Audio Technica AT-MX381 SmartMixer Installation And Operation Manual page 3

Please Note!
This manual assumes use of microphone-level inputs and line-level output, the
most typical SmartMixer application. However, all inputs and the output may be
individually switched via the included SmartMixer Software to achieve any
combination of mic- and line-level input/output. Refer to Software Manual for
more information.
About the AT-MX381 SmartMixer
Audio-Technica's AT-MX381 SmartMixer is a microprocessor-controlled, pro-
grammable, automatic-switching eight-channel audio mixer. It can be used
with low-impedance dynamic and condenser microphones (including wireless
microphone systems), as well as with line-level sources.
The AT-MX381 is designed to improve audio quality in broadcast, sound-rein-
forcement and recording applications. One of the ways it achieves this is by
keeping the number of open microphones to a minimum, thus reducing back-
ground noise, feedback and other distractions, while providing instant, com-
pletely transparent switching between channels.
Each of the AT-MX381 SmartMixer's eight balanced inputs provides switchable
48-volt phantom power; attenuation is also selectable on each input to allow
use with line-level signals. The mixer's main output is balanced and non-invert-
ing. In addition to a single main output, individual direct outputs are provided
for each input channel. All audio connections terminate in block screw con-
nectors.
Up to 16 AT-MX381 SmartMixers (a total of 128 channels) can be daisy-chained
via the included Link Cable, which carries control bus, audio, and configuration
data between mixers. Multiple mixers linked in this way will operate as if they
were a single mixer. Therefore, microphones activated on any mixer will cause
the appropriate switching functions to occur. Due to the link data protocol
(used for computer control and external RS232 control), AT-MX351 and AT-
MX341a SmartMixers cannot be linked to AT-MX381 SmartMixers.
The AT-MX381 includes two separate external control systems: Individual-
channel contact closures (via DB25 connector) and PC control (via RS232 con-
nector). The RS232 connector can also be used to connect an external control
system (Crestron® or AMX®) using "open disclosure communication proto-
col" to control the SmartMixer.
Overview of AT-MX381 Features
• Eight balanced inputs allow use with both mic and line-level signals. Each
input provides:
48V phantom power (individually selectable)
°
Individual gain and sound volume controls
°
Gate attenuation adjustable (0 dB to full mute in steps of 12 dB)
°
Low-cut filter (individually selectable via SmartMixer Software) to
°
minimize the pickup of undesirable noise
• NOMA (Number of Open Mics Attenuated) (selectable)—Automatic gain
adjustment as each microphone is activated
• Selectable manual mode overrides automatic functions
• Selectable hold time allows mics to stay on during brief pauses in conver-
sation
• Linking capability for 16 units (up to 128 channels)
• External control capability enables the SmartMixer to activate other
devices
• An RS232 data port provides a connection point for a PC computer running
the SmartMixer Software to configure key operating functions.
• Compatible with Crestron® or AMX® systems
• Output level meter
• Monitor headphone output with level control
• Basic functions are set on the main unit; detailed setting through
SmartMixer Software
• Mounts in a single 19" rack space; includes rack mount adapters
I I n n t t r r o o d d u u c c t t i i o o n n
Priority Pre-select
To custom-tailor conferencing needs, the mode of each microphone channel
can be independently switched. The combination of switch settings results in
three different modes of priority selection/operation. (See page 5, "Priority
Microphones and the Lockout Bus.")
Last Mic On
In any of the three modes of operation, the last microphone "on" will remain
"on" when talking ceases, to provide continuous room ambience. This feature
is cascaded throughout all linked mixers so that only one microphone in the
entire system will remain on.
Gate Attenuation
When a microphone is "off," its input is only attenuated. This attenuation is
factory set at -36 dB. The amount of "off " attenuation (gate attenuation) can
be adjusted via SmartMixer Software. (See page 5, "Adjusting Gate
Attenuation.")
Manual (Non-automatic) Mode
If the automatic functions are not desired, the SmartMixer can be placed in
manual mode, bypassing the mixer's automatic switching and attenuation
functions, causing the unit to behave like a conventional mixer. In manual
mode, the level of each input is controlled via its front panel gain and level
controls.
NOMA (Number of Open Microphones Attenuated)
In a multiple-microphone system, as more microphones are turned on
(opened), the increased system gain can be a potential source of feedback.
The NOMA feature helps control feedback by compensating for the increase
in system gain. A built-in algorithm in the AT-MX381 recognizes how many
microphones are "on" and automatically adjusts the system gain accordingly.
Because use of NOMA is not always appropriate or desired, the AT-MX381 is
shipped with the NOMA function disabled. Refer to Software Manual for
instructions on enabling NOMA.
External Control Connector (25 Pin D-Sub)
To increase the integration flexibility of the AT-MX381 with external control
and indicator devices, a rear panel connector (25-pin) is provided. Three func-
tions are available for each input channel via this connector:
1. "Force-On" – allows an external contact closure to force its
associated input to turn on.
2. "Force-Off – allows an external contact closure to force its
associated input to turn off.
3. "Control Voltage Out" – a voltage appears when the associated
input's gate opens or turns "on".
Note: External contact closures override PC control.
Refer to the section "External Logic Switching & Control Voltage" on page 6
for additional information.
RS232 Control Port
A rear panel RS232 port (9-pin) is provided to allow for the connection of a
computer running the SmartMixer Software application or external control
system (Crestron® or AMX®) using open disclosure communications proto-
col. Refer to Control Function Table on Page 4 for information on items con-
trolled by the computer.
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