Capturing the aural moment, while leaving the past behind, couldn't
If you have a storage room full of old cart machines, portable
cassette decks for news, and reel-to-reel machines collecting dust, you
are not alone. Seasoned broadcasters may find it difficult to let go of
the past, but welcome the new choices of the digital recording machines
on the market today, which have replaced their old analog counterparts.
Digital technology is changing on a daily basis, bringing out new ways
to record audio using better and smaller devices. Unfortunately, new
recorders mean new formats and new storage media. Standardization
across the business is fading. Each recording house, voice talent, home
studio, and advertising agency has a favorite format to record in and
assumes that the broadcaster will have a compatible machine to play it
on. Production directors can find themselves scrambling for a way to
play back a spot mailed to them.
When outfitting a production room, it's important to have all of the
major types of audio recorders and players. Yes, you should still have
an open reel machine somewhere in the facility just in case an agency
sends out a spot on tape, and to play those stacks of old tapes on the
shelves. You should also keep a cassette deck in the studio as well.
Many times a client will still ask for a dub of their spot on cassette
to review and keep. Prospective announcers may also send their air
check tapes on cassette still.
Understanding digital recorders
When looking at digital recorders, there are a few key terms with
which you should be familiar: sample rate, bit rate, and data
compression. Basically, a digital recorder is taking repeated
pictures or snapshots of what the audio looks like. Like a movie, if
you have a large number of pictures taken in a short period of time,
and then flip through them, you will see the picture move. Similarly,
if you take multiple snapshots of the audio waveforms and play them
back rapidly, you will be able to recreate the audio. The sample rate
refers to the number of these snapshots taken of the audio every
second. CDs, for example, sample at 44.1kHz, or take 44,100 pictures
per second. Like a movie, the more pictures you take (the higher the
sample rate), the better the quality will be.
Figure 1. The blue line represents the original waveform, the Xs
represent the sample points, and the green line represents the
reproduction of the digitally sampled waveform. This example shows a
32-bit resolution and a sample rate of 20 samples per second. (Click
image for larger view.)
What the recorder is measuring at each sample point is the voltage
or amplitude of the audio waveform. The resolution and sample rate
refer to how accurately that measurement is taken. Just like with
digital cameras, the higher the resolution or sample rate, the better
the quality. Figure 1 shows an audio sample with a 32-bit resolution
and a sample rate of 20 samples per second. CDs are recorded with 16
bits, which translates to a resolution of 65,536. A 24-bit rate audio
expands that resolution to 16,777,216.
The third important term to understand is data compression.
Digital recorders have a limited amount of storage space. It's the same
as the hard drive on your computer. The more data you put on the drive,
the faster you will fill it up. Digital audio in its pure or linear
form will require about 10MB of storage space for one minute of stereo
CD quality audio. This adds up quickly as you continue to record.
Complex algorithms were developed to analyze the audio and find pieces
that can be eliminated without being noticed by the human ear. As you
reduce the data more and more (increase the compression ratio), you
will begin to hear some of the side effects. The trade-off is higher
recording time capacity but at a lower audio quality. When the proper
compromise is found, you can achieve a dramatic increase in recording
time, with virtually no audible quality loss.
With so many legacy systems to choose
from, it may be wise to maintain at least one playback machine per
Digital recorders are no longer just on a wish list, they have
become a necessity to keep up. In today's studios, the new recorders
are now becoming the new “old standards”. Introduced in
1987, Digital Audio Tape (DAT) was the first type of digital recorder
to become widely used by radio stations. Mechanically, a DAT machine is
like a miniature VCR, using a small cassette tape, which is pulled out
of the cartridge by the machine and wrapped around a high-speed
rotating head. One tape will hold up to two hours of audio. As long as
the machine is kept in good operating condition, the DAT will produce
excellent quality recordings. The audio is kept in its purest form by
recording in a linear format, rather than using data compression with
bit rates as high as 24. Typically, the user can select sample rates of
either 44.1 or 48kHz for better than CD quality recordings. Most
machines can automatically step down to a lower 32kHz rate when
necessary to be compatible with some other digital formats. The down
side of the DAT is that it is still basically a tape format with a lot
of moving parts. The tape transports are mechanically complicated.
Heads will still wear in time, and if they are out of alignment, tapes
recorded on one machine might not play back in another. The old
complaint of a machine eating a tape is still common with DAT. I
suggest that you always rewind the tape before trying to eject. While
the use of the DAT format is fading, it's still advisable to have the
ability to play these tapes in the studio.
The next type of digital recorder replaces the tape with a disk.
Some of the early replacement cart machines were called digital carts.
Attempts to use standard floppy disks were close, but didn't quite make
it due to the limited record time per disk. Even at a lower 32kHz
sample rate, these recorders could only muster about 50 seconds of
record time. To overcome this, manufacturers moved to the higher
capacity magneto-optical (MO) disks. While the blanks are more
expensive, they can record several hours of stereo high quality audio
on each disk. Some machines will also record on Zip disks, which will
provide more than 30 minutes of record time.
