Handbook for Sound Engineers

Magnetic Recording and Playback 1041

28.1 Introduction

Many things have changed since the first, second, and
third editions of this book were written. Magnetic
recording is may still be the dominant storage tech-
nology, but its dominance is slipping. The everyday use
of analog reel-to-reel recorders and longitudinal DASH
digital tape recorders is virtually gone as are helical
scan modular digital multitrack recorders. Computer-
based systems storing data on random access hard disk
drives are still popular, but as the price comes down on
memory-based recorders that have no moving parts at
all, these devices will certainly win out in the end.
The driving factor behind this shift is economy in
both the acquisition and operating costs of the newer
formats. The new systems utilize techniques and
components that were developed and are mass produced
for the consumer and computer markets, not just the
very limited professional audio market.
We will first explore the underlying technologies
common to all magnetic recorders, old and new. In spite
of the rapid growth of digital techniques in audio,
analog recording is by no means dead. Many albums are
still recorded and mastered using analog audio
recorders. In addition, the audio (and video) archives of
the second half of the twentieth century are stored in
vaults on millions of reels of analog tape. As a result,
we will need qualified tape recorder operators and
maintenance technicians for many years to come.
Unfortunately, however, much of the knowledge
about analog audio recorders and the mentors who
taught this information are slipping away. This chapter
will provide an overview and in some cases more detail
than the casual reader requires. A full treatment of the
theory and practice of analog recording and specifically
magnetic recording is clearly beyond the scope of this
work. We hope that this will whet the appetite of some
and spur others on to write more comprehensive
treatments.
The roots of the modern-day tape recorder can be
traced to Germany in the mid-1930s. Two German
companies, AEG and IG Faben, worked together to
develop the concept of recording on a coated tape. AEG
built the machine and IG Faben developed the magnetic
particles and manufacturing methods for the tape.
Although few people outside Germany took note, the
German tape recording industry flourished, with 5
million meters of tape being produced in 1939, Fig. 28-1.
The German machines, using a form of plastic tape, were
vastly superior to English recorders using steel tapes and
American recorders using spools of steel wire.

At the end of World War II, the victorious Allies set

aside all of Germany’s patents as a form of reparation

for the war. As a result, the wealth of German tape

recorder technology was quickly and freely exploited in

the United States and many other countries. Within just

a few years tape recording replaced disk cutting as the

primary method of recording information.

Magnetic tape offered several valuable advantages

over phonograph disk recording and even the American

fledgling wire recorders, including improved signal to

noise ratio, lower distortion, and better frequency

response. None of these quality features triggered the

quick adoption of tape recording by the American radio

networks.

The networks needed the ease of use, especially the

ability to create undetectable edits by cutting and

splicing the tape. The recorders also had an important

secondary benefit—the ability to stop and quickly

restart recording. (One does not stop a record cutting

lathe in the middle of a cut!)

Both of these features stem from the nature of the

tape recording. Tape recording is a serial process that

distributes the audio events on a very long piece of tape.

The time of the event is implicitly encoded in the posi-

tion of the event along the tape. The editing scissors and

tape now become a time machine that can alter the

apparent time of an event by relocating the tape

segment of the event to a new position in the reel.

Editing is merely playing tricks with this time machine

to remove or replace events to alter the program.

Ironically, more than 50 years later the pendulum has

swung back, turning the serial nature of tape into a

shortcoming. Most operations in a recording studio

require one or more replays of previously recorded

material. During a mixdown session, for example, the

same song may be replayed 500 times before the final

mix is finished. Each of these replays requires time to

rewind to the head end of the desired selection. A

3-minute tune recorded at 30 in/s occupies 450 ft of

Figure 28-1. German Magnetophon, 1935. This portable

magnetophone weighed over 100 pounds. Courtesy BASF

Corporate Archives.