User Manual

Scorpio Preliminary User Guide
29
pan
When a channel is routed to a stereo-linked bus the level it appears at
each bus is adjusted by a pan control. A channel with its pan control
“straight up the center”, or “centered” sends signal at the same level
to each bus. A channel that is panned left or right sends the signal to
the left or right bus, respectively.
mute
A mute control is a convenient on/off switch for a channel and an
easy way to remove a channel from appearing in downstream buses.
Muting an input or channel does not change levels or settings; when
channels are muted and unmuted, their settings remain.
polarity (audio)
The direction of the current ow of an audio signal is dened as po-
larity. The polarity of a signal can be reversed when a balanced audio
signal connection has its pin-2 and pin-3 connections reversed. Sin-
gle-ended signals can have their polarity reversed when going through
an “inverting” gain stage. It is best practice to have all incoming and
outgoing signals with the same polarity relationship.
phase
The relationship one audio signal has in time with respect to another
audio signal is dened in degrees of phase. When audio signals are
generated at identical times, they are “in phase” with each other.
When one audio signal is time-delayed with respect to another, the
signals are “out of phase”. Differing phase relationships can be
introduced several ways, including when microphones are placed at
varying distances from a sound source, or electrical/digital delay is
introduced to one signal with respect to another.
input limiter
A limiter circuit reduces the peak signal levels of audio, generally to
prevent signal overload. Analog inputs have a maximum input signal
level that can be reached before overload/distortion is introduced.
Setting the input gain correctly so that input signals do not reach this
maximum level prevents most overload conditions. In the presence of
very high, unexpected signals an input limiter changes the gain of the
incoming signal and prevents it from overloading. Input limiters are
sometimes compressor-type circuits with a ratio of innity:1, mean-
ing that any increase to the input signal into the limiter at the limiter
threshold does not increase the output signal of the limiter.
Several parameters may be available in a limiter, including knee, ratio,
release, and threshold.
HPF, high pass lter (audio)
Also referred to as a low-cut lter, this circuit reduces the amount of
low frequency content in an audio signal. A HPF is particularly useful
when recording speech since the human voice does not generate
appreciable energy at low frequencies. The HPF reduces non-speech
signals such as environmental noise, wind noise, and microphone
handling noise, improving the intelligibility of speech and reducing low
frequencies from overloading the input. The high pass lter is placed
in the circuit close to the microphone preamplier.
High pass lters are often frequency selectable, ranging from 20 Hz to
200 Hz. HPF also have a slope, generally from 3 dB/octave to 18 dB/
octave. Greater/steeper slopes offer more attenuation of frequencies
just below the set lter frequency.
low cut lter
See high pass lter.
PFL, pre-fade listen
When an input or channel is selected for monitoring/solo with a PFL,
the channel is routed to the headphone output before the channel
fader so that the fader position has no effect on the headphone level.
Trim/gain changes to the input will change the headphone output.
solo
A control on a mixer to route a channel to headphones while muting
all others. Solo and PFL are related controls and in many consoles are
the same. Solo circuits can be exclusive—only one channel is sent to
headphones at a time—or non-exclusive—any number of channels can
be sent to the solo circuit and appear in headphones.
trim
Also dened in mixers as “gain”, the trim adjustment is the rst stage
of gain of a microphone or line level input. Typical microphone trim
values range from 10 dB to 50 dB, depending on microphone sensi-
tivity and volume of the sound source.
fader
A physical control on a mixing console, either a rotary or sliding po-
tentiometer, that controls the level of a channel to a bus. Most faders
have more attenuation than gain available and a unity gain position
where the input trim level established the level to the bus.
slate microphone
A microphone, built-in or external, on an audio mixer used to notate
takes or communicate with sound team members by the mixer’s user
speaking into the microphone. Slate microphones are often routable
to buses or tracks.
pre-roll
A continuous buffer that is always writing to memory offering a record-
ing that begins prior to when the record button is activated. Pre-roll is
set in seconds, and the recording begins the set number of seconds
prior to the button being pressed. This is helpful in applications where
an operator missed a cue to begin recording.
gain
An increase (or decrease with negative gain) in the level of an audio
signal. Gain can be applied in several locations, to both analog and
digital signals. In a eld mixer, the microphone preamplier provides a
substantial amount of gain at the trim to raise the low level micro-
phone signal to a usable signal in the mixer. Gain is also available at
the fader. Gain of digital signals or line level analog signals is often
limited. Unity gain is gain stage that neither adds or subtracts level
from a signal.
attenuation
A reduction in the level of an audio signal. Attenuation can be applied
to both analog and digital signals. A fader is used primarily to attenu-
ate signals, though a small amount of positive gain is often available
on a fader.