Figure 2. A comparison of various formats, their media type, and key
operational parameters. (Click image for larger view.)
Another more commonly used disk recorder on the market is the
mini-disk. Through the use of the data compression algorithm called
ATRAC, a small disk can hold up to 74 minutes of audio. With a sample
rate of 44.1kHz and bit rate of 16, it's difficult to tell the
difference between a mini-disk and a CD. Mini-disks are also readily
available in portable models and are great for field recording and news
gathering. Small consumer recorders and blank disks can be purchased at
local electronic stores for less than $200. These inexpensive recorders
even have some basic editing functions on them, allowing a reporter to
record, edit, and send an actuality on the fly. Keep an eye on the
machine, however, as they are getting so small that it's easy to set
one down and lose it.
Since the mini-disk is a popular format, it's a good idea to have
them available in your studio. There's a wide range of choices with
rack mount models starting at just under $600, and costing as much as
$4,000. You should chose a model based on your demand and needs. For
the occasional use, the lower end model is all you need. For a station
with high demand use in production and on-air studios, you should
consider the professional high-end models. These recorders offer more
features, such as the ability to remote start from a console, balanced
analog and AES digital inputs and outputs, more precise cueing, more
robust mechanics, hot key instant starts, and more. Just keep in mind
that even the less expensive models will still give you excellent audio
Removeable media recorders, such as these
from Sony, Marantz and Denon, look and feel like conventional cassette
Most people compare the quality of a digital recording to the
quality of a CD. Since CD quality is highly desired, and because CDs
are used everywhere, from homes to cars to offices to the control room,
easy to use recorders have been desired for some time. The biggest
problem has been the “write once” limitation of the CD. A
small mistake while recording meant starting over with a new blank
disc. This added to the popularity of the mini-disc with its record and
erase capability. With CD recorders becoming almost standard in today's
PC's though, the format is now starting to take off in studios and at
home. You can load your music onto the hard drive of your computer,
then correct any mistakes before dubbing the final copy to the CD.
Blank discs have also come down in price to under a dollar each, and
with their 80-minute audio capacity, they have become one of the most
economical ways to archive old spots and files. While great for studio
use, the CD is still not practical for field recording.
Field recording has always been a challenge. Portable DAT and
mini-disk machines have given us excellent quality far exceeding the
older cassette machines, but both still have complex mechanical
transports, which can wear out and break down from being tossed around
in cars and briefcases. Nothing is more frustrating than stumbling onto
the perfect interview then having the recorder not work properly.
Handheld recorders rely on solid-state
media, shich is sometimes removeable.
The latest wave of portable digital recorders is now available.
These recorders have no moving parts to wear out or break, no tapes to
eat, no disks, no heads to be jarred out of alignment, and no motors.
They use the new plug-in memory cards. These are the same cards used in
digital cameras and portable MP3 players. There are several different
types of memory cards available, such as Flash Cards and Memory Sticks,
and they are available in standard values of 64MB and 128MB, with some
available up to 1.2GB on a single card.
These professional recorders typically offer both linear and some
form of data compression to give extended record time. An example is a
model that uses the MP2 data compression method and allows various
quality selections. Again, the trade-off for quality is an increased
record time. On an off-the-shelf 128MB flash card, you can expect get
about 1.5 hours of CD quality audio, or as much as 6 hours of record
time if you reduce the quality to the “FM radio” mode.
Perhaps the best feature of these recorders takes place when you get
back to the studio. You can eject the memory card out of the recorder,
and plug it into a USB adapter connected to your computer. Files can
then be instantly transferred to your hard drive, where they can be
edited with a software package. With a CD-R drive in your computer, the
final edited copy of your interview, as well as the original raw
unedited audio can be burned and archived to a compact disc. If you
take a laptop computer with you, your car or station van can become a
complete field production facility. The only down side to these
recorders is the cost, although prices are already starting to drop. If
budget is a factor, the portable mini-disk recorder may be your best
option for now.
These are the main types of recorders used today, although there are
still others in use both in the studio and the field. Recorders, which
use internal hard drives, are typically associated with digital editors
and workstations. There are some portable recorders on the market that
use a removable SCSII drive. This allows the reporter to record audio
directly onto a drive, which can then be inserted into a studio
computer for editing. Even DVD recorders are starting to appear on the
scene. These are similar to CDs, but expand the recording time of the
audio from 80 minutes, to about 8 hours of CD quality audio. These will
undoubtedly become a popular method for backing up and archiving
production work in the future.
As technology advances, it's safe to say that we will see new and
better ways to record and store our audio. Data compression schemes are
also improving rapidly, allowing us to store more and more audio on one
disk or flash card. The improvements are exciting, but you must be
prepared to stay up-to-date, and be prepared to train your staff on
operating these newer machines.
Steve Fluker is the director of engineering of Cox Radio,