Mackie 8-BUS Series, Руководство пользователя

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D i g i t a l 8 • B u s
Glossary
A-4
dropping?) the signal can be –70 dBu or lower.
It is also possible for some microphones to de-
liver more signal than this, in which case it
may be referred to as a “hot” mic level. Alter-
natively, you can just say, “Boy, is that loud!”
mic preamp
Short for microphone preamplifier. An ampli-
fier that functions to bring the very low signal
level of a microphone (approximately –50 dBu)
up to line level (approximately 0 dBu). Mic
preamps often have their own volume control,
called a trim control, to properly set the gain
for a particular source. Setting the mic preamp
gain correctly with the trim control is an essen-
tial step in establishing good noise and
headroom for your mix.
MIDI
Acronym for musical instrument digital in-
terface. MIDI is the music industry’s standard
serial communication protocol.
Nyquist Sampling Theorem
An incoming analog signal must be con-
verted to a digital signal before the Digital
8•Bus can do its thing. The amplitude of the
analog signal is sampled at a fast rate and con-
verted into digital words.
The theorem states that a continuous ana-
log signal must be sampled at a frequency
higher than twice the highest analog frequency
present in order to be accurately reproduced,
or aliasing will occur. Filtering of the signal be-
fore sampling will reduce aliasing errors (see
aliasing ).
parametric EQ
A “fully” parametric EQ is an extremely pow-
erful equalizer that allows smooth, continuous
control of each of the three primary EQ param-
eters (frequency, gain, and bandwidth) in each
section independently. “Semi” parametric EQs
allow control of fewer parameters, usually fre-
quency and gain (i.e., they have a fixed band-
width, but variable center frequency and gain).
PFL
An acronym for Pre Fade Listen. Broadcast-
ers would call it cueing. Sound folks call it being
able to solo a channel with the fader down.
phantom power
A system of providing electrical power for
condenser microphones (and some electronic
pickup devices) from the sound mixer. The sys-
tem is called phantom because the power is
carried on standard microphone audio wiring in
a way that is “invisible” to ordinary dynamic
microphones. Mackie mixers use st48
volt DC power, switchable on or off. Most qual-
ity condenser microphones are designed to use
+48 VDC phantom power. Check the
manufacturer’s recommendations.
Generally, phantom power is safe to use with
non-condenser microphones as well, especially
dynamic microphones. However, unbalanced
microphones and some electronic equipment
(such as some wireless microphone receivers)
can short out the phantom power and be
severely damaged. Check the manufacturer’s
recommendations and be careful!
phasing
A delay effect, where the original signal is
mixed with a short (0 to 10 msec) delay. The
time of the delay is slowly varied, and the
combination of the two signals results in a dra-
matic moving comb-filter effect. Phasing is
sometimes imitated by sweeping a comb-filter
EQ across a signal. A comb filter can be found
in your back pocket.
phone jack
Ever see those old telephone switchboards
with hundreds of jacks and patch cords and
plugs? Those are phone jacks and plugs, now
used widely with musical instruments and audio
equipment. A phone jack is the female connec-
tor, and we use them in
1 ⁄
4
" two-conductor (TS)
and three-conductor (TRS) versions.
phone plug
The male counterpart to the phone jack, de-
scribed above.
post-fader
A term typically used to describe an aux
send that is connected so that it is affected by
the setting of the associated channel fader.
Sends connected this way are typically (but not
always) used for effects. See
pre-fader .
pre-fader
A term typically used to describe an aux send
that is connected so that it is not affected by the
setting of the associated channel fader. Sends
connected this way are typically (but not always)
used for monitors (foldback). See
post-fader .
Q (bandwidth)
A way of stating the bandwidth of a filter or
equalizer section. An EQ with a Q of .75 is
broad and smooth, while a Q of 10 gives a nar-
row, pointed response curve. To calculate the
value of Q, you must know the center fre-
quency of the EQ section and the frequencies
at which the upper and lower skirts fall 3 dB
below the level of the center frequency. Q
equals the center frequency divided by the dif-
ference between the upper and lower –3 dB
frequencies. For example, a peaking EQ cen-
tered at 10kHz whose –3 dB points are 7.5kHz
and 12.5kHz has a Q of 2.
quantization
The digital representation of an analog sig-
nal involves sampling the amplitude at a fast
rate. Quantization is the measurement of the
amplitude at the time of each sample, expressed