed a recording on the tape.
Remember: Erase, Record and Playback
The Tape Transport Mechanism
Despite the differences among models, the goal of all tape machines is the same; to pass a
tape across the heads at a constant rate of speed.
The Tape Transport Mechanism
The supply reel contains the tape that will be drawn across the heads.
The take-up reel draws the tape up after it passes across the heads.
The tape guides are precision designed to keep the tape exactly in position.
The Tape Transport Mechanism
The capstan is a revolving metal post that determines the speed of the tape’s movement. It
turns the next piece of equipment – the pinch roller.
The Tape Transport Mechanism
The tape passes between the pinch roller, which is made of rubber and the capstan and is
pulled along at the proper speed. The capstan and the punch roller keep the tape moving
at a constant speed; they are connected to the feed and take-up reels through a series of
clucthes.
The Tape Transport Mechanism
The tape idler arm drops down if the tape breaks; when the idler drops, it shut down the
tape machine’s drive mechanism. This prevents tape from spilling out onto the floor if there
is a break, and it shuts down the drive mechanism when the tape runs completely off either
reel.
Tape Machine Controls and Indicators
Play
Record
Volume- Unit Meter
Fast Forward (FF)
Rewind (REW)
Stop
Speed Select
Play
Depressing the play button, will cause the machine to play back the recording on the tape.
The tape moves from the supply reel, across the heads, to the take-up reel.
The erase and record heads do not operate when the machine is in play.
Record
Usually record button is pushed along with the play button.
When recorded is activated, the record head impresses a signal on the iron oxide particles
on the tape; this is the signal that can be read back by the play head.
Record
When the machine is in record mode, the erase head is also activated there would be no
point in recording if the pervious information on the tape were not removed.
Volume-Unit Meter
Like the meter on the console, the tape machine’s VU meter monitors the signal coming
into the tape machine so that proper levels can be maintained when recording.
There are also separate controls on the tape machine to govern the level of the incoming
signal.
Volume-Unit Meter
It is very important to maintain a proper level on this meter.
Fast-Forward (FF)
The FF control moves the tape forward at a high rate of speed.
Cue
The cue control brings the tape into contact with the heads by defeating the tape lifter; it
allows you to cue the tape when it is in Fast-Forward or in Rewind.
Rewind (REW)
Activating the rewind control causes the tape to move backward, that is, from the take-up
reel to the supply reel.
Stop
Pressing stop brings the motion of the reels to a halt.
Speed Select
This control go governs how quickly the tape moves past the heads.
