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English --
EQUALIZER
Low Cut Filter (High-Pass)
The low-cut (or high-pass) filter allows all frequencies
above its cutoff point to pass from filter input to filter output
without attenuation, while frequencies below the cutoff are at-
tenuated (see right). The cutoff point is defined as the frequen-
cy where the signal has dropped 3 dB relative to the flat, or
bandpass, region. Below the cutoff point, the filter exhibits in-
creasingly more attenuation as the frequency diminishes. The
AMS8100 has an adjustable-frequency, low-cut (high-pass)
filter of 6 dB per octave.
Low-cut filters are ideally used for attenuating, or rolling
off, the audio signal where extraneous noise, excessive prox-
imity effect, or other unwanted material is present. For exam-
ple, the low-frequency vibration cause by footsteps and ve-
hicle traffic can be transmitted through microphone stands to
the microphone, and then into the sound system. These fre-
quencies, typically ranging from 5 to 80 Hz, are generally not
desirable.
High-Frequency Shelving
The fixed-frequency equalizer produces a 6 dB boost or
cut at 5 kHz and above (see right). High-frequency shelving is
extremely useful for boosting flat frequency response, temper-
ing very sibilant vocal microphones, or enhancing the sound of
off-axis lavalier microphones.
LOW-CUT FILTER EFFECTS
-10
-8
-6
-4
-2
0
+2
20
100
1,000
5,000
FREQUENCY (Hz)
FULL CW
FULL CCW
50%
ROTATION
HIGH-FREQUENCY SHELVING EFFECTS
200
-10
-8
-6
-4
-2
0
+2
+4
+6
+8
+10
1,000
10,000 20,000
FREQUENCY (Hz)
FULL
CW
FULL
CCW
50%
ROTATION
LIMITER
The AMS8100 has a peak output limiter that prevents dis-
tortion during loud program peaks without affecting normal
program levels. Increasing the individual or Master level con-
trols will increase the average output and, in turn, the amount
of limiting. A limiter prevents excessive overloading of devices
connected to the AMS8100 output. As supplied, the limiter is
defeated. The limiter threshold is selectable for a peak output
level of +4, +8, or +16 dBu. For instance, with the threshold set
at +16 dBu, the mixer would have 12 dB of headroom with a
nominal level of +4 dBu. The limiter thresholds can be changed
from their factory settings as described in the
Internal Modifi-
cations
section.
USING AN EQUALIZER/FEEDBACK CONTROLLER WITH AN AUTOMATIC MIXER
When setting up a sound system which has an outboard
equalizer or feedback controller in the signal chain, set the
AMS8100 to MANUAL. This activates all microphone inputs,
so every possible feedback path is open. With the AMS8100 in
MANUAL mode, equalize the sound system and/or “Ring Out”
the room to set the feedback controller.
After equalization is complete, set the AMS8100 to
AUTOMATIC mode. Remember that the input of an automatic
mixer drops by 3 dB every time the number activated inputs
doubles. When using an AMS8100 in MANUAL mode, the
master output drops by 9 dB when all 8 inputs are activated.
Conversely, it will rise by 9 dB when switched back to AUTO-
MATIC mode.
