Handbook for Sound Engineers

826 Chapter 25

system is to facilitate the transfer of a signal from one
source—be it a simple transducer or another system—to
a destination.

Of course things get a bit more involved than that,

and to demonstrate this complexity, the evolution of

what is probably the most important subsystem to our

industry—the recorder, mono, stereo, or multi-

track—will be used to explain how it, almost

single-handedly, made everything as complicated as it is

today. Disks were permanent. You got it right or you

didn’t. Tape at least gave the chance of one more take.

Mixing in the early days of system development was

surprisingly easily achieved—just connecting the

outputs of the various source input amplifiers together

did it perfectly adequately. It’s important to understand

that the technology of the day facilitated this simplicity

far more, paradoxically, than today’s gear. Tube ampli-

fiers, such as were then used, needed to be terminated at

their outputs by a specific impedance for proper opera-

tion, which for reasons discussed later was universally

600 : floating balanced. By simply connecting ampli-

fier outputs together, a mix of sources was achieved,

provided each of the source amplifiers saw 600:. It

was only a very minor step for interspersed networks to

become constant-impedance variable attenuators,

usually in the form of rotary controls. The pot (from

potentiometer) or fader was born. The ability to create a

balance of sundry sources for the chosen destination is

perhaps the most recognized feature of the console and

its system. Convention and common sense rule this as

the main signal path, and other paths are subsidiary or

auxiliary to it.

25.2 Auxiliary Paths

25.2.1 Monitoring

Take the example of Fig. 25-6, where a single micro-

phone is being laid on a recorder. It’s operationally

necessary for the system operator to hear the signal

going to the recorder with headphones or a

control-room monitor loudspeaker. To facilitate this

requirement, a parallel feed is taken off the machine

input to the operator’s monitor. Monitoring is perhaps

the most important of the auxiliary signal paths; upon it

is based the qualitative decisions of the nature of the

signal in the main path. It is the reference.

Fig. 25-7 applies a small extension to the basic

monitoring path in the form of a source/replay switch,

enabling operators to hear the aftermath of their efforts.

If the recorder has separate record and play signal paths,

they can even toggle between the two while actually

recording for immediate quality assessment. The moni-

toring section is born.

Figure 25-1. Mechanical recording or early drum recording.

Figure 25-2. Electrical recording (disk cutter driven by
electricity).

Figure 25-3. Public address system.

Figure 25-4. Disc replay.

Figure 25-5. Simplified broadcast system.

Sound Diaphragmwith stylus

Rotating

wax drum

Helical cut in

cylinder

modulated

by sound

Drive

screw

Acoustic

horn

MicrophoneAmplifier Disk cutter

Microphone AmplifierLoudspeaker

Phono

pickup

Amplifier Loudspeaker

Source

switch

Transmitter

Antenna