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Audio Sources
All of our programming at 94X
originates as a CD, a computer file, or a cart. In this section,
we will show you a little of how all these come together to become a
radio program.
The CD's
As we mentioned above, some of our programming, in fact most of it
originates on the CD audio format. In our studio, we have the
capability of playing the CD's directly to the air, or ripping them
into the computer system to be used with psuedo-automation. We
use a dual deck CD player to get the CD's on the air, and one of our
production computers to rip music and ads.
Computer Files
Files that you hear on 94X are often stored in the MP3 format (MPEG I
Layer III) usually sampled at 320 Kbps. As is the case with most
internet programming content, a lot of the files we get from the net to
play requests are of comparatively low quality, around 128 Kbps.
Since we feel quality is more important than storage space, we try and
rip files directly to the PCM or WAV format from the CD, which yields
superior quality to the MPEG formats. We have two computers that are
capable of playing audio over the air. Our air server, and
production computer/phone editor handle this task nicely.
The Carts
Perhapt the oldest of our playback methods are the cart machines. This
technology is similar to 8-tracks except only two tracks of audio are
stored on the tape, traveling at higher speed, yielding much better
fidelity and frequency response stability. Here is what a cart
looks like.
As you can see, the start of the tape is pulled out from the center of
the spool, passed by the heads in the player, pulled by the capstan,
then wrapped around the outside of the spool. The max a cart of
this style can hold is roughly 12 minutes, although this is pushing the
mechanical limits of the tape. Because the tape must be able to
slip in an endless loop, a graphite lubricant is applied to the back of
the tape to prevent sluggish playback and "pullout". This type of
system is also very subjective to wear and tear, as anyone who lived in
the 8-track era can atest to. These machines are maintainance
intensive and are used by only a handful of stations today. They
are however a great way of ensuring engineering job security;)
Microphones
Mics are
also needed to get human audio sources on the air. There really
isnt a whole lot to say about the microphones, as one is fairly similar
to another in how it works. After the mic, we use mic processors
to beef up the on air sound, and reduce studio noise heard over the
air. Part of this signal is also used to feed our phone system.
The Mixing Console
So, we have all this lovely audio
material to work with, now what? The last stop the audio makes in
the studio is the mixing console. Here, all our audio sources are
mixed down into a stereo mix we can broadcast. Our console dates
back to the late 70's but its purpose and function are the same as
those made today, plus the price was right.
The Console has two stereo
outputs, audition, and program. The program bus is the mix which
is heard over the air. The audition bus is used for recording
sources, sending audio down the phone lines, and other internal studio
uses. The cue bus is also included. The cue bus is a
monaural channel that terminates with a small speaker. This alows
the DJ to sync up songs, cue up records, tapes, and CD's before they
are broadcast. It is also used to listen to a caller in a
mix-minus situation.
Our console also has two 8 watt amplifiers built in
for listening to either the program going to the transmitter, or the
off-air monitor.
Now
that our audio is mixed, its off to the processing stage of the
broadcast airchain, but first lets have a look at the telephone
subsystem.....
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