13
Shortcut
: To toggle phantom power without entering the menus, press and hold the tone key then
press the menu key for channel 1. Channel 2 phantom can be toggled by pressing the tone key then
pressing the HDD key. If the inputs are in line level mode, phantom power will not activate from the
shortcut keys and must be activated from the menus. Phantom power is linked when the inputs are
linked.
(See Input Linking)
Input Limiters (mic-level only)
Microphone inputs 1 and 2 each have a limiter circuit designed to prevent input overload. In nor-
mal operation, with proper gain settings, the limiters should rarely engage. When activated, these
limiters will prevent unusually high input signal levels from clipping the analog input stage of
the preamp. The front panel LIM LED (
) shows that the limiter is engaged. Limiter activity is
indicated by additional front panel LEDs, one for each input channel (
). The input limiters are
active only with mic-level inputs. The limiters are engaged by (factory) default.
When limiters are engaged, audio on channels 1 and 2 is limited to
-
6 dBFS.
Microphone Level Control
Microphone gain is controlled by the front panel recessed knobs. The gain control adjusts an analog
gain stage and functions similarly to the input trim on a mixing console or stand-alone microphone
preamplifier. Gain is controllable over two ranges, normal and low.
Gain Range (microphone-level only)
The microphone inputs operate in four gain ranges,
NORMAL
,
NORMAL FADES TO OFF
,
LOW
, and
LOW FADES TO OFF
. The
NORMAL
range controls input gain from 24.3 dB to 67.4 dB of gain.
The
LOW
range controls input gain from 9.3 dB to 52.4 dB. The
LOW
ranges are useful for high
SPL recording environments. The fade to off options allow for fader-like control of your gain.
NORMAL FADES TO OFF
provides a gain range of off or 0 to 67.4 dB and
LOW FADES TO OFF
pro-
vides a gain range of off or 0 to 52.4 dB.
High-Pass Filters (microphone-level only)
The high pass filters on the microphone inputs use a combination of analog and digital filters to re-
duce sensitivity to low frequency signals. When the high-pass is engaged on an input, its front-panel
LED illuminates to indicate it is active (
). The first pole of the high-pass circuit is an analog filter
at 40 Hz, 6 dB per octave and is part of the microphone preamplifier circuit. Additional poles of
high-pass filtering are done in DSP.
Several frequency and slope combinations are selectable, including corner frequencies of 40, 80, 160,
or 240 Hz, and filter slopes of 12 dB, 18 dB, or 24 dB per octave. The high-pass is selected for each
input independently.
Shortcut
: The filters can be toggled with a two-key combination. Press and hold the
LCD back-
light key and press the
menu key for channel 1 high-pass. Press and hold the
LCD backlight
key and press the
HDD key to toggle channel 2 high-pass. The high pass filters are linked when
the inputs are linked.
(See Input Linking)
Line-Level Gain Control
When in line-level position, the gain for inputs 1 and 2 is controlled by the front panel recessed
potentiometers or by a menu sensitivity setting. When set for front panel control in the user menu,
LINE INPUT 1: GAIN
and
LINE INPUT 2: GAIN
controls in the user menu are lined out and not acces-
sible.
Summary of Contents for 744T
Page 2: ...backside front cover ...
Page 6: ......
