Recording Handbook - Hol.gr

2.Getting Your Sound On Tape
Until recently, "Analog" was the only kind of recording available to most musicians. The wide availability
of DAT recorders, Alesis ADAT 8-tracks, Tascam DA-88 8-tracks and hard disc recorders like the Emu
Darwin, Akai and Vestax machines have forever changed that situation. Still, the process is the same even
though there are different technical considerations and format specific issues to address.
a. The Analog Recording Process
Analog recording devices use a plastic tape coated with magnetic particles moving across a magnetic
recording head at a constant speed to record and playback. There is always an "erase head", first in the
tape path, to erase and re-align the tape particles before they hit the "record head". In the "two-head"
machine there is one head for both recording and playback. The "three-head" design features one head
dedicated to recording, the "sync head", and another for playback, "the repro head". Professional machines
have three heads.
There is a limit to the intensity of the signal that the tape particles can actually absorb and reproduce. The
two parameters that interact to maximize the tape's ability to correctly record and playback are "tape
speed" and "bias". At a faster speed, there is more tape area for a given signal, i.e. more tape particles to
record. Most professional analog multitrack recorders run at 30 ips (inches per second). "Bias" is a process
that was discovered by accident. It was found that when a high frequency signal, 100 Khz or so, much
higher than human hearing, was recorded along with the normal signal, the magnetic particles did a better
job of recreating the higher frequencies.
It is a complicated process and there are lots of things to go wrong! The tape machine must be
mechanically and electronically aligned to very fine specifications. First, to ensure that it physically
handles the tape gently during shuttling, rewind and fast forward. Although tape formulations have
improved greatly over the years, mechanical problems can damage the tape by stretching or wrinkling it.
There is no error correction for this! Treat your tapes with care and respect. Other problems include loss of
particles off the tape, called shedding, speed fluctuations which produce "wow and flutter" and improper
tape to head contact.
Furthermore, the electronics have to record the input signal and play it back faithfully. This is where tones
on your master tapes becomes so important. They are required to properly align the electronics in the tape
machine so when you work at different studios, your tape sounds like you remembered. When all these
parameters are aligned correctly, you stand a good chance of hearing back a reasonable facsimile of what
you recorded previously.
b. The Digital Recording Process
The digital recording process is far simpler mechanically, but much more involved electronically. The
input signal is sampled 1000's of times per second and each acoustic slice is given it's own digital number,
consisting of 0's and 1's. Theoretically, the "analog-to-digital converter" (ADC) recieves the analog input
and converts it into a stream of numbers and conversely, the "digital-to-analog converter" (DAC) reverses
the process.
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