Handbook for Sound Engineers

Consoles 827

25.2.2 Prefade Listen and Audition

When a multiple-source system is established (similar
to Fig. 25-8), another monitoring requirement, prefade
listen (PFL) and audition, is required. Imagine the case
of a radio broadcaster, where the sources consist of disk
replay units and microphones; it’s an obvious necessity
to be able to listen to a source prior to its being put on
air to check that:

1. The microphone is set at the correct position, level,
   or even working!


2. The required section of a disk or tape is cued up or
   ready to play.

There are two basic methods of arranging this
prehear function, as shown in Fig. 25-9. They owe their

existence primarily to slightly different operating prac-

tices on opposite sides of the Atlantic. The first, Fig.

25-9A, involves switching the signal immediately prior

to the fader on the selected source path into the moni-

toring chain. This is called prefade listen (PFL). A

useful but not immediately obvious virtue of this

arrangement is that it is possible to listen to a channel’s

contribution to a mix of which it is part without

disturbing that mix. It is, therefore, a nondestructive

monitoring function. The alternative method shown in

Fig. 25-9B consists of removing the required channel

(postfader) from the mix and placing it onto a second

parallel mix facility, commonly called audition or

rehearse; it is possible in this mix to emulate exactly

what would happen in the real mix without upsetting the

presently active mix. A disadvantage of this method is

the inability to use the function when the channel is live

because it disrupts that source and prevents it from

going to the mix. It is a destructive monitoring tech-

nique. Each method has its virtues, though, and most

modern consoles use both techniques to varying extent.

That said, all but really small American broadcast

consoles nowadays employ a PFL-type cue function, the

audition/rehearse bus being arranged to be a secondary

mix bus independent of but in the same vein as the

program bus. The name often remains as an echo of its

original function. Postfader monitoring, however, lives

on in large production consoles as in-place stereo moni-

toring, described later.

Figure 25-6. Simple microphone-to-recorder monitoring
(source only).

Figure 25-7. Recorder monitoring (source and tape).

Figure 25-8. Multisource mixer.

Tape recorder

Monitoring headphones

Replay B

Source A

Mixing bus

Faders Mixing amplifier

Output

Figure 25-9. Prefade listen (PFL) and audition.

A. Prefade listen.

B. Audition.

Prefade listen

switch

Main

Audition

Main mix amp

Output

Main

PFL

PFL mix amp

Main

Audition

Main mix bus

PFL bus